Influencia del manejo del suelo en verano sobre la productividad y respuesta al N en el cultivo de trigo

From the year 2000, there has been a change in the national agricultural production, mainly driven by soybean cultivation, which as a result have the decrease of perennial pastures in rotations, also farmers began to implement direct sowing. The increase in the soybean-wheat sequence caused soil losses due to erosion and impoverishment of the level of nutrients in the soil. This added to the increase in wheat yield potential in the last 20 years, caused an increase in the need to add nitrogen via fertilizers. This work aims to evaluate the impact of the soybean crop's presence and level of productivity as a predecessor crop on the following wheat's productivity and nitrogen addition response. The experiment was carried out at the Estacion experimental Mario A. Cassinoni (EEMAC), Facultad de Agronomia, located in Paysandú. The soil is a Typical Eutric Brunosol belonging to the San Manuel unit. Sixteen treatments were carried out in combinations of the soybean predecessor (soybean up to V8, soybean up to R3, soybean at harvest population 50%, and soybean at harvest population 100%) and post-sowing nitrogen management of the wheat crop (RN at sowing, RN sowing - Z22, RN planting - Z30 and not limiting N). The hypotheses proposed were: i) the presence or the level of production of the soybean crop does not impact the productivity of the following crop and does not affect the availability of nitrogen in the soil when planting wheat; ii) nitrogen management cannot reverse the effect caused by the predecessor crop. During the experiment, the temperature and rainfall were similar to and well below the historical average, respectively. The predecessor crop affected the availability of nitrogen during wheat sowing. It also affected the final yield, being soybean up to R3, the one that caused the highest nitrogen in the soil (9,3 ppm), greater water availability at the time of wheat sowing wheat compared to the harvested predecessors (21% increase), and higher yield compared to the harvested predecessors (7434 vs 6175-6283 kg ha^-1). Moreover, nitrogen management influenced the final yield of the wheat crop. The maximum yield was reached when 88 kg de N ha^-1 were applied up to Z 22 (7179 kg ha^-1). On the other hand, the lowest yields were obtained with the RN treatments at sowing and non-limiting N, these being similar, despite having a difference in the added nitrogen of 210 kg N ha^-1. Different responses to the addition of nitrogen were detected depending on the predecessor, being soybean up to V8 the only one that increased yield when 233 kg N ha-1 (non-limiting N) were added, while in the remaining predecessors a yield penalty was observed when nitrogen was applied after Z 22. Moreover, the only nitrogen treatment that did not reach the industry required level of grain protein (11,5 %) was recommended nitrogen at sowing.