Looking for Sustainability: Long-Term Fertilization in the Pampas of Argentina.

Soils of the Pampas of Argentina were originally highly fertile, but cultivation and soil mixing decreased soil organic matter (SOM), and nutrient budgets are still quite negative with removal exceeding applications of nitrogen (N), phosphorus (P), and sulfur (S), the three generally deficient nutrients in the region. Fertilization management focuses on the immediate crop but there is no information on its long-term effects. A long-term fertilization study was established in 2000 at five farmer’s fields of the CREA Region Southern Santa Fe in a collaborative project of CREA, a farmer’s association, the International Plant Nutrition Institute (IPNI), and ASP, a fertilizer company. Treatments consist into four nutrient combinations (PS, NS, NP, and NPS) and a Check treatment. Sites are under maize-wheat/double cropped soybean or maize-full season soybean-wheat/double cropped soybean rotations. Initial soil fertility level, previous cropping history, rotation, and yield levels determined site-specific responses, efficiencies and economic performances. Balanced fertilization with N, P, and S increased grain yields by 42-129%, 35-192%, 7-38% and 6-61%, averages of both rotations, for maize, wheat, full-season soybean, and double cropped soybean, respectively. Differences between the NPS and Check treatments have increased over the years due to improved and depleted soil fertility in the NPS and Check treatments, respectively. Effects of balanced NPS fertilization were observed in increased soil test P (STP) levels, SOM concentrations, and soil microbial activity; but soil pH tended to decrease. The NPS treatment was also the most profitable, except in cases with high initial STP level, where the NS treatment was the best option. Overall, these results highlight the impact of fertilization management under a reposition criterion on agronomic, environmental and economic aspects in the central Pampas of Argentina.