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Corn

Corn (Zea Mays) originates in the Andean region of Central America. It is one of the most important cereals both for human and animal consumption and is grown for grain and forage. In terms of global production, corn is the third most important food crop after rice and wheat. Demand for Corn is growing as both a fresh and processed food. Decreasing availability of land for area expansion means that yields will have to be improved. Critical to achieving improved yields will be access to an adequate water supply, including more efficient use of all available water. Present world production is about 786 million tons of grain corn from 158 million ha. The USA, China and Brazil are the world's major corn producing countries, accounting for nearly 62% of the total world production. Top four exporting countries are USA, EU, South Africa & Argentina. Corn is an important candidate crop for ethanol production with a yield of 3 to 4 m3/ hectare.

Corn is grown in climates ranging from temperate to tropic during the period when mean daily temperatures are above 15 °C and frost-free while the base temperature is 10ºC. The crop is sensitive to low temperature and frost. Optimum temperature for germination is 18 – 20 ºC. Delayed germination causes seed rot and reduced plant population. Heavy rains and water logging during pollination affects grain yield significantly. Proper rotation in corn system checks weeds, diseases, pests and avoids yield losses (2 – 19%) due to stalk rot disease. Dry beans, soybean and potatoes are the best rotational crops for disease management. Adaptability of varieties in different climates varies widely. Successful cultivation markedly depends on the right choice of varieties so that the length of growing period of the crop matches the length of the growing season and the purpose for which the crop is to be grown.

Corn is grown on a wide range of soils but the following soils are preferred: Medium and heavy textured, deep, well drained, fertile clay and silty loamy soils with good water holding characteristics. Acid or dense subsoils limit root penetration. The pH range of 7.0 to 8.5 is regarded as optimum. Corn is moderately sensitive to salinity. The crop is tolerant to soil salinity. The optimum plant density varies between 70,000 to 80,000 plants/ ha.

Adoption of drip irrigation and fertigation in corn proved to be technically feasible and economically viable and beneficial in many ways in several countries of the world. Drip irrigation in many diverse agro-ecological situations registered higher yield (12 – 14 tons/ ha) besides saving in water (less water by as much as 35 to 55% when compared to furrow and sprinkler irrigation), better grain quality, low labor costs (in comparison to conventional furrow irrigation), precise application of fertilizer, low operating pressures (in comparison to centre pivot sprinkler irrigation method). No water is wasted to evaporation, runoff, wind drift.

For high yields, the seasonal crop water requirements for corn were estimated to be 350 to 800 mm/ ha under a range of climatic conditions and varying length of growing season (90 – 150 days) with a daily evapotranspiration rate of 6 to 7.5 mm/ day. Irrigation scheduling using leaf water potential measurements by pressure chamber enabled efficient use of water, fertilizer and energy inputs. Corn is a heavy feeder of nutrients. The aim of the fertigation program is to cover the difference between crop demand and supply. Other best management practices include irrigation scheduling, protection of crop from pests and diseases, need-based weed management, timely harvesting and post harvesting operations to minimize yield losses.

Corn Best Practices

Best Management Practices (BMPs) are the best recommended agronomic practices for growing a specified crop. These practices are based on research and experience and apply to corn under the specified agro-ecological conditions.
The recommended BMPs are not the only way to grow corn but are the best way determined by Netafim. The BMPs may change as additional proven research becomes available.

Agro-ecological situation
Climate
Conditions: Temperate, tropical and subtropical
Climatic requirement: Crop of warm climate and adequate moisture; the crop is sensitive to low temperature and frost
Radiation: 500 – 600 cal/ cm2/ day
Growing degree days: 2700 for 130 days crop
Rainfall: 600 to 800 mm/ annum
Relative humidity: 50 to 80%
Base temperature: 10 ºC
Optimum temperatures: for germination 18 – 20 ºC; for growth, daytime, 25 – 33 ºC and night time 17 – 23 ºC.
Comment: Delayed germination causes seed rot and reduced plant population. Heavy rains and water logging during pollination affects grain yield significantly.

Soil
Soil suitability: Fertile, deep, well drained clay loam to silty loam soils with good water holding characteristics
Soil pH: 7.0 to 8.5
Soil critical nutrient levels: 15 – 18 ppm NO3–N, 16 – 21 ppm P, 121 – 160 ppm K, 101 ppm Mg, 076 – 1.0 ppm Zn
Soil bulk density: 1.3 – 1.4 Mg/m3 - better favors root penetration, proliferation and soil water air relations
Groundwater table: Below 2.0 m
Critical soil salinity level (ECe): 1.7 dS/m above which yield decreases
Solis to avoid: waterlogged soils

Crop rotation
Proper rotation in corn system checks weeds, diseases & pests and avoids yield losses.
Without proper rotation, yield losses are 2 – 19% due to stalk rot disease.
Dry beans, soybean and potatoes are the best rotational crops for disease management.

Improved varieties
Along with yield potential maturity is of primary importance in selecting a variety and hybrid that will produce mature, high test weight grain during a normal growing season for a particular area.
Several hybrids are available for all types of corn and include double crosses, three-way crosses, single crosses, and modified crosses (or sister line crosses) depending on the country.

Planting material
Seed

Spacing
Row spacing: 0.70 m to 0.90 m
Plant spacing: 0.2 m
Optimum plant density: Varies between 70,000 to 80,000 plants/ ha

Seeding rate
Varies with cultivar, planting date, seed size and cost of production
Generally 20 to 25 kg/ha
Seeding by dibbling or by mechanical planters

Land prepartion
Clod free seedbed with good tilth to express its grain yield potential, subsurface drip irrigation (SDI) installation and optimal soil water air relations.
Destroy the hard pan if any using either chisel plough or a sub soiler to a depth of 35 – 40 cm.
Primary tillage by mould board plough or disc plough and secondary tillage by disc harrows, tyned harrows or rotavator to achieve proper tilth. 
Compost: 15 – 20 tons/ ha

Planting for better stand, yield and quality
Poor plant stand registers low yield
Soil temperature at planting: 15 – 18 °C
Planting depth: 3 to 5 cm under adequate soil moisture

Weed control
Managing weeds is critical for successful corn production.
Weeds compete for light, water, nutrients, etc., and reduce grain yields by 45% in Germany, 30% in Russia, 50% in India, 41 to 86% in USA and 40% in Indonesia, depending on the weed intensity.
Critical crop – weed competition period is initial 7 – 8 weeks.
Integrated weed control program involving crop rotation, manual weeding, good seedbed preparation, maintenance of optimum plant population, mechanical inter cultivation and herbicide chemical applications.

Herbicides per hectare:
Before planting & at planting
Alachlor 2.8 – 3.4 kg
Atrazine 1.8 – 2.3 kg
Glyphosate 1.15 – 4.5 kg
After planting
Pendimethalin 0.95 – 1.9 kg
Glyphosate 1.15 – 4.5 kg
2, 4-D amine 0.26 – 0.52 kg
Paraquat 0.28 – 0.56 kg
Metribizin 0.085 – 0.170 kg

Irrigation system
Drip version: Surface or subsurface drip irrigation combined with fertigation.
Drip product: DripNet PC, Tiran, Dripline 17009, Super typhoon, UniRam and Python 22135.
Drip Line spacing: 1.4 to 1.9 m with 1 lateral for every 2 crop rows
Emitter spacing: 0.4 m to 0.75 m - depending on soil texture
Emitter flow rate: 0.6 LPH, 1.0 LPH, 1.6 LPH and 2.0 LPH - depending on soil texture

Crop water requirement & irrigation scheduling
Estimate crop water requirements as a product of daily reference crop evapotranspiration (ETo) by Penman-Monteith method and crop coefficient for a given day according to the plant developmental stages.
Begin with 0.3 Kc of daily ETo in the initial period, raise it to 0.8 to 0.9 at vegetative stage, 1.2 at tasseling, silking & pollination stages, and decrease it to 0.5 at maturity of corn.
Irrigation scheduling using leaf water potential measurement by pressure chamber at 1.4 to 2.0 MPa at different stages enabled efficient use of water, fertilizer & energy inputs.
Daily crop water requirement: 6 to 7.5 mm/day
Seasonal crop water requirement: 350 to 800 mm - under range of environments

Fertigation
Apply mineral fertilizers based on the targeted yield, leaf analysis results, fertilizer experiment results, leaf deficiency symptoms, nutrient uptake, soil analysis results, nutrient recycling, etc.

Nutrient uptake:
191 kg N
89 kg P2O5
235 kg K2O
73 kg Mg
57 kg Ca
21 kg S for a yield of 9.5 tons/ha

Recommended nutrient dose: 120 to 180 kg N + 45 to 80 kg P2O5 + 30 to 80 K2O kg/ha
Critical levels in plant dry matter: 2.9% N, 0.25% P, 1.9% K, 0.15% Mg, 0.4% Ca, 0.15% S, 15 ppm Zn, 25 ppm Fe, 15 ppm Mn, 5 ppm Cu & 10 ppm B
For fertigation use water soluble fertilizers such as urea (46% N), potassium nitrate (13% N & 46% K2O), monoammonium phosphate (12% N & 61% P2O5) and ammonium nitrate (34% N).

Pests & diseases
Important pests: Flea beetles, seed corn maggots, leaf minor, spider mites, white grub, wire worm, cut worms, leaf aphids, army worm, stalk borer, root worm and European corn borer
Important diseases: Seedling blight, corn leaf blight, bacterial leaf blight, anthracnose leaf blight, maize dwarf mosaic, common rust, common smut, ear rot, kernel rot and grey leaf spot
Detect outbreaks and identify problem areas by routine patrols.
Monitor economic threshold levels and take up appropriate plant protection measures.

Harvesting
Corn is mature when the grain has about 30 – 32% moisture.
The best time to harvest depends on your harvest and storage system.
Timely harvesting of grain corn minimizes lodging, less ear drop page, avoids water logging and harvesting losses.

Grain yield
Under drip irrigation and fertigation a good commercial grain corn yield is 10 – 12 tons/ ha depending on length of growing season and variety (10 to 13 percent moisture).
Water utilization efficiency: Varying between 1.6 and 2.0 kg/m3

FAQ'S

Should I plant Bt corn?
Bt corn effectively controls both Southwestern and European corn borers and has moderate control on corn ear-worms and fall army worms. However, Bt corn does not control the primary insect pests during stand establishment such as chinch bugs, cutworms, root worms & wire worms. Thus, using a Bt hybrid will not substitute for the use of a soil applied insecticide at planting. Research data suggest the inclusion of a Bt event does not always increase hybrid yield potential compared to conventional premium hybrids. A grower would not likely recover the higher seed cost of the Bt technology unless a corn borer infestation significantly reduces the yield level of conventional hybrids. Typically, the Bt technology seed expense is about $ 10 higher per acre when compared with a conventional premium hybrid. Unfortunately, seasonal corn borer populations are not very predictable. Thus, local historical infestation levels should be used to justify Bt hybrid utilization. Bt hybrids should be used as insurance against a severe corn borer outbreak in areas that traditionally have corn borer populations.
How deep should I plant corn seed?
Many producers unfamiliar with corn seedling development plant corn too shallow. Corn seed should be planted 4 – 5 cm deep, depending upon soil moisture and soil texture. For example, corn seed should be planted about 4 cm deep on moist, clay soils or conversely and about 5 cm deep on dry, sandy soils. Planting depth should be set in the field during planting - not necessarily in the shop, based upon the owner's manual. This is important because soil type, seedbed condition and moisture may influence actual depth. Corn seed's inherent energy and germination process ensure emergence from depths as great as 7.5 cm. Shallow planting often leads to root development problems. The origination point of the nodal root system is moved upward when corn seed is not planted deep enough. Corn seed placed less than 2.5 cm deep will develop nodal roots at or above the soil surface. This exposes these roots to factors such as hot, dry soil, herbicide injury, and insect predation, which can significantly impede root development. This will likely to lead to early season problems with plant stand/ unit area and nutrient deficiencies. Furthermore, birds may also reduce stand by extracting shallow-planted corn seeds.
Should I use subsurface or surface drip system?
Subsurface drip irrigation in corn has shown to have many agro technical advantages such as higher yield and improved grain quality, besides saving in water (35 to 55% when compared to furrow & sprinkler irrigation), low labor costs (in comparison to conventional furrow irrigation), precise application of fertilizer, low operating pressures (in comparison to centre pivot sprinkler irrigation method). Furthermore, the drip lines are protected from agro-machinery damage. The actions of agro machinery such as spraying of plant protection chemicals and mechanical harvesting do not interfere with the day to day irrigation system protocols. Furthermore, no-till farming becomes a reality. No water is wasted to evaporation, runoff, wind drift or deep percolation, and uniformity is generally greater than 90%.
When should irrigation of corn be terminated?
Irrigation should be continued long enough to supply plant moisture needs until physiological maturity is reached. Physiological maturity is signified by the formation of a dark abscission layer, referred to as the "Black Layer" at the base of kernels. This abscission layer cuts off water and dry matter transfer into the kernel. Kernels usually have a moisture content of 28 – 35% at this stage. This abscission layer forms when hard starch accumulation completes its progression from the top to bottom of a kernel. Seed weight accumulation is complete at this time. Physiological maturity usually occurs about 20 days after dent stage or 60 days after silking. A common problem is early termination of irrigation. Premature irrigation termination will accelerate maturity, prohibiting kernels from reaching their full potential size and weight. Although kernels appear somewhat mature and corn water use begins declining at the dent stage, this is too early to terminate irrigation. Potential kernel weight is only about 75% complete at the dent stage. Thus, termination of irrigation at the dent stage can reduce grain yields as much as 15-20% when hot, dry conditions persist.
How much a drip irrigation system costs per hectare of corn?
This is very variable and depends on the following factors: 1. Conveyance of water from source to the field – normally this is the most expensive component of the irrigation system. It depends on the distance and elevation the water has to be conveyed by the pipelines. 2. Peak crop water demand – Amount of water we need to apply to meet the peak crop evapotranspiration requirements during the corn crop peak demand. This is a function of prevailing climate conditions, crop canopy cover and efficiency of the irrigation system. 3. Other considerations: The land topography (flat or undulated) of the design area; the soil texture which determines the emitter spacing, for example sandy soils require closer emitter spacing and clayey soil require wider emitter spacing that will have a significant impact on the system cost per unit area.
What is the life of the drip system and after how many years I have to renew it?
The accumulated field experience revealed that corn raised under subsurface drip irrigation system can continue up to ten and/ or more years before the field is renewed. During the renewal of a drip system all the hydraulics (pipes, pump filters, etc.) remain intact in the field for further use and only the drip line must be replaced which represents around 35 – 40% of the total system cost per unit area.

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