Abstract
Abstract: The objective of this work was to determine the nitrogen, phosphorus, and potassium released by N-fertilized Urochloa brizantha straw, desiccated before sowing of no-tillage soybean (Glycine max) in succession. The pasture was grown in three paddocks, each fertilized with one N rate (0, 150, or 300 kg ha-1), and assessed at two desiccation periods (60 or 15 days before soybean sowing), in four replicates. Nitrogen fertilization of U. brizantha pasture increases N and K cycling and the release of these nutrients to the subsequent soybean crop. The quantity of K released by U. brizantha straw fertilized with 150 or 300 kg ha-1 N (about 80 kg ha-1 K) offsets that contained in an export of up to 4 Mg ha-1 soybean grains, assuming zero K losses in the system. An early desiccation of the U. brizantha pasture does not improve K uptake by the soybean crop, since 50% of the nutrient is released in the first 20 days after desiccation. The dynamics of P release from U. brizantha straw (about 6 to 10 kg ha-1 during the soybean crop) is not influenced by N fertilization and the time of pasture desiccation.
Highlights
The management of Crop-Livestock Integration Systems (ICLS) in a no-tillage (NT) system can increase the use efficiency of resources, as nutrients, to ensure high yields (Salton et al, 2014)
The pasture was grown in three paddocks, each fertilized with one N rate (0, 150, or 300 kg ha-1), and assessed at two desiccation periods (60 or 15 days before soybean sowing), in four replicates
The quantity of K released by U. brizantha straw fertilized with 150 or 300 kg ha-1 N offsets that contained in an export of up to 4 Mg ha-1 soybean grains, assuming zero K losses in the system
Summary
The management of Crop-Livestock Integration Systems (ICLS) in a no-tillage (NT) system can increase the use efficiency of resources, as nutrients, to ensure high yields (Salton et al, 2014) To this end, ICLS is appropriate to increase the profitability and sustainability of soybean [Glycine max (L.) Merrill] yields in the tropical and subtropical regions of Brazil (Franchini et al, 2014). The use of pasture of the genus Urochloa, integrated with grain production, is a feasible way of improving and sustaining NT systems in the long term (Costa et al, 2014) Forage species of this genus, apart from the high shoot and root biomass production, favor a longer period of residue conservation on the soil, due to the high carbon/nitrogen ratio, which slows down decomposition and increases the suitability for hotter regions, where decomposition is fast (Franchini et al, 2014). The nutrients released by the decomposing straw contribute to meet the nutritional needs of subsequent soybean (Cavalli et al, 2018)
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