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 2012-13, all five remaining sites of the network were planted to corn, with two sites under corn-wheat/soybean (C-W/S) rotation and three sites under corn-soybean-wheat/soybean (C-S-W/S) rotation.

Contrasting climatic conditions across sites resulted in variable grain yields. Grain yield responses to NPS were significant at Balducchi and La Hansa sites; to NS at San Alfredo, Lambaré, and La Blanca sites; and to NP at San Alfredo and Lambaré sites. Responses to NPS averaged 5.4 t/ha (+102%) and 6.4 t/ha (+109%) for C-W/S and C-S-W/S rotations, respectively. There were no significant responses to nutrients other than NPS. Considering the 13 seasons with 45 sites under corn, 38 sites under wheat, 57 sites under full-season and double cropped soybean, significant relationships were observed between Bray P-1 soil P concentrations and P responses, with critical P concentrations ranging between 12 and 20 ppm for the three crops. Below these critical levels, P responses are highly probable. Significant relationships were observed between grain yields of corn and soil N supply as predicted by soil nitrate-N concentrations measured at sowing plus the fertilizer N rate. When 270 to 280 kg N/ha was available at planting (soil + fertilizer N), corn yields were approximately 12 t/ha. A high probability to S response in corn has been determined for sites when the pre-plant sulfate-S test (0 to 20 cm) had concentrations less than 10 mg/kg. The analysis of the first 13 years of the nutrition network has shown that adequate NPS management increased grain yields, contributed to improved water use efficiency, tended to increase soil organic matter, decreased soil pH, and allowed for soil P build-up. During the 2013-14 season, three sites will be planted to full season soybean (C-S-W/S rotation) and two sites to wheat/double cropped soybean (C-W/S rotation).