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, is collaborating with INPOFOS Southern Cone with support from AgroServicios Pampeanos, to establish a network of field experiments. The objectives are: 1) determine direct and residual responses to nitrogen (N), phosphorus (P), sulfur (S), and where indicated, potassium (K), magnesium (Mg), boron (B), copper (Cu), and zinc (Zn); 2) evaluate recommendation methods for N, P, and S fertilization; and 3) identify the level of deficiency and potential response to nutrients other than N, P, and S. The six fertilizer treatments are: 1) check, 2) PS, 3) NS, 4) NP, 5) NPS, and 6) NPS + KMgBCuZn. In 2004/05, five sites were planted to soybean within a corn-wheat/soybean rotation, and four sites to corn within a corn-soybean-wheat/soybean rotation.

Excellent climatic conditions allowed for high soybean yields in 2004. Soil testing indicated residual effects from P fertilization in previous years at all five sites. The average yield response to NPS across all five sites was 591 kg/ha, a 15% increase over the check. Significant yield responses were observed at 3 and 2 sites for P and S, respectively. Phosphorus responses were related to soil Bray-P levels, but S response did not relate to soil sulfate-S availability. Greater differences between treatments in 2004/05 than in 2001/02 indicates that full-season soybeans are responding to accumulated fertility in the P+S treatments.

Significant responses to N, P, and S were found at all four corn sites for 2004. The average yield response to NPS across sites was 4,629 kg/ha, a 64% increase over the check.
Each kg of applied N, P, and S contributed to 19, 45, and 61 kg of corn, respectively. Considering the four seasons of corn experiments, yield responses to N were related to soil nitrate-N availability (0 to 60 cm depth) and yields of 10,000 kg/ha could be reached with 177 kg/ha of available N at planting (soil N + fertilizer N). Similarly, low soil Bray P...less than 15 to 16 parts per million (ppm)...and low sulfate-S availability (less than 10 ppm, 0 to 20 cm depth) at planting were related to P and S response. No responses to nutrients other than N, P, and S were determined. Argentina-12