Nutrient Balance and Use Efficiency in Agricultural Lands in the Vermelho River Watershed, Upper Pantanal, Brazil

Agricultural systems play a key role in achieving many of the Sustainable Development Goals, established by the United Nations, given the current challenge of producing enough food to feed a global population that is expected to reach 10 billion people by 2050. More efficient and sustainable use of nutrients in agriculture is an important step to increasing production while minimizing threats to natural ecosystems and resource depletion. In this study, we developed a system nutrient balance for nitrogen (N) and phosphorus (P) to evaluate nutrient use practices in cropping and grazing systems in the Vermelho River watershed (VRW), Upper Pantanal, Brazil, and investigated options to improve N and P use efficiency (NUE and PUE). Our results show P balance in cropping systems are positive while those in grazing systems tend to be negative. The positive values in cropping systems are due to both high P inputs from mineral fertilizers and high soil P-sorbing capacities. The negative values in grazing systems are a result of the removal of animal products without replacing the nutrients. Most of the N inputs in the crops grown in this region come from biological nitrogen fixation. The NUE in cropping systems is about 0.95, which is higher than the upper critical value of the desirable range (0.6–0.9). Given the high NUE value and the risk of soil mining, improving cropping systems NUE by adjusting the inputs to replenish N outputs and avoid soil erosion in the VRW are of considerable interest.