Efeito dos sistemas integrados de produção agropecuária sobre as frações de fósforo e potássio em Planossolo

Abstract

The present study was developed with the aim of evaluating the influence of different arrangements of integrated agricultural production systems in lowlands on the contents of P fractions (soluble, available, organic, inorganic, HCl and total) and K (available, exchangeable, non-exchangeable) from the ground. Assessments were carried out after the end of the second cycle in a long-term research protocol. The period of each cycle was four years (2014-2017 and 2018-2022). The research protocol evaluated five production systems with different arrangements, which varied in relation to crop diversity, temporal frequency of irrigated rice cultivation and animal grazing time. O (S1): rice cultivation – fallow without animal grazing (off-season) - rice; S2: rice – ryegrass (with moderate grazing) – rice; S3: rice – ryegrass (with moderate grazing) – soybean – ryegrass (with moderate grazing) (with moderate grazing) – rice; S4: rotation between rice, soybeans, corn and sudan grass in the summer and ryegrass and white clover pasture in 2013 or ryegrass and Persian clover in the years 2014 to 2018 in the winter period; (with moderate grazing) S5: ryegrass + white clover + cornichão – succession field (three years) (with moderate grazing) – rice. To assess K and P content in the soil, samples were collected at the following depths: 0-2.5 cm, 2.5-5 cm, 5-10 cm, 10-20 cm and 20-40 cm. In relation to phosphorus stocks, in the 0 20cm layer, systems with the presence of animals (S2, S3, S4 and S5) increased an average of 241% available phosphorus, 19% organic P and 35% organic P. total. These responses are linked to minimal soil mobilization, presence of animals for a longer period, for the benefits of pastures and grazing, in addition to the positive balance of k and P, due to the fertilization carried out to correct these nutrients, above critical levels. Potassium analyzes indicated that the adoption of systems with SIPA contributed to the increase in available and exchangeable potassium fractions, with system 5, which presented the highest levels at all depths analyzed for these fractions. The highest levels for both nutrients were found in soils subjected to the greatest diversity of integrated activities (S4 and S5), making it possible to infer that SIPAs influenced the increase in levels and availability of these in the soil, in addition to the increase in P stock, having in view, that the results of the P and K analyzes indicated that the monoculture system without the presence of animals, presented lower levels of these elements in relation to SIPAS.