Corn & Drones: A Practical Field Guide

Agriculture Workflow and Application
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Corn (North America) & Drones: A Practical Field Guide

Introduction

This document serves as both a guideline and a source of inspiration for new users who are new to agriculture or farmers looking to integrate drone technology into their management practices. It is a work in progress, and I welcome any comments, corrections, or ideas for improvement. Although I am not an agronomist by profession, my goal is to continually expand Section 11 with real-world examples and tutorials demonstrating how drones can assist corn growers. By incorporating feedback from experts and practitioners, I hope this resource will remain accurate, relevant, and beneficial to anyone seeking to enhance their farming operations with modern drone applications

Table of Contents

  1. Corn Growth Stages
  2. Field Preparation
  3. Planting
  4. Fertilization and Nutrient Management
  5. Crop Care and Field Management
  6. Input Requirements
  7. Major Pests and Diseases
  8. Seasonal Work Timeline
  9. Mechanization and Technology
  10. Precision Agriculture
  11. Drone Applications in Corn
  12. Literature

Corn Growth Stages

Overview of Vegetative and Reproductive Stages

Corn Growth Stages: Corn development is divided into vegetative (V) stages and reproductive (R) stages. Growth begins at emergence (VE) when the shoot breaks through soil (typically ~5–10 days after planting) and proceeds through a series of leaf stages V1, V2, V3, etc., until the tassel forms at VT (tasseling). Each vegetative stage is defined by the number of leaves with visible collars (e.g. V6 means six leaves fully emerged). Around V6, the growing point emerges above ground and the plant enters rapid growth. The reproductive phase starts at R1 (silking), when silk strands emerge from ears to catch pollen. Pollination occurs at R1, a critical period when moisture or heat stress can severely reduce kernel set. Kernel development follows in stages: R2 (blister) ~10–14 days after silking when kernels are white fluid-filled blisters, R3 (milk) ~18–22 days after silking when kernels contain milky fluid, R4 (dough) ~24–28 days (kernels soft “dough”), R5 (dent) ~35–42 days (kernels dent as starch hardens), and finally R6 (physiological maturity) ~55–65 days after silking when kernels achieve maximum dry weight and a black layer forms at the kernel base. At R6 the crop is harvest-ready after field drying to safe moisture. A typical corn hybrid requires about 100–120 days from planting to maturity depending on relative maturity and environmental conditions. Notably, corn is most sensitive to stress around flowering (VT/R1), which can dramatically impact yield if drought or other stresses occur. Management decisions – from fertilizer timing to pest control – are often guided by growth stage, underscoring the importance of staging corn accurately.

Growth Stage Timeline

Stage Description Timing (days after planting) Timing (days after silking) Additional Information
VE Emergence 5-10 - Shoot breaks through soil
V1 to Vn Vegetative growth From VE to VT - Each stage defined by number of leaves with visible collars; around V6, growing point emerges above ground
VT Tasseling Approximately 45-55 (just before R1) - Tassel is visible
R1 Silking 45-55 0 Silk strands emerge from ears; pollination occurs
R2 Blister 55-69 10-14 Kernels are white fluid-filled blisters
R3 Milk 63-77 18-22 Kernels contain milky fluid
R4 Dough 69-83 24-28 Kernels are soft “dough”
R5 Dent 80-97 35-42 Kernels dent as starch hardens
R6 Physiological maturity 100-120 55-65 Kernels achieve maximum dry weight; black layer forms at kernel base; harvest-ready after field drying

Field Preparation

Tillage Systems and Soil Management

Field Preparation: Modern corn farming uses highly mechanized soil management to ensure a proper seedbed. Corn grows best on well-drained soils; poor drainage can stunt early growth. In many systems, fall tillage (e.g. chisel plowing or ripping) is performed after the previous harvest to manage residue (especially if prior crop was corn) and alleviate compaction. In spring, a secondary tillage pass (field cultivator or disk harrow) may create a fine, firm seedbed. In regions like the Midwest, conventional tillage is common, but no-till and reduced-till practices are also widely used – roughly one-third of corn acreage in the U.S. is no-tilled. No-till planting into undisturbed residue can be successful if fields are well-drained and equipped with planter attachments (row cleaners, coulters) to cut through debris. Advantages of no-till or minimal tillage include moisture conservation and reduced erosion, but soils may warm more slowly in spring. Some areas (e.g. the Mid-South) use raised beds prepared in fall to improve spring soil warmth and drainage. If compaction layers exist, subsoiling (deep ripping) is done pre-plant to break hardpan restrictions. Overall, field prep aims to balance residue management with soil structure. Many corn growers apply fertilizers or manure during field prep (fall or early spring) so nutrients are in place at planting. For instance, anhydrous ammonia (nitrogen) might be injected in fall or pre-plant in spring on tilled fields. Lastly, a pre-plant burndown herbicide is often sprayed to kill winter weeds, ensuring a clean start at planting. By planting time, the soil should be moist, free of large clods, and at least 50 °F (10 °C) at 2-inch depth for good germination.

Planting

Timing and Equipment

Planting: Corn planting in the U.S. is typically done in spring (generally April through May, varying by latitude). Farmers aim to plant as early as conditions allow, since earlier planting (late April in the Corn Belt) usually maximizes yield potential. Soil temperature is a key indicator – a consistent 50–55 °F at 2 inches deep for a few days is recommended for planting to ensure prompt germination. Planters are large, precision machines (often 12–24 rows wide, covering 30–60 feet/9–18 m per pass) equipped with GPS guidance for straight, accurate rows. Seed depth is set about 1.5 to 2 inches (3–5 cm) for corn to reach moisture; planting deeper than ~3 inches can delay emergence.

Population and Row Spacing

Plant population is managed carefully to optimize yield. Typical seeding rates are on the order of 30,000–34,000 kernels per acre for rainfed corn, and can exceed 34k in high-yield or irrigated environments. For example, Nebraska data suggest ~34,000 seeds/acre for irrigated corn and 24,000–30,000 for dryland, as optimal for profit. Modern hybrid corn seed has high germination rates (≈95%), so planters are often calibrated to drop ~5% more seeds than the target final stand. Row spacing is usually 30 inches (0.76 m) between rows – the industry standard which research shows provides highest yields in most regions, whereas wider 36–40" rows can reduce yield ~10–15%. Precision planters use singulating meters to ensure uniform intra-row spacing, since uneven spacing or doubles can hurt yields. A rule of thumb is to avoid planting too fast; studies show that increasing planter speed from 4 to 7 mph can increase seed spacing variability and cut yields by ~10%. In practice, many farmers plant around 4–6 mph, checking seed depth and spacing frequently. Seeds are often delivered in treated form – coated with fungicides (and sometimes insecticides) to protect against seedling blights and soil pests during germination. Within 1–2 weeks of planting, corn emerges and a successful stand is assessed (for instance, ~32,000 healthy plants/acre might be the goal for a planned 34,000 planting). Any major shortfall in emergence could prompt replant decisions, though this is uncommon with proper conditions.

Fertilization and Nutrient Management

Nutrient Requirements and 4R Principles

Fertilization and Nutrient Management: Corn has high nutrient requirements, especially for nitrogen. A 150–200 bushel/acre corn crop will uptake on the order of 135–180 lbs of N, 50–70 lbs P₂O₅, and 40–50 lbs K₂O per acre in the grain alone. To support such growth, farmers apply fertilizers following the “4R” principles (right Rate, Source, Timing, Placement).

Nitrogen Management

Nitrogen (N) is the most critical and typically the largest fertilizer input for corn. Historically, extension guidelines often recommended ~1.2 lbs N per expected bushel of yield for corn after corn (so ~180 lbs N for a 150 bu yield goal, more if following corn or wheat). However, modern recommendations use economic optimum N rates and credits for N from soil and previous crops. For example, if corn follows soybean, the soybean can supply ~30–50 lb N/acre via residual mineralization (a “soybean credit”), so less fertilizer N is needed. In practice, many Midwest farmers apply around 150–200 lb N/acre for corn after soy, and 180–240 lb N/acre for corn after corn, adjusted for yield potential and soil nitrate levels. Timing is important: some N may be applied in the fall (as anhydrous ammonia in colder climates) or pre-plant, and additional N is often side-dressed at V6–V8 (about 4–6 weeks after emergence) to ensure N availability during peak uptake (around V8 through tasseling). This split application reduces leaching risk and aligns N supply with crop demand.

Phosphorus, Potassium, and Other Nutrients

Phosphorus and Potassium are applied according to soil tests. Corn’s grain removes about 0.37 lbs P₂O₅ and 0.27 lbs K₂O per bushel. Thus a 180 bu crop takes ~67 lb P₂O₅ and 49 lb K₂O out of the soil in grain; additional amounts reside in stover. If soil test levels are low or medium, farmers will apply P and K (often in fall or pre-plant) to build or maintain fertility. For example, a common approach might be broadcasting 50–100 lb P₂O₅ and K₂O per acre before corn planting if needed, or banding some P (10–20 lb P₂O₅) as a starter fertilizer at planting. Starter fertilizer (placed 2 inches beside and below the seed) is popular in corn production, especially in cooler soils, as a small dose of N and P near the seed can boost early growth. Zinc is another nutrient occasionally applied (in starter or broadcast) if soil tests indicate deficiency, since corn can suffer from Zn deficiency in high-pH or cold soils. Lime may be applied in preceding seasons if soil pH is acidic (<6.0), as corn prefers pH ~6.0–6.8 for optimal nutrient availability. Overall, corn fertilization is often fine-tuned with precision technology: for instance, variable-rate N application based on productivity zones or using crop sensors (like NDVI) to adjust in-season N. With these practices, a well-fertilized corn crop can accumulate enormous biomass; by silking, about half of total N and dry matter is already taken up, and nutrient uptake peaks during grain fill. Efficient nutrient management is crucial not only for yield and profit, but to avoid environmental losses of N (leaching or gaseous loss) and P (runoff).

Crop Care and Field Management

Weed Control Strategies

Crop Care and Field Management: Once corn is planted and growing, farmers implement various care practices throughout the season. Weed control is a major focus in early to mid-season, as corn does not compete well with weeds in the first ~4–6 weeks. Most conventional corn fields use herbicides in a program approach. Typically a pre-emergence herbicide is applied near planting (or soon after) – for example, atrazine-based mixtures, acetamides (like acetochlor, metolachlor), or herbicides like mesotrione – to provide residual control of grasses and broadleaf weeds as the corn emerges. Then, a post-emergence spray is often done around V3–V5 (3–5 leaf stage), which may include glyphosate (for glyphosate-tolerant “Roundup Ready” corn hybrids) or other selective post herbicides to kill any emerged weeds. Many programs “layer” residual herbicides by including a second residual in the post spray to extend weed control through canopy closure. This two-pass strategy effectively keeps fields weed-free into mid-season. In some cases, if weeds break through later, a clean-up spray or even mechanical cultivation can be employed, but this is less common with good herbicide programs. Common weeds like foxtails, waterhemp, lambsquarters, and ragweeds are thus managed to prevent yield loss and avoid weed seed production.

Insect Pest Management

Insect pest management in corn has been greatly aided by biotech (Bt) traits, but scouting is still important. Key insect pests include early-season soil pests (seedcorn maggot, white grubs, wireworms, cutworms) which can reduce stands – these are largely controlled by seed treatments and occasionally soil-applied insecticide in high-risk fields. European corn borer and corn earworm were historically serious pests, but Bt corn hybrids targeting these insects have vastly reduced their impact (Bt proteins like Cry1Ab, Cry1F, etc. protect against borers, and newer Vip3A traits against earworm). Corn rootworm (CRW) remains a major pest in continuous corn – larvae feed on roots in early summer, causing lodging. Many corn hybrids carry Bt rootworm traits, but due to evolving resistance in some CRW populations, farmers often implement crop rotation (rotating to soybean or other crops breaks the rootworm life cycle) and/or use soil insecticides or rotated Bt modes of action to manage CRW. Other potential pests are armyworms or cutworms that can chew seedlings (sometimes managed by insecticidal seed treatments and scouting), and sap feeders like corn leaf aphids or spider mites (mite outbreaks can occur in drought conditions or after insecticide use that kills predators). In high-value or seed production corn, aerial insecticide sprays might be used if thresholds are exceeded, but in field corn this is relatively rare thanks to Bt traits and IPM practices.

Disease Management

Disease management is also critical, particularly foliar and stalk diseases in mid to late season. Common corn diseases include Gray Leaf Spot (fungal leaf blight), Northern Corn Leaf Blight, Southern Rust (in southern states), and stalk rots (like Anthracnose or Fusarium stalk rot). These diseases are favored by humid or wet conditions and can reduce photosynthetic leaf area or cause stalk lodging. The first line of defense is planting hybrids with disease resistance and practicing crop rotation (many pathogens overwinter on corn residue). Additionally, foliar fungicides are often applied at tasseling (VT) or silking (R1) if disease pressure is high. For example, in the Corn Belt it’s become common to spray a fungicide around VT–R1 to protect against Gray Leaf Spot and other leaf diseases on susceptible hybrids, particularly in no-till fields with heavy residue inoculum. This can improve late-season plant health and sometimes yields. Farmers scout around V10–VT for disease lesions on lower leaves and decide on fungicide applications. Stalk rot management involves ensuring plants are healthy (adequate potassium, avoiding excessive plant population or nitrogen that can lead to weaker stalks) and harvesting on time if stalk quality is declining.

Irrigation and Water Management

Another aspect of crop care is irrigation in regions that need it. Corn has high water needs – a full season crop uses roughly 20–28 inches (500–700 mm) of water from planting to maturity. Peak water use occurs around tasseling to milk stage, when a corn field can consume ~0.25–0.3 inches per day. In the western Corn Belt and Plains (e.g. Nebraska, Kansas, Texas), center-pivot irrigation is widely used to supply water and avoid drought stress during these critical periods. Scheduling irrigation is done by monitoring soil moisture or crop evapotranspiration rates, aiming to not let the crop suffer during flowering and grain fill (stress during R1 can cause kernel abortion, and during R3–R5 can reduce kernel weight). Modern pivots with variable-rate irrigation can even apply different amounts of water to zones of a field based on soil water-holding capacity. Apart from weeds, insects, diseases, and water, other corn care tasks include side-dress fertilization (as noted, many farmers side-dress N around V6 using high-clearance equipment or injection rigs), tissue testing (at V5 or VT to diagnose any micronutrient deficiencies), and scouting in general – fields are monitored regularly for any emerging problems so that interventions (spraying, etc.) can be made in a timely fashion. By late summer, the focus shifts to preparing for harvest.

Input Requirements

Seeds and Planting Materials

Input Requirements: High-yield corn under mechanized management is input-intensive. Seeds: Corn uses hybrid seed that is purchased each season. Seeding rates average on the order of 30–35 thousand seeds/acre, which at typical planting rates means about 2–3 acres planted per seed bag (80k kernels per bag). Seed cost can be significant (often $100–$150 per acre for traited hybrids). Seeds come pre-treated with protectants (e.g. insecticidal clothianidin + fungicides against Pythium, Fusarium, etc.) to ensure good stand establishment.

Fertilizer Requirements

Fertilizer: Nitrogen is the largest nutrient input – for example, ~0.9–1.1 lbs N per bushel yield target. A 200 bu/ac corn might receive ~180 lbs N/acre (split between ammonia, urea, or UAN applications). Phosphorus and potassium inputs depend on soil fertility; many Corn Belt soils have moderate P and K levels from historical manure or fertilizer, but to sustain removal, a 200 bu crop may get on the order of 50–60 lbs P₂O₅ and 40–80 lbs K₂O per acre if soil tests are medium. Secondary nutrients like sulfur are increasingly applied (e.g. 10–20 lbs S/acre via gypsum or ammonium sulfate) since higher yields and cleaner air (less atmospheric S) have led to more S deficiencies. Corn also requires micronutrients in small amounts (Zn, boron, etc.), which are applied if soil or tissue tests show need.

Water and Irrigation

Water: Corn’s water requirement (~25") is often met by natural rainfall in the eastern Corn Belt, but irrigated corn will use substantial water – for instance, a center pivot covering 130 acres may apply 5–15 inches of water through a season depending on rainfall. This translates to millions of gallons (1 inch/acre ≈ 27,154 gallons); thus efficient water management (timing and amount) is crucial in irrigation areas.

Crop Protection Chemicals

Crop Protection Chemicals: Herbicides are a routine input – typically 1–2 applications per season. For example, a pre-emerge herbicide mix might be applied at ~2 pints/acre, and a post spray (like glyphosate) at ~32 oz/acre, plus any needed adjuvants. Insecticides are used more sparingly due to Bt traits, but some farmers apply a pyrethroid with the fungicide at VT as a preventative or to control late-season ear-feeding insects if present. Fungicide use in corn has grown – a common product (strobilurin/triazole mix) applied by air or ground at ~10–15 oz/acre around tasseling.

Labor, Fuel, and Equipment

Labor and Fuel: A large corn operation requires significant machinery use, so diesel fuel is a notable input (tractors for tillage/planting, combines, trucks, etc.). Precision guidance helps reduce fuel waste by minimizing overlap. Human labor per acre is relatively low thanks to mechanization – a single farmer with modern equipment can manage hundreds of acres. Technology and Equipment: While not a “consumable” input, modern corn farming relies on capital inputs like tractors (200–400 HP), planters (with high-tech monitors and controllers), sprayers (90-foot booms with section control), and combines with corn heads. Many farms invest in on-farm grain dryers to dry corn from ~20% at harvest down to ~15% for safe storage, which incurs energy cost (propane or natural gas). In summary, corn demands substantial inputs but returns high yields; efficient input use (through soil testing, integrated pest management, and precision ag) is key to profitability and sustainability.

Major Pests and Diseases

Key Insect Pests

Major Pests and Diseases: Corn in the USA faces a range of pests and pathogens, though many are mitigated by hybrids and management. Among insects, the Western corn rootworm (and Northern corn rootworm in some areas) is notorious – its larvae feed on roots, causing plant lodging and yield loss. It is managed by crop rotation (corn rootworm eggs hatch expecting corn roots each year; a non-corn crop like soybean starves them) and by Bt rootworm-traited corn hybrids or soil insecticides at planting. However, rootworm populations have developed resistance to some Bt proteins, so best practice is to use multiple modes of action and not plant corn-after-corn repeatedly with the same trait. European corn borer (ECB) was historically a huge pest (boring into stalks and ears), but Bt corn targeting ECB has reduced its prevalence by >90%. Non-Bt corn fields or sweet corn may still need scouting; thresholds for treatment depend on egg mass counts and potential damage. Fall armyworm and corn earworm can attack corn ears (especially in the South for armyworm, nationwide for earworm). Bt traits (Vip3A) also provide control of these in many hybrids. Black cutworm is an occasional early-season pest: moths lay eggs in spring and larvae cut down seedlings – insecticide is warranted if ~3% of plants are cut and larvae are present, but often Bt and seed treatments help, plus pheromone traps warn of outbreaks. Corn aphids (e.g. green peach aphid) can infest tassels but usually are minor and controlled by natural enemies. Spider mites (two-spotted spider mite) can flare up in hot, dry weather, especially if broad-spectrum insecticides killed predators; mites cause leaf “speckling” and drying usually along field edges. If severe, miticides may be applied. Overall, corn insect IPM relies on resistant hybrids, rotation, seed treatments, and timely scouting – in most commercial fields, few if any foliar insecticide sprays are needed in a season.

Common Diseases

On the disease side, foliar diseases like Gray Leaf Spot (GLS) and Northern Corn Leaf Blight (NCLB) are widespread. GLS, caused by Cercospora zeae-maydis, produces rectangular gray lesions on leaves, usually starting on lower leaves after silking. If lesions move to upper leaves (ear leaf and above) during grain fill, yield can be cut significantly. Many hybrids have partial resistance, and fungicides at VT–R1 are effective if disease pressure is high. NCLB (caused by Exserohilum turcicum) causes cigar-shaped lesions; its management is similar (resistance and fungicide if needed). Southern rust (Puccinia polysora) is a potentially devastating foliar disease that blows into the southern U.S. from tropical regions – it produces orange pustules on leaves, and if it arrives early (tasseling time) in places like the Deep South or even Midwest, a fungicide spray is crucial to save yield. Common rust (Puccinia sorghi) also occurs but is usually minor in impact.

Stalk and Ear Rots

Stalk rots are a group of diseases (e.g. Fusarium stalk rot, Anthracnose stalk rot, Diplodia stalk rot) that infect stalk tissue, often becoming evident after pollination. They cause pith to rot, weakening stalks and leading to lodging, especially if plants were stressed (dry conditions, high plant populations, or leaf disease that forced the plant to remobilize nutrients from stalk to grain). Managing stalk rots involves hybrid selection (some have better stalk strength and resistance), maintaining balanced fertility (adequate K), and harvesting in a timely manner if fields are at risk (to avoid lodging losses). Ear rots like Gibberella (red/pink mold) or Diplodia (white mold) can occur under wet conditions during silking to early grain fill; they can produce mycotoxins in grain (e.g. Gibberella can produce DON vomitoxin). Using resistant hybrids and crop rotation (to break disease cycles) helps reduce ear rots.

Other Pathogens and Integrated Management

Goss’s wilt (bacterial wilt) is another notable disease in some Corn Belt areas – a bacterial infection causing leaf necrosis; it’s managed by resistant hybrids and residue management (rotation, as the bacterium lives on corn debris). Stewart’s wilt (another bacterial disease) is vectored by corn flea beetles, now relatively rare. Nematodes (like root lesion or needle nematodes) can also feed on corn roots in sandy soils, but damage is sporadic and often goes undiagnosed; seed treatments for nematodes are available if needed. In summary, corn’s major pests and diseases are addressed through an integrated approach: selecting hybrids with appropriate resistance packages, using crop rotation to break pest cycles (especially for rootworms and many diseases), scouting and applying pesticides (fungicides/insecticides) only when economic thresholds are reached, and employing cultural practices like tillage or residue management to reduce inoculum. The result is that even though corn is grown on ~90 million acres in the US, average yields continue to improve as farmers successfully mitigate these biotic stresses.

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Seasonal Work Timeline

Pre-Season Planning and Preparation

Seasonal Work Timeline: A corn production year follows a structured calendar of operations:

Fall (post-harvest): After harvest, many farmers do primary tillage (chisel plow, disk ripper, etc.) to break up compaction and incorporate residue. This is also when soil sampling typically occurs (every 2–4 years) to assess fertility needs. Fall is often when lime is applied if needed, as it takes time to react with soil. In some regions, fall anhydrous ammonia application is common, putting down nitrogen for the next season’s corn when soils are cool enough to minimize N loss. Some farmers also do drainage maintenance in fall – fixing tile lines or cleaning ditches.

Early Spring Operations

Early Spring: As soon as fields are fit to enter (soil dried enough to support equipment), farmers begin seedbed preparation – often with a field cultivator, finishing disk, or soil finisher to create a level planting surface. This is also when many apply pre-plant fertilizer – broadcasting phosphorus and potassium, or applying nitrogen if not done in fall. Some farmers apply pre-emergence herbicides at this time.

Planting Season Activities

Planting Window: When soil temperatures reach about 50°F (10°C) at 2-inch depth and the weather forecast is favorable, corn planting begins. This is a critical and intense period – many farms run planters extended hours to complete planting in the optimal window (typically 2–3 weeks in May for much of the Corn Belt). During planting, farmers may apply starter fertilizer in-furrow or as a 2×2 band (2 inches to the side and 2 inches below the seed). Some also apply insecticides or in-furrow fungicides if conditions warrant.

Early-Season Management

Early Season (V1–V6): Once corn emerges, farmers scout for stand establishment – checking population and uniformity. This is when post-emergence herbicides are typically applied (around V2–V5) to control weeds. Many farmers also apply side-dress nitrogen during this window (around V4–V8), putting nitrogen near the developing root system when corn begins rapid uptake. Some may use aerial imagery or tissue testing to guide these applications.

Mid-Season Operations

Mid-Season (V7–VT): As corn grows rapidly, farmers monitor for insect pests and foliar diseases. In areas with high disease pressure, a fungicide application may occur around tasseling (VT) to protect the ear leaf and leaves above it. This is also when irrigation management becomes critical in irrigated regions – corn water use peaks around silking. Some farmers apply a late-season nitrogen application if needed, based on crop sensing or modeling.

Harvest Preparation and Operations

Late Season (R1–R6): After pollination, farmers monitor grain fill and watch for stalk rot or other issues that might affect harvestability. As corn approaches physiological maturity (R6, black layer), they begin preparing harvest equipment. When grain moisture drops to acceptable levels (typically 22–28% moisture), combining begins. This is followed by grain drying (if needed) to reduce moisture to safe storage levels (about 15%). Post-harvest, farmers make decisions about fall tillage and cover crops, and the cycle begins again.

Regional Variations

This seasonal sequence can vary slightly with geography – for instance, in the South (e.g. Mississippi Delta or Georgia), corn may be planted in March and harvested by August, while in the Northern Plains (North Dakota), planting in May and harvesting in late October is normal. But in all cases, timing each operation correctly is vital to achieve optimal corn yields with the resources invested.

Mechanization and Technology

Land Preparation and Tillage Equipment

Mechanization and Technology: Corn production in the U.S. is highly mechanized, relying on advanced farm machinery at every step. Land preparation is done with large tractors (often 200–400 horsepower) pulling plows, disks, or strip-till rigs. These tractors are usually equipped with GPS auto-steering, allowing precise parallel passes with minimal overlap. Tillage depth and implement settings can be adjusted on-the-go from the cab, and some systems record maps of tillage operations.

Modern Planting Systems

Planting is carried out by sophisticated planters that may span 40–60 feet. Modern planters have 16, 24, or even 36 rows, each with a row unit that opens a furrow, meters a seed, and firms it in soil. Seed metering is typically via vacuum or positive air pressure systems that singulate seeds accurately; many planters now feature electric drive row units for precise control and automatic shut-off on overlap areas (to avoid double planting headlands). Planters also often include sensors and monitors that report real-time data on seed spacing, population, and skips/doubles. Achieving uniform seed spacing and emergence is crucial – as research shows, uneven spacing or timing can reduce yield, so technology helps maintain consistency [32]. Some planters utilize variable-rate seeding technology which changes the seeding rate on different parts of the field (e.g. higher population in rich low ground, lower on hilltops) based on prescription maps.

Chemical Application Equipment

Chemical application is heavily mechanized as well. Large self-propelled sprayers (120+ ft booms) are used to apply herbicides, insecticides, and fungicides. These sprayers have computerized rate controllers and GPS-guided section control or even individual nozzle control, which automatically shut off sections of the boom in areas already treated (eliminating overlap and reducing chemical waste). Sprayers cover ground quickly (10–20 mph), allowing timely applications on large acreages. Fertilizer application is done with floater trucks or toolbars that precisely deliver nutrients; even manure is applied with equipment that uses flow meters and GPS mapping of rates.

Irrigation Systems

Irrigation in corn is mechanized through center pivot systems that can be a quarter-mile long, rolling on electric motors. These pivots can be fitted with GPS and controllers to do variable-rate irrigation or to apply fertigation (fertilizer through irrigation) uniformly.

Harvesting and Post-Harvest Technology

Harvesting is a pinnacle of mechanization: combines are massive machines that cut and thresh corn efficiently. A combine harvester for corn is fitted with a corn header (with snapping rolls for pulling stalks and stripping ears). Inside, a rotary or conventional threshing system shells the kernels from cobs. Combines have onboard computers that adjust threshing speed, fan speed, and sieve settings to minimize grain loss and trash. Most combines now come standard with yield monitors and GPS receivers, which log grain yield and moisture at a fine spatial resolution as the crop is harvested. In fact, yield monitors are used on a large portion of corn acreage (over 40% of U.S. corn acres were yield-mapped by late 2010s [33]). These yield maps are later used to make management decisions (like variable-rate fertilizer for the next year). Combines also utilize auto-steering and even header height control (sensors that keep the header at optimum height above ground). Harvest capacity is immense – a modern combine can harvest 200–300 bushels per minute in high-yield corn. To keep it moving, grain carts (large auger wagons) are used: a tractor drives alongside the moving combine to collect grain on-the-fly, then dumps into trucks at the field edge. This reduces combine downtime. Logistics and storage are also mechanized: many farms have high-capacity grain dryers, augers, and storage bins equipped with moisture sensors and aeration fans. Trucks haul corn from field to storage or elevator, often scheduled via software for efficiency. Supporting all this, maintenance tasks are eased by technology – for example, many tractors and combines come with telematics that send performance data and even enable remote diagnostics by dealers.

Precision Agriculture

GPS and Guidance Systems

Precision Agriculture: Corn production has been at the forefront of precision agriculture adoption. GPS guidance is now standard on most corn farms – tractors, sprayers, and combines use satellite positioning to steer accurately, reducing overlap and skips. This not only saves on inputs but also reduces operator fatigue. Auto-steer systems can maintain accuracy of +/- 1 inch using RTK (Real-Time Kinematic) correction signals. This enables practices like strip-tillage where fertilizer bands are placed in fall, and then planting occurs directly over these bands in spring.

Variable Rate Technology

Variable-rate technology (VRT) is widely used in corn. Based on soil sampling, yield history, or other data layers, farmers create prescription maps that tell equipment to vary inputs across the field. For example, variable-rate fertilizer applications might put more phosphorus on low-testing areas and less on high-testing zones. Variable-rate seeding adjusts corn population – perhaps 28,000 seeds/acre on poorer soils and 36,000 on better ground. The goal is to match inputs to the productive capacity of each part of the field, optimizing return on investment.

Sensing and Monitoring Systems

Sensing technology continues to advance. Soil sensors can measure moisture at multiple depths, helping irrigation decisions. Crop sensors mounted on equipment measure plant vigor – for instance, optical sensors detect greenness (NDVI) as a proxy for nitrogen status, enabling real-time variable-rate nitrogen application. Yield monitors on combines create detailed maps showing productivity variations across fields. These maps become valuable historical data layers for future decisions.

Data Management and Decision Support

Data management is a growing aspect of precision corn production. Farmers collect terabytes of data from equipment, weather stations, soil tests, and imagery. Farm management software helps organize this information and extract insights. Some systems can automatically generate variable-rate prescriptions based on multiple data layers. Wireless data transfer allows information to move seamlessly from field equipment to office computers or cloud storage.

Remote Sensing and Imagery

Remote sensing via satellites, airplanes, or drones provides another data stream. Satellite imagery can track crop development across the season. Drone scouting with high-resolution cameras or multispectral sensors can identify problem areas (nutrient deficiencies, pest hotspots, drainage issues) before they’re visible to the naked eye. Some farmers use thermal imagery to detect moisture stress.

Precision Irrigation and Weather Monitoring

Precision irrigation in corn uses soil moisture probes, evapotranspiration models, and weather forecasts to optimize water application. Modern pivots can vary water rates across the field based on soil type or topography. Weather stations on farms provide hyperlocal data for spray timing and irrigation scheduling. Some systems integrate weather forecasts with crop models to predict disease risk or growth stage.

Future Trends and Automation

Looking ahead, robotics and automation are entering corn production. Autonomous tractors are being tested that can perform fieldwork without an operator. Machine learning algorithms analyze the growing body of farm data to find patterns and make recommendations. Predictive analytics help forecast yield potential or pest outbreaks based on current conditions and historical patterns. The integration of these precision technologies continues to make corn production more efficient, sustainable, and profitable – allowing farmers to apply the right input, at the right rate, in the right place, at the right time.

Drone Applications in Corn

Corn Growth Stages and Timing

Corn development is divided into vegetative (V) stages and reproductive (R) stages, starting with emergence (VE) and ending at physiological maturity (R6). The vegetative phase begins with emergence (VE), typically 5-10 days after planting, and progresses through leaf stages (V1 to VT) until tasseling (VT), which occurs around 45-55 days after planting. The reproductive phase starts with silking (R1) at 45-55 days, followed by kernel development stages: blister (R2) at 55-69 days, milk (R3) at 63-77 days, dough (R4) at 69-83 days, dent (R5) at 80-97 days, and physiological maturity (R6) at 100-120 days after planting. A typical corn hybrid requires about 100-120 days from planting to maturity, though this can vary based on environmental conditions.

Assuming a planting date of May 1st in the Corn Belt, the timeline aligns as follows:

  • VE: May 6-10
  • V1: May 15-20
  • V6: June 1-5
  • VT: July 1-5
  • R1: July 5-10
  • R2: July 15-20
  • R3: July 25-30
  • R4: August 5-10
  • R5: August 15-20
  • R6: September 5-10
  • Harvest: Late September to early October

Drone Applications by Growth Stage

Drones, like the DJI Mavic 3 Multispectral with 20 MP RGB sensor and 5 MP multispectral sensor including Green (560 ± 16 nm), Red (650 ± 16 nm), Red Edge (730 ± 16 nm), and Near Infrared (NIR, 860 ± 26 nm), can be utilized for various tasks at different growth stages, enhancing precision agriculture practices. Below, we detail the applications, their timing, suitable drone type (RGB or multispectral), and applicable vegetation indices such as NDVI, EVI, GNDVI, NDRE, and CVI where relevant.

Pre-Planting to VE (Before May 6)

  • Application: Field preparation assessment, including soil moisture, residue cover, field boundary mapping, obstacle identification, stone mapping, and high-resolution digital surface acquisition.
  • Details: Visual inspection aids in ensuring optimal planting conditions, while RTK-equipped drones generate precise elevation models for water management tasks such as field leveling, grading, and drainage planning. Stone mapping helps identify removal needs before planting.
  • Suitable Drone Type: RGB for visual inspection; RTK-equipped drones with LiDAR or photogrammetry capabilities for high-precision elevation mapping (1-3 cm vertical accuracy).
  • Timing: 2-4 weeks before planting, allowing time for field modifications if needed.
  • Vegetation Index: None applicable for bare soil mapping; however, digital elevation models and contour maps are generated for drainage planning.

VE (Emergence, May 6-10)

  • Application: Emergence counting, to ensure a uniform stand and identify gaps or poor emergence areas.
  • Details: Multispectral drones are preferred, using NDVI (range: 0.3-0.5, higher values indicate healthy emergence) to detect small green plants against soil background, though RGB can be used if plants are visible. This is crucial for early yield potential assessment.
  • Suitable Drone Type: Multispectral (preferred), RGB.
  • Timing: 5-10 days after planting.
  • Vegetation Index: NDVI (Normalized Difference Vegetation Index) - Measures plant health and biomass, aiding in assessing stand establishment.

V1 to V5 (Early Vegetative, May 15 to late June)

  • Applications:
    • Weed Detection: Multispectral drones identify weeds based on spectral signatures using NDVI (range: 0.3-0.5, weeds may show distinct values from corn), crucial before canopy closure (around V4-V5) to plan targeted herbicide applications. Research shows drones can map weed patches efficiently, reducing chemical use.
    • Plant Stand Assessment: Both RGB and multispectral drones count plants to assess uniformity, using NDVI (range: 0.3-0.5, higher values indicate uniform growth) to ensure optimal growth conditions.
    • Nitrogen Status Assessment: Multispectral drones measure GNDVI (range: 0.5-0.8, higher values suggest adequate nitrogen) and NDRE (range: 0.5-0.7, indicating sufficient nitrogen) to assess early-season plant health, guiding fertilizer decisions.
  • Suitable Drone Type: Multispectral for weed detection and nitrogen status; RGB or multispectral for plant stand assessment.
  • Timing: 10-30 days after planting, aligning with early weed competition and rapid growth.
  • Vegetation Indices:
    • NDVI - Monitors early growth and weed presence.
    • GNDVI (Green Normalized Difference Vegetation Index) - Assesses chlorophyll content for nitrogen status.
    • NDRE (Normalized Difference Red Edge) - Evaluates nitrogen levels for fertilizer planning.

V6 to VT (Late Vegetative to Tasseling, June 1 to July 5)

  • Applications:
    • Nitrogen Status Assessment: Multispectral drones assess NDRE (range: 0.5-0.7, higher values indicate sufficient nitrogen) and GNDVI (range: 0.5-0.8, suggesting healthy chlorophyll) for side-dress fertilizer decisions, aligning with peak nitrogen uptake around V8 to VT.
    • Water Stress Detection: Multispectral or thermal drones detect water stress, using NDVI (range: 0.5-0.8, lower values may indicate stress) and EVI (range: 0.4-0.8, stable in dense canopies), important as the plant enters rapid growth and before flowering, to prevent yield impacts.
    • Disease Detection: Multispectral drones spot early signs of foliar diseases like Gray Leaf Spot using CVI (range: 1-3, lower values suggest disease or deficiency), enabling timely fungicide applications.
  • Suitable Drone Type: Multispectral for nitrogen and disease; Multispectral or thermal for water stress.
  • Timing: 30-55 days after planting, critical for management decisions during rapid growth.
  • Vegetation Indices:
    • NDRE - Key for nitrogen management.
    • GNDVI - Monitors chlorophyll and nitrogen status.
    • NDVI - General health and stress detection.
    • EVI (Enhanced Vegetation Index) - Assesses canopy health in dense growth.
    • CVI (Chlorophyll Vegetation Index) - Identifies chlorophyll issues related to disease.

VT to R1 (Tasseling to Silking, July 1-10)

  • Applications:
    • Water Stress Detection: Critical during flowering, multispectral or thermal drones monitor for water stress using NDVI (range: 0.7-0.9, lower values indicate stress) and EVI (range: 0.4-0.8, reliable in dense canopies) to prevent kernel abortion, a major yield determinant.
    • Disease Detection: Multispectral drones continue monitoring for diseases using CVI (range: 1-3, lower values suggest disease impact), protecting the ear leaf and above during pollination.
    • Pollination Monitoring: RGB drones visually inspect tassel and silk emergence, though less common, for uniform pollination assessment.
  • Suitable Drone Type: Multispectral or thermal for water stress; Multispectral for disease; RGB for pollination.
  • Timing: 55-60 days after planting, a sensitive period for yield.
  • Vegetation Indices:
    • NDVI - Monitors overall plant health during critical flowering.
    • EVI - Ensures accurate health assessment in dense canopies.
    • CVI - Detects disease-related chlorophyll reduction.

R1 to R4 (Silking to Dough, July 5 to August 10)

  • Applications:
    • Yield Prediction: Multispectral drones estimate biomass and predict yield using NDVI (range: 0.7-0.9, higher values correlate with higher yield), best between R1 and R4, as kernel number and size are set.
    • Disease Detection: Multispectral drones monitor for foliar diseases affecting grain fill using CVI (range: 1-3, lower values indicate disease).
    • Stalk Strength Assessment: RGB drones check for lodging, indicating potential stalk rot or weakness.
  • Suitable Drone Type: Multispectral for yield prediction and disease; RGB for stalk strength.
  • Timing: 60-90 days after planting, during kernel development.
  • Vegetation Indices:
    • NDVI - Predicts yield based on biomass.
    • CVI - Monitors chlorophyll for disease impact on grain fill.

R5 to R6 (Dent to Physiological Maturity, August 15 to September 10)

  • Applications:
    • Stalk Strength Assessment: RGB drones assess for lodging, ensuring harvest readiness as stalks may weaken.
    • Disease Detection: Multispectral drones monitor late-season diseases using CVI (range: 1-3, lower values suggest late-season issues), protecting final grain weight.
  • Suitable Drone Type: RGB for stalk strength; Multispectral for disease.
  • Timing: 90-120 days after planting, as the crop approaches maturity.
  • Vegetation Index:
    • CVI - Assesses late-season health and disease impact.

Post-R6 to Harvest (After September 10)

  • Application: None primary, though RGB drones can assess moisture drying progress visually, though less reliable compared to ground methods.
  • Suitable Drone Type: Not applicable for primary use.
  • Timing: Post-physiological maturity, focusing on harvest logistics.
  • Vegetation Index: None applicable.

Anytime Applications

  • Water Logging Detection: RGB drones identify standing water after heavy rains, preventing root damage at any growth stage.
  • Damage Assessment: Both RGB and multispectral drones assess storm, pest, or disease damage using NDVI (range varies, lower values indicate damage), supporting insurance claims and management decisions.
  • Timing: As needed, particularly after adverse weather events.
  • Vegetation Index:
    • NDVI - Detects damage extent through reduced plant health.

Crop Growth Season Calendar

To provide a practical guide, we align drone applications with a calendar based on a May 1st planting date in the Corn Belt, incorporating vegetation indices where applicable:

Month Week Growth Stage Drone Applications Suitable Drone Type Vegetation Indices Used
May 1-2 Pre-planting to VE Field preparation assessment RGB None
3 VE Emergence counting Multispectral (preferred), RGB NDVI (0.3-0.5)
4 V1 to V2 Weed detection, Plant stand assessment, Nitrogen status assessment Multispectral for weed and nitrogen; RGB or multispectral for stand NDVI (0.3-0.5), GNDVI (0.5-0.8), NDRE (0.5-0.7)
June 1-2 V3 to V5 Same as above Same as above NDVI (0.3-0.5), GNDVI (0.5-0.8), NDRE (0.5-0.7)
3-4 V6 to V8 Nitrogen status assessment, Water stress detection, Disease detection Multispectral for nitrogen and disease; Multispectral or thermal for water NDRE (0.5-0.7), GNDVI (0.5-0.8), NDVI (0.5-0.8), EVI (0.4-0.8), CVI (1-3)
July 1-2 V9 to VT, VT to R1 Water stress detection, Disease detection, Pollination monitoring Multispectral or thermal for water; Multispectral for disease; RGB for pollination NDVI (0.7-0.9), EVI (0.4-0.8), CVI (1-3)
3-4 R1 to R2 Yield prediction, Disease detection, Stalk strength assessment Multispectral for yield and disease; RGB for stalk NDVI (0.7-0.9), CVI (1-3)
August 1-2 R2 to R4 Same as above Same as above NDVI (0.7-0.9), CVI (1-3)
3-4 R5 to R6 Stalk strength assessment, Disease detection RGB for stalk; Multispectral for disease CVI (1-3)
September 1-2 R6 to harvest None - None
Any time As needed - Water logging detection, Damage assessment RGB for water logging; RGB or multispectral for damage NDVI (varies)

This calendar provides farmers with a structured approach to leverage drone technology, particularly the DJI Mavic 3 Multispectral, enhancing decision-making and optimizing corn production through the use of vegetation indices like NDVI, EVI, GNDVI, NDRE, and CVI.

Detailed Explanation of Vegetation Indices

The following vegetation indices are calculated using the DJI Mavic 3 Multispectral’s spectral bands, each with specific value ranges and interpretations for corn management:

NDVI (Normalized Difference Vegetation Index)

  • Formula: (NIR - Red) / (NIR + Red)
  • Value Range for Corn: Early growth (V1-V3): 0.3-0.5; Rapid growth (V6-VT): 0.5-0.8; Peak growth (VT-R1): 0.7-0.9
  • Interpretation: Higher values indicate healthier plants with more biomass. During early stages, increasing NDVI suggests good growth; during reproductive stages, it correlates with higher yield potential. Lower values may indicate stress from water, nutrients, or pests, requiring further investigation. Widely used for general corn health assessment and yield prediction.

EVI (Enhanced Vegetation Index)

  • Formula: 2.5 * (NIR - Red) / (NIR + 6Red - 7.5Blue + 1)
  • Value Range for Corn: Healthy canopy: 0.4-0.8
  • Interpretation: Similar to NDVI but better for dense canopies where NDVI might saturate. Higher EVI values indicate denser, healthier canopies, making it advantageous in no-till or high-residue corn fields with variable soil conditions, providing a more accurate measure of canopy vigor during rapid growth phases.

GNDVI (Green Normalized Difference Vegetation Index)

  • Formula: (NIR - Green) / (NIR + Green)
  • Value Range for Corn: Healthy corn: 0.5-0.8
  • Interpretation: Higher values indicate higher chlorophyll content, suggesting adequate nitrogen, particularly useful for monitoring nitrogen status in early vegetative stages to guide side-dress applications. Lower values may indicate nitrogen deficiency, impacting corn yield.

NDRE (Normalized Difference Red Edge)

  • Formula: (NIR - Red Edge) / (NIR + Red Edge)
  • Value Range for Corn: Adequate nitrogen: 0.5-0.7
  • Interpretation: Higher NDRE values indicate higher chlorophyll and likely sufficient nitrogen, crucial for nitrogen management during V6 to VT stages when corn has high nitrogen demand. Lower values suggest potential deficiency, guiding side-dress fertilizer decisions to optimize yield and reduce waste.

CVI (Chlorophyll Vegetation Index)

  • Formula: (NIR / Red Edge) - 1
  • Value Range for Corn: Healthy corn: 1-3
  • Interpretation: Higher values indicate more chlorophyll, suggesting healthy plants. Lower values may indicate stress or disease, impacting grain fill and yield, useful for identifying areas needing nutrient management or disease control during mid-season.

These indices, when combined with field observations, provide a robust framework for monitoring corn health, guiding management decisions, and optimizing yield throughout the growing season. Additional indices like SAVI, OSAVI, SR, MCARI, TVI, GCI, and a Green-based NDWI are calculable but are less commonly used for corn-specific applications with this drone due to specific needs or limitations (e.g., lack of SWIR for accurate water stress detection). For detailed formulas and broader applications, refer to studies like those from USDA ARS Vegetation Indices Definitions and Precision Ag Drones in Agriculture.

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Literature

Corn Growth and Development

  • Visual Guide to Corn Growth Stages | Land-Grant Press
    URL: Visual Guide to Corn Growth Stages | Land-Grant Press
    Provides a visual overview of corn growth stages from emergence (VE) through reproductive stages (R1–R6).

  • Corn Growth Stages | Integrated Crop Management (Iowa State Extension)
    URL: Corn Growth Stages | Integrated Crop Management
    Details the vegetative (V) and reproductive (R) stages, including timing (e.g., silking, pollination, kernel development) and management implications.

  • Corn Water Use | Pioneer® Seeds
    URL: Corn Water Use | Pioneer® Seeds
    Explains corn’s water requirements, especially highlighting stress around flowering (VT/R1) and impacts on yield during grain fill.

  • Western Wildfire Effects on Corn Crops | Crop Science US (Bayer Crop Science)
    URL: Western Wildfire Effects on Corn Crops | Crop Science US
    Discusses environmental stresses (such as wildfire-induced stress) during key growth stages (e.g., R5) that can affect yield.

Field Management and Tillage

Planting and Population Management

Nutrient and Fertilizer Management

  • Nutrient Removal Rates by Grain Crops | CANR.MSU.EDU
    URL: Nutrient removal rates by grain crops - Wheat
    Offers data on the nutrient uptake and removal of corn, which informs fertilization practices.

  • Fertilizing Corn | CSU Extension (Colorado State University)
    URL: Fertilizing Corn - 0.538 - Extension
    Provides guidance on fertilizer management for corn, particularly nitrogen application based on soil tests.

  • What is the Perfect Nitrogen Rate for Corn? | Purdue University Extension
    URL: What is the Perfect Nitrogen Rate for Corn?
    Discusses historical and modern recommendations for nitrogen rates in corn production, including crop rotation considerations (e.g., corn after soybean).

Pest and Weed Management

Crop Rotation and Specialized Management

Water Management and Irrigation

Precision Agriculture and Technology

Drone Applications and Remote Sensing

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