Agriculture Business Week

Talking to many farmers across the country, I found that majority of them had been planting corn in the same land twice a year for as long as they can remember. They plant corn during the wet season, just before the dry season starts, and plant another round – which they call “palusot” – to take advantage of sufficient rains and dry periods at harvest. And so the cropping cycle goes on. This is especially true in Cagayan Valley and Mindanao where growing conditions are tough, but because of the recent advances in hybrid corn technology things have become manageable.

Corn uses less water than rice, can be grown on a wide range of soil types, and can adapt to various planting methods. There are plenty of hybrid varieties to choose from and there is a steadily growing market for feeds. Corn grains are durables (in contrast to “perishable” fruits and vegetables) so rushing these grains to end-users is not an issue after proper drying and storage. In short, who would not want to plant corn continuously? With these factors, even Ilocos and Central Luzon growers (corn-after-rice) would want to plant corn all year long if not for the severe monsoon rains which occur from July to September that will surely submerge their low-lying fields. In the Visayas and in Bicol, they make sure to plant only on well-drained soils or on rolling fields.
There is, indeed, an economic advantage for growing corn non-stop but we should be aware that we also put some strain or stress on the farm we till. This article would address best practices for corn-after-corn production practices with emphasis on hybrid selection, high crop residue challenges related to diseases, soil fertility, and weed management.

HYBRID SELECTION
Selecting the right hybrid is an internal part of a successful corn-after-corn production. A corn grower should always ensure to
• Select hybrids with proven performance under diverse environments and stresses their field may encounter;
• Select hybrids with above average drought tolerance. Under corn-after-corn system, root mass may be reduced and such may not prepare the corn plant for limited water conditions;
• Select the right hybrid maturities that match corn plantings dates and forecasted climatic conditions. If drought is expected, it is wise to use early maturing hybrids; and
• Choose the highest performing genetics with the defensive traits required for this production system.

For better understanding of these traits, seek the assistance of your Pioneer agronomist in selecting hybrids for corn-after-corn.

CROP RESIDUE AND DISEASES
In cropping systems where great amounts of residue are left in the soil surface, corn diseases may become an issue. Pathogens or microbes survive in corn residue and disease builds up over time. This is especially true in the disease-prone areas of Mindanao, Panay, and Bicol. Sometimes, planting too early in a high-residue seedbed can increase the chances of corn seedling diseases (seedling blight, for example). This can be avoided through strip tillage or removal of the residues from the rows.

Leaf diseases such as gray leaf spot, northern leaf blight, and diplodia leaf blight are known to have increased in Mindanao due to long-term, high-residue farming. This could also be possible in the cool areas of Panay and Bicol where corn-after-corn had become an acceptable farming practice. Stalk and ear rots such as Gibberella, Diplodia, Fusarium, and Aspergillus also survive in crop residue and increase in high-residue systems. Burying (or plowing under) crop residue by tillage may be an option but all growers should select hybrids with good disease resistance and standability. Often times, stalk rots accompany leaf diseases so monitoring stalk quality and timely harvest is helpful when leaf diseases occur. The practice of manual ear-picking here in the Philippines becomes more expensive on fields with severe lodging brought about by diseases.

If ear rots are found, late-season scouting can help growers make informed decisions about harvest timing, postharvest, grain handling, and storage and utilization. For example, grains with significant ear rot symptoms from the field should be dried quickly to 15 percent or less at high temperature. The lower the moisture content in storage, the lower the risk of mycotoxin(amag) development

SOIL FERTILITY AND NITROGEN
In corn-after-corn, many farmers are not aware of the value of thorough soil testing and the availability of local nutrient recommendations coming from LGUs and seed companies. Soil tests are needed to measure soil pH (acidity or alkalinity, not lower than pH 5.5), organic matter content (nitrogen), phosphorus (P), and potassium (K). A balanced level of P and K applied as basal can improve efficiency in nutrient uptake.

Unlike legumes (or beans), corn residues tie up much more nitrogen as they decompose in the soil. This is why using the same level of N fertilizer in the succeeding season of corn after corn system does not really bring any additional yield. Not unless growers increase their N rates by 40kg to 50kg N/ha. It really pays to have a soil test or obtain local recommendations. Recent US studies however, revealed that regardless of N levels, corn-after-corn never equalled a corn rotated to soybeans.

WEED MANAGEMENT
Watching ut for weeds is a more important issue among corn-after-corn systems as compared to corn-after-rice. In Central Luzon, farmers have attested that weeds are more problematic in their off-season crop than corn following their rice crop in the wet season. Hence, growers should monitor fields for any increase in specific weed pressure and employ proper control especially among glyphosate-ready (RR corn) fields. Alternating use of herbicide mode of action and use of mixtures will help ensure long term success of weed management and prevent weed shifts or weed resistance. Watch out for volunteer plants also. These are plants that have emerged from ears or brains left in the field after harvest. Farmers should then strive to reduce stalk breakage and ear drop.

ROTATION EFFECT AND STRESS
The so-called “rotation effect” is an unexplained benefit that results in better yields with crop rotation, even though the limiting factors are being addressed in continuous cropping. Where yield potential is low, yield reductions become greater for corn-after-corn vs. rotated corn cycle. Such observations led to the idea that generally, crop rotation renders the corn more tolerant to yield limiting stresses, in particular to moisture extremes. Experts implicate the root system as the most likely source of the problem. In corn-after-corn systems, soil compaction can be one likely cause but it could also be more of neglect on the part of the grower. A vast majority of our growers do not have access to soil testing or simply unaware that it is absolutely necessary for the sustainability of their valuable resource.

MANAGEMENT SUGGESTIONS FOR CORN-AFTER-CORN
• Choose fields that are best-suited for corn-after-corn system. Fields should have good drainage, medium-textured soils with ample water holding capacity, and adequate P and K levels.
• Manage corn borers using Pioneer 30T80, 30Y80, 30T35, 30Y34, and 30T44. Your local Pioneer agronomists and sales representative will gladly assist you in choosing which is best-suited in your area.
• Select hybrids with appropriate maturities to suit your needs. Early maturing hybrids will always have an advantage.
• Manage nitrogen carefully. A combination of N during basal and side dress applications may help limit effects of N losses due to leaching and denitrification in wet periods.
• Walk in the field regularly and monitor to identify any problems early. Look for stand count issues, nitrogen shortages, insect build ups, outbreak of disease, weed problems, and effects of moisture stress.
• Monitor fields for leaf diseases and stalk and ear rots. They can be controlled by managing residues properly and selecting resistant or tolerant hybrids.
• Be diligent to prevent soil compaction on corn-after-corn fields.

FREQUENTLY ASKED QUESTIONS
Q: Do you recommend top cutting in corn, days prior to harvest or when the husks starts to dry? What are the benefits and disadvantages?
A: We do not recommend top cutting (or tadaw in Ilocano) at any ‘ reproductive stage of the crop. It has been proven that grain yield can be reduced by as much as 20 percent if tadaw is carried out at around 80 percent for a full season hybrid. Grain quality would, also deteriorate as the crop is forced to mature earlier than expected. Other than having an early harvest and a good source of forage, we don’t see any advantage in doing tadaw. For as long the grains are not yet mature, the ears are still receiving food from the upper leaves and stalks.