ABSTRACT
ABSTRACT: The goal of this study was to quantify the water, soil, and soluble nutrient losses during high-intensity rainfall simulated in two soil preparation systems with four sources of fertilization. Forty-five days after the corn seeding, a 120 mm h-1 intensity rainfall was simulated during 90 min in field plots with conventional tillage (CT) or no-tillage (NT). Each system had four repetitions with the fertilizer treatments, including without fertilization, mineral, urban waste compost (UWC), and pig slurry. P, K, Ca, and K concentrations were measured in soluble form, in addition to electrical conductivity, pH, water, and soil losses. As expected, the greatest soil losses occurred with CT; however, the greatest water losses occurred with NT. Among the fertilizers, UWC was more efficient because it had the highest infiltration rates. The concentrations of P, K, Ca, and Mg did not exhibit any interaction between fertilization and soil tillage treatments. K was the nutrient that presented the greatest losses (kg ha-1) at the end of the simulated rainfall because of the highest concentrations (mg L-1) added to high runoff coefficients of 45% for CT and 77% for NT. Thus, the evaluated system with cover crops and minimum soil tillage was not sufficient to control nutrient transfer in the soluble form during intense rainfall events.
RESUMO: O objetivo do trabalho foi quantificar as perdas de água, solo e nutrientes na forma solúvel durante chuva simulada de alta intensidade, em dois sistemas de preparos do solo e quatro fontes de adubação. Quarenta e cinco dias após a semeadura do milho, uma chuva com intensidade de 120 mm h-1 foi simulada durante 90 minutos, em parcelas de campo sob preparo convencional (PC) e plantio direto (PD). Em cada preparo há quatro repetições dos tratamentos com adubação: sem fertilização, mineral, composto de lixo urbano (CO), e dejetos de suíno. Foram mensuradas as concentrações de P, K, Ca, Mg na forma solúvel, além da condutividade elétrica - Ce, pH, perda de água e solo. Conforme esperado as maiores perdas de solo ocorreram para o PC, entretanto, as maiores perdas de água no PD. Entre as adubações, o CO foi o mais eficiente, pois apresentou as maiores taxas de infiltração. As concentrações de P, K, Ca e Mg não apresentaram interação entre os tratamentos de adubação e os tratamentos de preparo do solo. O K foi o nutriente que apresentou as maiores perdas (kg ha-1) ao final da chuva simulada, devido as maiores concentrações (mg L-1) somado aos altos coeficientes de escoamento superficial sendo 45% para o preparo convencional e 77% para o plantio direto. Ao final, o sistema avaliado com plantas de cobertura e mínimo revolvimento do solo não foi suficiente para controlar a transferência de nutrientes na forma solúvel durantes eventos de chuvas intensas.
ABSTRACT
Aim: This study was carried out to ameliorate acid sulphate soil (ASS), improve soil nutrient content and the soil quality by employing the use of organic and reduce mineral fertilisation. Study Design: Treatments were arranged according to a completely randomised block design, in triplicates in a greenhouse. Methodology: Three fertiliser regimes at three doses (mineral N, P, K (MIN-control (CK), NPK,2NPK), empty fruit bunch compost (COM-CK, EFB, 2EFB) and poultry manure (MAN-CK, PM, 2PM)) were used. The effect of organic and reduce mineral fertilisation on soil pH, nutrient level, microbial count (colony forming unit (CFU)), microbial biomass (Cmic) and enzyme activity were investigated. Results: The study revealed that the MAN (PM and 2PM) led to a remarkable increase in bacterial and fungal CFU, Cmic, microbial activity, soil organic carbon (SOC) and nutrient content (N, P and K). MAN also stimulated enzyme activities (β-glucosidase (BG), acid phosphate (ACP) and protease (PRO)), but it did not affect the pH of the acid soil later. Soil pH decreased and NPK and 2NPK were not significant. However, microbial count was decreased significantly at 2NPK compared to the control even though the nutrient level was elevated to some extent. In COM, soil pH and nutrient level increased, but the fungal CFU, Cmic and BG were significantly low. Considering the high heavy metal content of the compost we ascribed these observations to a disturbance from the metal contamination due to high qCO2 values at the end of the study, The effect of dose was most pronounced in MAN and least pronounced in MIN. Conclusion: Our result suggests that, for amelioration and quality improvement of ASS of tropical coastal agroecosystem, manure fertilisation supplemented with lime or EFB compost (of good quality) could be recommended while maintaining favourable moisture conditions in the soil.