Alternativas tecnológicas podem minimizar os impactos negativos dos dejetos líquidos de suínos (DLS) sobre o ambiente, além de melhorar seu efeito como fertilizante. O objetivo deste trabalho foi comparar o efeito do modo de aplicação dos DLS e da ureia, com e sem o uso de inibidor de nitrificação dicianodiamida (DCD), sobre a evolução dos teores de N mineral no solo, nas cultura de milho e trigo, em plantio direto. O trabalho foi conduzido em Cambissolo Húmico Alumínico, utilizando o delineamento experimental de blocos ao acaso com quatro repetições, em esquema fatorial 2 x 5. Os tratamentos foram dois modos de aplicação ao solo de DLS e ureia (injeção x aplicação superficial) e cinco tratamentos com as fontes de N (ureia; ureia+DCD; DLS; DLS+DCD e testemunha sem N). Os tratamentos foram avaliados em cultivo de milho na safra 2012/2013 e de trigo na safra 2013. As amostras de solo foram coletadas nas profundidades de 0-5, 5-10 e 10-20 cm. A adição de DCD aos DLS e à ureia preserva por mais tempo na forma amoniacal o N dos fertilizantes. A injeção dos fertilizantes aumentou os teores de amônio em relação à aplicação superficial.
Phosphorus (P) reacts with chemical and mineralogical constituents in the soil, mainly in tropical and subtropical soils. Therefore, strategies have been used to reduce the adsorption of P to the soil, among them, the formation of complexes that could decrease P adsorption to the soil. Two experiments were carried out to evaluate the formation of organic acid-Fe-P complexes in the laboratory and the efficiency of these complexes on the growth of wheat plants (T. aestivum) grown under greenhouse conditions. In experiment 1, seven low-molecular-weight organic acids (OA) were selected and a protocol for the formation of complexes between organic acid and Fe3+ at pH 4.0 was performed. After stirring, P was added to the organic acid-Fe complex to form the ternary complex. The remaining P was evaluated to determine the amount of P in the complex. In experiment 2, the three OAs which had the largest amount of complexes were selected, together with a treatment with soluble P and a control. Wheat was grown in potted soil in a greenhouse for 34 days. The amount of ternary organic acid-Fe-P complexes formed varied from 5 to 42% of the added P. However, when these complexes were added to the soil, in treatments with greater amount of complex formed there was lower growth of wheat. Thus, the ternary complex with organic acid-Fe-P has little effect on the performance of wheat plants.
This study aims to evaluate the influence of the ground cover rate by crop residues and the rain time elapsed after the application of liquid swine slurry (LSS) under losses of water, sediments, and phosphorus (P). The study was carried out under a Humic Cambisols. Two areas were delimited: with and without the application of LSS. Each area was subdivided into four levels of crop residues: 5%, 35%, 65%, and 95%. Vegetable residues present in the area, from corn and black oat, were used. Three collecting gutters of 0.60 m² were installed in each subplot. Simulated rain was carried out on these, and the runoff volume collected for quantification and determination of losses. With LSS application, increase in the cover rate by crop residues reduces 0.3 mm h-1 the runoff volume and 1.67 mg m-2 reactive soluble P (H2O-P). The sediment losses in the first collection after the beginning of the rain were 23 times lower in the soil with 95% ground cover than in the soil with 5% ground cover. The loss of total P (total-P) decreases with the increase of the ground cover of the soil and increases in the same way with the increase of the time.
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