ABSTRACT: Irrigated rice in the state of Rio Grande do Sul (Brazil) has shown significant growth in yield in recent years due to improved management practices, especially in regard to fertilizer use. However, the response curves that led to the current fertilizer recommendations do not consider integrated systems prevailing in rice-producing regions that have adopted the practice of integrated crop-livestock systems. The aim of the present study was to evaluate the effectiveness of current fertilizer recommendations for irrigated rice in lowland soils in Rio Grande do Sul under integrated crop-livestock systems for different periods of time. The experiments were performed in the 2012/2013 growing season on four farms in the state with different forage species under cattle grazing. In these areas, fertilizer recommendations were made based on previous soil analyses, and treatments consisted of fractions of the currently recommended application rates. At the end of the crop cycle, the percentages of maximum technical efficiency (PMTE) and maximum economic efficiency (PMEE) of NPK fertilizers, and increases in yield and net income provided by PMEE were determined. Rice yield increased and fertilizer response decreased over time in a rice-beef cattle integrated system. The highest incomes with fertilization of irrigated rice occurred at lower application rates than those recommended by soil analysis.

As aplicações sucessivas de dejetos de suínos, na forma líquida, podem incrementar os teores de carbono orgânico total no solo e de nutrientes, bem como alterar os atributos relacionados à acidez do solo, porém há pouca informação acerca do efeito do uso de cama sobreposta de suínos sobre os atributos da acidez do solo e o carbono orgânico. Este trabalho objetivou avaliar a alteração nos teores de carbono orgânico e nos atributos relacionados à acidez em um solo com histórico de aplicação de dejetos líquidos de suínos e cama sobreposta. Após oito anos da instalação de um experimento localizado no município de Braço do Norte, Santa Catarina (SC), sobre um Argissolo Vermelho, foram coletadas amostras de solo nas camadas de 0-2,5, 2,5-5, 5-10, 10-15, 15-20 e 20-30 cm, em tratamentos sem aplicação de dejeto e com a aplicação de dejetos líquidos de suínos e de cama sobreposta de suínos em duas doses: para suprir uma e duas vezes a necessidade de N para a sucessão milho e aveia-preta. O solo foi seco, moído, passado em peneira e submetido à análise de carbono orgânico total, pH em água, Al, Ca e Mg trocáveis; com base nos dados obtidos, calcularam-se a capacidade de troca de cátions efetiva (CTCefetiva) e a pH 7.0 (CTCpH7,0), H+Al e a saturação por bases e Al. Os resultados mostram que as aplicações de dejetos líquidos de suínos e cama sobreposta durante oito anos aumentaram o teor de COT e a CTC no solo até a profundidade de 30 cm. A aplicação de cama sobreposta de suínos diminuiu os valores de acidez ativa e de saturação por Al e aumentou os valores de saturação por bases até 30 cm de profundidade. O uso de dejetos líquidos por oito anos não provocou nem acidificação nem correção da acidez do solo, indicando que o efeito desse resíduo nos atributos da acidez do solo foi pequeno ou nulo.

Successive applications of liquid swine waste to the soil can increase the contents of total organic carbon and nutrients and change acidity-related soil chemical properties. However, little information is available on the effects of swine waste application in solid form, as of swine deep-litter. The objective of this study was to evaluate alterations of organic carbon and acidity-related properties of a soil after eight years of pig slurry and deep-litter application. In the eighth year of a field experiment established in Braço do Norte, Santa Catarina (SC) on a sandy Typic Hapludalf samples were taken (layers 0-2.5; 2.5-5; 5-10; 10-15; 15-20 and 20-30 cm) from unfertilized plots and plots with pig slurry or deep-litter applications, providing the simple or double rate of N requirement of Zea mays and Avena strigosa in rotation. Soil total organic carbon, water pH, exchangeable Al, Ca and Mg, and cation exchange capacity (CECeffective and CECpH7.0), H+Al, base saturation, and aluminum saturation were measured. The application of pig slurry and deep-litter for eight years increased total organic carbon and CEC in all soil layers. The pig slurry and deep-litter applications reduced active acidity and aluminum saturation and increased base saturation down to a depth of 30 cm. Eight years of pig slurry application did not affect soil acidity.