RESPUESTA DEL TRIGO A LA FERTILIZACIÓN NITROGENADA Y NITROAZUFRADA EN SUELOS ARENOSOS.

Numerous studies conducted on coarse-textured soils show, significant and positive wheat yield responses when soil nitrogen (N) availability is increased, and occasional positive yield responses to sulfur (S) additions. However, the available information is not consistent for the diagnosis and analysis of the marginal contribution of S on wheat grain responses in combination with N fertilization. Thus, the objective of this study was to quantify the yield response of dryland wheat crops to N and NS fertilization and to determine the relationship between yield response and several soil properties in sandy soils. The study consisted in 34 field experiments within the semiarid and subhumid sandy pampas region (Argentina) managed under no-tillage practices. Three treatments were evaluated: i) control (without fertilization), ii) 140 kg of N ha-1 [N-NO3 soil (0-40 cm) + N fertilizer], iii) 140 kg of N ha-1 [N-NO3 soil (0- 40 cm) + N fertilizer] + 12 kg of S ha-1. A positive response to N fertilization was observed in every experimental site. Mean grain yield response to the application of N was 949 kg ha-1. Although the mean grain yield response to S fertilization was 232 kg ha-1, only 38% of the sites (13 sites) showed a significant response to this treatment. Crop response to S fertilization was not related to soil organic matter (p = 0.61), sand content (p = 0.90), soil extractable S-S042-(p = 0.29), nor soil N-N03-(p = 0.47) levels. Furthermore, it decreased with increasing maximum grain yields and it was positively related to crop responses to N fertilization. We conclude that in coarse textured soils with significant N limitations, wheat responses to S fertilization are greater and more common in low productivity sites. [ABSTRACT FROM AUTHOR]