Estado nutricional, produtividade e remoção de nutrientes pelo híbrido de milho BR9308 YG em duas safras

Abstract

Dairy farming is of great socioeconomic importance for several municipalities in Brazil, since it employs large numbers of people from different social classes. Feeding of high-yield dairy cows consists basically of concentrated feed and corn silage, and feeding alone is the most expensive item for milk production. The present study describes the main technologies used in high productivity maize production systems for silage in the municipality of Mercês, Zona da Mata Mineira. The study was conducted on a dairy farm from August 2015 to March 2017. The farm is situated at an average altitude of 525 m. The climate of the region is tropical at high altitude with rains during the summer and annual average temperature around 18 ° C, with variations between 24 ° C (mean maximum) and 13,8 ° C (average minimum). The average annual precipitation in the last 30 years was about 1,200 mm. Before the implantation of the study, soil samples were collected from a forage production area of the farm, in the layers from 0 to 20 and from 20 to 40 cm and from the results of the chemical analysis, in September of 2015, the application of limestone and gypsum, aiming at raising the base saturation to 60% in the arable layer and, to reduce the saturation by aluminum in the layer of 20 to 40 cm. In the first week of October, 2015, the soil was reassembled again. Three days later, corn sowing, hybrid BR9308YG, was performed. In the fertilization of planting, the fertilizer 10-30-10 was used in the dose of 450 kg per hectare. In the phenological stage of three pairs of leaves, the fertilization was done in cover using 1.000 kg of the fertilizer 20-00-20 per hectare. In the phase of the emission of female inflorescence, the nutritional status of the plants was evaluated. In the middle of January 2015, when aerial biomass of the plants presented on average 33% of dry matter, the forage production of the crop was evaluated, systematically sampling seven areas of 10.0 m2 each, in the the same areas used to evaluate the nutritional status of plants. The corn was cut about 20 cm above the ground and the plant material was weighed and passed in forage chopper. Subsamples of this material were dried in an oven and analyzed for nutrient and protein contents. Seeding of the second year of study was carried out in the first week of October 2016. There was no need for a new application of limestone and gypsum. The soil was reassembled and three days after corn sowing, hybrid BR9308YG. In fertilization, weed control and sampling for nutritional status evaluation and forage production, the same procedures were adopted for the first year of evaluation. The results were submitted to analysis of variance to verify the experimental variability in each year and the effect of the year of cultivation on nutritional status, crop forage production, nutrient removal and nutrient balance in the soil-plant system. There was no effect of the year of cultivation on the macro and micronutrient foliar contents and, in the two years of cultivation, the plants had foliar tors adequate for all the nutrients. For the production of forage and nutrient accumulation in aerial biomass of maize, there was also no effect of year of cultivation. In the average of the two years the accumulation of natural matter and dry matter in the aerial biomass of maize was respectively 61.7 and 20.0 t per hectare. The average accumulation of N, P, K, Ca, Mg and S in aerial biomass was 253, respectively; 39; 240; 43; 25 and 25 kg per hectare. The adopted production system allowed to obtain high productivity of forage and great stability between years.