Establishing a Plant Nutrition Network for the CREA Region in Southern Santa Fé

The Regional Consortium of Agricultural Experimentation (CREA), a farmers' organization based in Southern Santa Fe, has established a network of field experiments with the objectives of: 1) determining direct and residual responses to N, P, S, and where indicated, to K, Mg, B, Cu, and Zn), 2) evaluating recommendation methods for N, P and S fertilization, 3) identifying the degree of deficiency and potential response to nutrients other than N, P and S, and 4) evaluating the evolution of soil quality under contrasting nutrient management practices. In 2014/15, the two sites under corn-wheat/soybean (C-W/S) rotation were planted to corn, and the three sites under corn-soybean-wheat/soybean (C-S-W/S) rotation were planted to wheat/soybean.

Adequate climatic conditions across the five sites resulted in high grain yields in all three crops. Corn grain yield responses were significant to NS and to P at Balducchi, and to NPS at San Alfredo. Responses to NPS averaged 5.6 t/ha (+75%) for both sites. Wheat grain yield responses were significant to applications of N and P at La Hansa and to N, P, and S at La Blanca and Lambare. Average grain yield response to NPS at the three sites was 2,290 kg/ha (+86%). Response to other nutrients (K, Mg, B, Cu, and Zn) was significant only at Lambare. Double-cropped soybean, planted after wheat, reached record yields and showed significant responses to NPS, an average yield response of 1,545 kg/ha (+49%). Responses to N were related to available N at planting (soil + fertilizer N) for corn and wheat. Corn yields of 10 to 12 t/ha might be reached with 144 to 271 kg N/ha; while wheat yields of 4 t/ha would be reached with 140 kg N/ha. Significant relationships were observed between Bray P-1 soil P concentrations and P responses, with critical P concentrations ranging between 11 and 19 ppm Bray P-1 for the three crops. Below these critical levels, P responses are highly probable. Responses to S were related to pre-plant soil sulfate-S test (0-20 cm), with a critical level of 10 ppm for corn and double-cropped soybean.

For the 2015/16, sites will be cropped to wheat/double cropped soybean under the C-W/S rotation, and to corn under the C-S-W/S rotation.