Spatial patterns of nutrients balance of major crops in Argentina

Argentina has a long tradition of agricultural systems that use few amounts of fertilizers. However, the crop nutrient balance remains unknown throughout the country. In this study, we estimated the nitrogen (N), phosphorus (P) and sulfur (S) balance at national and subnational scale of the six major grain crops: soybean, maize, wheat, sunflower, barley and sorghum. We found a negative spatio-temporal NPS balance with an annual average deficit of -22.4 kg ha(-1) year(-1) for N, -6.9 kg ha(-1) year(-1) for P and - 2.1 kg ha(-1) year(-1) for S. Considering the whole agricultural area analyzed, the balance represented a mean annual negative net outflow of 612 thousand tons (kT) of N, 166 kT of P and 58 kT of S. The nutrient balance was not homogeneous across the country, with significant differences among the three major productive regions: i) the Pampean nucleus region (-32.2, -8.5, -2.92 kg ha(-1) year(-1), for N, P and S respectively) ii) the non-nucleus Pampean region ( -14.3, -3.7, -2.03 kg ha(-1) year(-1) for N, P and S respectively), and iii) extra-Pampean region ( - 22.4, -6.3, -2.13 kg ha(-1) year(-1) for N, P and S respectively). Remarkably, despite having the highest N and P application rate, the Pampean nucleus region has the largest deficit of the analyzed nutrients. Soybean was the main driver of the nutrient mining in the country, accounting for 62 % of the NPS deficits at national scale ( -418 kT N year(-1) , 120 kT P year(-1) and -35 kT S year(-1)). Our findings suggest that the current fertilization practices applied to the major extensive crops in Argentina are far from being sufficient to supply the nutrients they demand, even cultivating soybean that is a N-fixing crop. These results highlight that Argentine main crops' high productivity is reached at the expense of soil nutrient depletion.

Automated summary

Argentina has a long tradition of using few fertilizers in agricultural systems, but the nutrient balance of crops in the country is still unknown. This study estimated the nitrogen, phosphorus, and sulfur balance of major grain crops at national and subnational scales and found a negative balance for all three nutrients. The nutrient balance varied across regions, with the most productive region having the largest deficit. Soybean cultivation was found to be the main driver of nutrient depletion in Argentina. The findings highlight the insufficiency of current fertilizer practices in supplying the nutrients demanded by major crops in the country.