Chemical management in off-season corn

Obtaining high corn productivity, without loss of quality, requires correct management throughout the crop cycle. Hybrid suitable for the region's climate condition and sowing time, population adjustment, pest management, choice of fungicides, times and number of applications are some factors that can contribute to better results in the second harvest.

Corn is the cereal with the largest production volume in the world. Brazil occupies a position among the world's main producers and exporters. As it is a C4 plant, corn is one of the cereals with the greatest potential for grain production. This characteristic, combined with its bromatological properties, makes it of great importance as a source of energy for human and especially animal nutrition. The estimate of Brazilian production in the 2013/14 harvest is 79 million tons (Conab, 2014) and the main destination of this production is animal consumption, corresponding to 58% of this volume and 78% of the domestic corn market (Figure 1) . Among the corn consuming segments in Brazil, the ones that consume the most are poultry and swine farming (Figure 1). These sectors are demanding regarding the quality of corn, as the cereal is responsible for approximately 2/3 of the ingredients used in food and has a direct effect on the animals' production rates.

Brazilian corn production has increased in recent years, mainly due to the expansion of cultivation areas and increased productivity in the 2nd harvest, also known as “safrinha”. From the 2011/12 harvest onwards, 2nd harvest corn production surpassed the 1st harvest (Figure 2). Cultivating corn in the 2nd harvest has some benefits, such as: the possibility of carrying out two harvests per year, reducing the cost of fertilization by using the nutrients made available by soybeans (mainly N), using the property's machines, diluting fixed costs, profitability when compared to other winter crops and guarantee of commercialization of production. However, this monoculture cultivation system, combined with the favorable environment, promotes an increase in necrotrophic diseases, such as helminthosporiosis (Exserohilum turcicum), cercosporiosis (Cercosporazeae-maydis), white spot (Pantoea ananatis), fusariosis (Fusarium moniliforme e F. verticillioides) and diplodia (Stenocarpella macrospora and S. maydis), causing lesions on leaves and rot on ears and stalks.

The states of Mato Grosso and Paraná are the two main corn producers in the 2nd harvest. However, Paraná has faced problems related to the quality of corn grains, due to climate instability and the possibility of frost and rain occurring during the pre-harvest phase of the grains. The majority of corn production in Paraná is used for animal feed.

The Consolata Agroindustrial Cooperative (Copacol), located in western Paraná, has suffered from the instability of the 2nd corn harvest, 100% of the corn produced by its members is consumed in the integration of poultry, pigs, cattle and fish. Due to the need to improve the quality of corn, Copacol has developed a series of experiments in recent years at its Agricultural Research Center (CPA Copacol) to identify the causes of the poor quality of corn received in the 2nd harvest.

The main management factors that affect grain productivity and quality in the 2nd harvest are related to genetics, disease management, population adjustment and pest management. Table 1 summarizes the results of an experiment conducted with 49 different hybrids depending on fungicide management. In the plots with fungicide, three applications of the products azoxystrobin + cyproconazole + propiconazole were carried out, at doses of 80g of active ingredient/ha + 32g of active ingredient/ha + 100g of active ingredient/ha, respectively, in the crop development phases: V8, VT and VT+20 days.

Table 1 shows a reduction in the weight of a thousand grains (PMG) of more than 10%. The reduction in PMG has a direct effect on the reduction in productivity and occurs due to the premature death of plant leaves due to pathogen attack (Figure 6). The leaves are the place where the production of photoassimilates occurs, which would be translocated and result in the complete filling of grains. With the death of the leaves, production ceases and grain filling is compromised (Figure 7). An average gain of 49kg/ha was observed for the 1.427 hybrids, and for some hybrids this increase was greater than 3.000kg/ha. In another experiment carried out in 2013 with two hybrids and five plant populations with and without fungicide (Figure 3), gains in productivity were 1.250kg/ha and 1.630kg/ha for the hybrids AG 9010 PRO and P 3340 H, respectively. . The consistency of the results observed with the application of the fungicide can be explained by the fact that it is the only strategy adopted to manage diseases in the corn production system in the second harvest.

Stem failure was reduced by 30% with the application of fungicide in the trial. With the collapse of the leaves, in an attempt to guarantee the survival of the species, the corn plant reallocates its stalk reserves to meet the demand for grains. As a result, the culms become fragile and susceptible to tipping over, which can result in losses at harvest time. Lower grain moisture was still observed at the time of harvest in the area without fungicide application. This occurs due to the premature death of the plants, which stops the flow of water and nutrients to the ears.

In addition to the increase in productivity, there was a reduction in the content of damaged grains, reducing from 8% to 4,7% with the application of fungicide, on average across the 49 hybrids. In terms of percentage reduction, this means a decrease of more than 40%. In this trial there was also great variation regarding hybrids, as can be seen in Figure 9. In the trial conducted in 2013 (Figure 3), there was a reduction of 5,7% (19,4% to 13,7%) and 1,9% % (5,8% to 3,9%) with fungicide application for the hybrids AG 9010 PRO and P 3340 H, respectively. The assessment of the content of damaged grains has been used to characterize the quality of corn, as high levels result in loss of commercial value of corn for producers, in addition to subsequent complications for feed production.

The presence of damaged grains increases the chances of the presence of mycotoxins in the grains. The production of mycotoxins by the fungus depends on the climatic conditions faced during grain colonization. When they occur, mycotoxins cannot be eliminated by industrial processes, resorting to the use of adsorbents that increase the cost of feed. The main mycotoxins present in corn grains are aflatoxins (Aspergillus flavus), fumonisins, mycotoxinT-2 and zeralenone (Fusarium spp.). When ingested by animals, there is a reduction in weight gain, diarrhea, liver problems, reproductive problems and an increase in feed conversion, resulting in a decrease in production rates and economic losses.

Although the damaged content is used to characterize the quality at the time of grain delivery by the producer, there is no correlation with grain bromatology, which has a direct implication in the manufacture of feed. Table 1 shows the values ​​of these characteristics, with higher levels of metabolizable energy and ether extract (fats) and lower levels of crude protein in grains to which fungicide was applied. This is explained by premature death and incomplete grain filling. The part of the grain that presents the greatest losses is the endosperm, as it is formed after the embryo. The protein concentration in the embryo is around 18% compared to 7% in the endosperm. As for starch, concentrations vary from 8% for the embryo and 80% for the endosperm. Thus, a reduction in the endosperm/embryo ratio results in an increase in protein content and a decrease in starch content, the main contributor to the grain's metabolizable energy. In addition to the effect of fungicide application, a large variation in bromatological characteristics was observed depending on the hybrids studied. The full data can be accessed on the Copacol/Agricultura/CPA website. As an industrial implication, corn grains with a lower amount of metabolizable energy increase feed production costs due to the need to supplement this energy with other ingredients such as soybean oil.

Population adjustment for each hybrid is an important management factor for obtaining high corn yields. However, the increase in plant population linearly increases the content of damaged grains (Figures 4 and 5). This experiment was conducted in three locations, with two different hybrids by the CPA Copacol team. The increase in the number of plants per area favors the establishment of pathogens by creating a more favorable microclimate for the establishment of diseases, in addition to increasing interspecific competition (between corn plants), which leaves the host more vulnerable to infection. The increase in damaged grain levels also occurs due to the formation of smaller grains at the tip of the cob, with incomplete filling, grains that are normally more sensitive to sprouting in humid conditions and also to fungal attack. Sometimes it is necessary to give up maximum productivity in favor of quality grains.

Pest management 

Adequate pest management in the 2nd harvest is essential to obtain high yields with grain quality. Bedbugs (Dichelops sp.) and caterpillars (Spodoptera frugiperda) are the main problems. Stink bug attacks generate dominated plants, which are more susceptible to producing damaged grains. The use of tools such as biotechnology has brought important advances in improving grain quality by preventing damage to corn cobs (Figure 8). They are a gateway for humidity and fungus on the cob.

Due to the destination of Brazilian corn, the market has penalized producers who do not meet quality standards, as low quality products are a complication for Brazilian cereal producers. Obtaining high corn productivity without loss of quality requires correct management throughout the crop cycle and is fundamental to the economic success of the activity. The choice of the appropriate hybrid for the region's climate condition and sowing time, population adjustment, pest management, choice of fungicides, times and number of applications are some factors that can significantly contribute to improving quality. of corn grains grown in the second harvest.

Tiago Madalosso, Fernando Fávero, Agricultural Research Center - Copacol 

Article published in issue 189 of Cultivar Grandes Culturas.