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

The Regional Consortium of Agricultural Experimentation (CREA), a farmer 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 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. In 2009/10, two sites within a corn-wheat/soybean (C-W/S) rotation were planted to wheat/soybean, and four sites within a corn-soybean-wheat/soybean (C-S-W/S) rotation were planted to corn.

Excellent climatic conditions at the four corn experiments allowed for high yields. Yield responses to N, P, and/or S were significant at all sites (average of 4,737 kg/ha), and responses to nutrients other than NPS were significant at one site. Wheat experiments were differently affected by drought and frosts. However, responses to NP were significant at both sites (average of 2,152 kg/ha, +212%). Excellent climatic conditions contributed to high yields of doublecropped soybean, with average responses to N, P, and S of 329, 944, and 476 kg/ha. Considering the 10 seasons with 38 sites under corn, 33 sites under wheat, and 42 sites under doublecropped soybean, significant relationships were established between Bray 1 P and P responses, with critical levels between 12 and 20 ppm for the three crops below which P responses are highly probable. Also, significant relationships were established between grain yield and soil N supply as predicted by soil nitrate-N measured at sowing + fertilizer N rate, for corn and wheat.

The analysis of the first 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, allowed for soil P build-up, and increased profits. Sites will be planted to corn in the C-W/S rotation and to wheat/soybean in the C-S-W/S rotation during the 2010/11 season. Argentina-12