Remoção de nutrientes em lavouras de milho de alta produtividade destinadas à ensilagem

Abstract

Corn has been the most used plant for the production of silage of high bromatological value, aiming at feeding dairy cows of medium to high productivity. Several techniques have been proposed to increase the productivity of crops and the bromatological quality of silages, including new agricultural practices in the implantation and management of crops and also new procedures during cutting and ensiling. In the present work, results regarding soil fertility, nutritional status, dry matter production and nutrient removal in four high-yield corn crops are presented. The evaluations were carried out in rural properties in the Zona da Mata Mineira, which intensively use the production of corn silage to feed dairy cows. Samplings for the evaluation of soil fertility, nutritional status and production and accumulation of nutrients were carried out systematically. In the female inflorescence emission phase, the leaf blade was analyzed for N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn contents, systematically sampling seven areas of 3, 5 m2 each. When the aerial biomass of the plants presented an average of 33% of dry matter, the forage production of the crop was evaluated, sampling again, in the same areas used to evaluate the soil fertility and the nutritional status of the plants. The corn was cut at about 20 cm above the ground and the plant material was weighed and passed through a forage chopper. Subsamples of this material were analyzed for N, P, K, Ca, Mg and S contents. Based on the concentration values of N, P, K, Ca, Mg and S in the dry matter, and the dry matter production, calculated the accumulation of nutrients in the aerial biomass of the plants. Soil fertility in the crops of the small rural properties assessed was medium to high, with phosphorus contents ranging from 10 to 20 mg dm-3, while for potassium this variation was from 40 to 89 mg dm-3. In the soils of the four analyzed crops, there was no exchangeable aluminum in the 0 to 20 cm layer, and in the 20 to 40 cm layer, aluminum saturation in crops 1 and 3 was also small, less than 5%. It was found that all crops had adequate mineral nutrition for both macros and micronutrients. Dry matter production and nutrient accumulation in corn area biomass in crops were high. The average value of dry matter accumulation was close to 20.0 t per hectare, and the average removal of nutrients, by harvesting the aerial part of the corn for silage, was 247, 34, 245, 34, 23 and 22 kg per hectare for N, P, K, Ca, Mg and S, respectively.

Key words: Restitution fertilization, corn mineral nutrition, production technologies.