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, Argentina, has established a network of field experiments with the objectives of: 1) determining direct and residual responses to N, P and S, and where indicated, to K, Mg, B, Cu, and Zn); 2) evaluating recommendation methods for N, P and S fertilization; 3) identifying the level 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 2013-14, the two sites under corn-wheat/soybean (C-W/S) rotation were planted to wheat/double-cropped soybean, and the three sites under corn-soybean-wheat/soybean (C-S-W/S) rotation were planted to full-season soybean.

Adequate climatic conditions across both sites in a C-W/S rotation resulted in high wheat grain yields. Grain yield responses were significant to NPS+Micros at Balducchi, and to NP at San Alfredo. Responses to NPS averaged 3.2 t/ha (+163%) for both sites. Considering the 9 seasons with 40 sites under wheat, significant relationships were observed between Bray P-1 soil P concentrations and P responses, with critical P concentrations ranging between 19 and 26 ppm Bray 1-P. Below these critical levels, P responses are highly probable. Significant relationships were observed between wheat grain yields and soil N supply as predicted by soil nitrate-N concentrations, measured at sowing, plus the fertilizer N rate. When 140 kg N/ha was available at planting (soil + fertilizer N), wheat yields were approximately 4 t/ha. The response to S was not related to the pre-plant sulfate-S test (0 to 20 cm sample depth).

Excellent climatic conditions allowed for high yields in full season soybean and double-cropped soybean. Double-cropped soybean, planted after wheat, showed significant responses to NPS, and a yield average of 990 kg/ha (+35%). Full season soybean at the three C-S-W/S sites showed average responses to NPS of 720 kg/ha (+18%). Considering the 11 seasons with 62 sites under wheat, significant relationships were observed between Bray P-1 soil P concentrations and P responses, with critical P concentrations ranging between 12 and 14 ppm Bray 1-P. Significant relationships were observed between soybean grain yields and pre-plant sulfate-S test (0 to 20 cm sample depth).

For the 2014/15, sites will be cropped to corn under the C-W/S rotation, and under wheat/double cropped soybean in the C-S-W/S rotation.