Corn

Crop rotation - Crop development

Why is it important?

• Crop rotation, as a rule, improves performances of each crop, though corn is one of most resilient crops at this regard and can be cropped for many years on the same field.
• Rotation, anyway, allows to spread operations in different seasons of year which eases management of farms.
• Exploitation of soil fertility is improved, as different crops roots explore different layers of soil: also different crops use different fertilizers at different rates.
• Structure of soils improves, because residues from crop roots stay at different depths and residues are also different.
• Management of pests, diseases and weeds get easier because different crops have different pests and different chemicals are applied.
• Corn yield increases when corn and soybean are grown in sequence instead of continuously. One factor is the effect of residue on nitrogen (N) supply. Soybean residue is lower in quantity than corn residue, and it has a much higher N content. The breakdown of soybean residue, therefore, ties up little or no N, leaving more for the following corn crop.
• Corn is one of most resilient plant to continuous monoculture, especially in fertile light soils and when residue are incorporated into soil with abundant fertilization, thus improving the organic matter content of soil. Tests have shown the possibility of cropping mais on the same fields for 50 years. In monoculture, tillage management must be particularly careful, avoiding compaction of soil. However, corn in rotation with soybean or other legumes is surely a best choice on order to perform a better weed and pests’ control and using less N on maize. Other cereals can entry rotation, as wheat and barley, as well as row crops as sugarbeet, sunflower and others.

Tillage

• Primary tillage for corn is better carried out at fall.
- Research discovered that reducing both clod and valley sizes in the fall can dramatically reduce the risk of emergence problems in spring.
- Ideal Clod Size:
Prairie Soils: 15 cm (6 in) or less
Forest Soils: 12 cm (4.5 in) or less
- Action of frost on tilled soil during the winter helps in reaching a proper seed bed texture in spring.
• Timeframe: Primary tillage should begin behind the combine.
• A wide array of tools are available for primary tillage, such as
- Moldboard plow
- Chisel plows
- Disk rippers
- Offset disk.
• Disk rippers can be used for aggressive residue handling up front, more clearance, and an array of seedbed attachments on the back. This reduces field leveling and moisture losses in spring when soils are recharged with water.
• Secondary tillage is carried out before planting in spring. The goal is to achieve a proper seedbed, which means soil particles of right size for good contact between seeds and soil.
• Soil with a rough surface hinders proper seed germination and plant growth, ultimately leading to lost potential yield.
• A good seed bed is important, because plant roots require water and oxygen from the soil roots pore space for sprouting.
• The right soil-air-water balance helps in limiting plant stress during drought periods and enables the plant to fully explore the soil profile for nutrients. Plants are able to use water efficiently and grow strong roots for good anchorage.
• Research carried out showed that many as 7000 plants per hectare, or up to 10 percent of the net effective stand, could be lost due to poor seed bed conditions. Most of those lost plants were recovered, simply by focusing on delivering level output, both clod and valley free, following primary tillage.
• In APAC Region, ploughing (moulboard plough) is still very common as primary tillage for corn. On average, working depth is between 28 and 35 centimetres. Nevertheless, more and more customers are realizing that disk rippers are an outstanding alternative to moulboard plough. Disk rippers allows for good soil structure, consistent soil tilth, sufficient residue management and seedbed finishing in one pass, with evident economic advantages when compared with ploughing. More, existing hard pans are broken, with advantages for root growth, plant nutrition and water management.
• Seedbed finishing is performed with an array of implements, as tine harrows, disk harrows, rototills and many others. The goal is to get a firm seedbed beneath a layer of loose soil on surface, allowing for uniform and quick germination of seeds. If the upper layer is too fine, crusting may happens.

Planting

Uniformity is everything

• Uniformity in corn emergence is an extremely important factor for high yields which require having enough productive plants to utilize available resources. And productive plants require a wellprepared seed bed.
• Plants that emerge uniformly and progress at the same rate of development throughout the growing season, also known as “photocopy plants,” deliver improved yield potential. Two bad plants will not give as one good.
• Uneven emergence introduces inefficiencies and adds competition within the stand. Larger, early emerging plants obtain a greater proportion of available resources (light, water, nutrients) than smaller, later-emerging plants.
• Purdue University research says that uneven emergence can reduce corn yields by 9 to 22 percent. Significant plant spacing variability is also detrimental and can reduce corn yields from 2 to 4 percent.

Spraying

• In modern corn cultivation, crop protection is of paramount importance, whatever the crop pattern are: and the less tillage is applied, the more chemical control of weeds gets crucial.
• Weed control is carried out both with pre-planting, pre-emergence and on top spraying. Weeds or and pest can damage the yield up to the 100%, if not controlled or controlled to late.
• Pest control (e.g. European corn borer) is often needed by top spraying on high plants.
• When spraying is needed, timeliness is more crucial than in other operations. Weeds and pests are to be hit in right time and with precise doses of chemicals.

Hoeing

A good hoeing improves water utilization

• Hoeing, manual or mechanical, was a must when herbicides were not available.
• Today it is more a complementary operation, helping weed control and water management in dry soil.
• To be carried out when corn is about 10-20 centimeters high, to avoid mechanical damages to the crop.

Harvesting

• Corn is ripe when kernel moisture content is about 30%.
• Harvest when kernels grains contain 25% moisture or, better, less than that figure.
• It occurs from end August to October-November.
• Corn header is a dedicated tool and can be equipped with stalk chopper.
• Kernel moisture is about 30 percent at R6. Then, drying rates are normally 0.4 to 0.8 percent moisture per day. Ideal harvest moisture for field corn is 15 to 20 percent, which typically occurs 2 to 4 weeks after R6.
• The best indicator for harvesting is the moisture content of the kernels: the best range is between 28% and 21%: a content of 25% of moisture is the most common. Harvesting when moisture is higher means spend money for drying the grain and also means damage the grains during the trashing; on the other hand, waiting for moisture lower than 21% means risks of lodging and stalks breaking. However, when the bottom of the kernels is black (black layer stage) the corn is fully mature; after that stage, the further maturation process is simply due to losses of moisture from the kernels. Tips for losses estimate at harvesting: each ear lost means about 50 kg corn lost per hectare; on average, a loss of 30 kernels per square meter means about 100 kg corn lost per hectare.