Integrated crop-livestock systems in paddy fields: New strategies for flooded rice nutrition

Integrated crop-livestock systems (ICLSs) appear as a good alternative to increase nutrient use efficiency (NUE) in rice (Oryza sativa L.) through the improvement in nutrient cycling and soil chemical attributes in paddy fields. The objective of this study was to evaluate the impact of an ICLS on soil chemical attributes and on the fertilization requirement of N, P, and K by flooded rice in the Brazilian subtropical region. Nutritional status, yield, and NUE of flooded rice were evaluated by fertilization trials through rice response to different fertilization rates of N, P, and K. Soil chemical attributes were evaluated at the beginning of the experiment and 30 mo later. Different fertilization rates were applied in two systems: (a) a conventional system (CS), based on intensive tillage, rice monocropping and winter fallow, and (b) ICLS, characterized by no-tillage and winter cattle grazing in annual ryegrass (Lolium multiflorum Lam.) pasture. Rice shoot accumulation of N, P, and K was greater under CS than ICLS at all fertilization levels. On the other hand, higher rice yields were observed under ICLS at almost every fertilization level, suggesting higher NUE than CS. In addition, rice yield was increased by 40% by fertilization of P and K under CS, whereas no response was observed under ICLS. These benefits were possibly related to greater nutrient cycling and greater synchronism between rice's nutrient uptake and nutrient release of the soil. Our results indicate that the adoption of ICLS ensures greater NUE becoming a system less dependent on external inputs.