Efeito de braquiária e crotalária na produtividade da soja e do milho safrinha em solo com presença de fitonematoides

Abstract

The work was carried out with the objective of identifying crop succession and/or crop rotation systems that provide greater soybean and off-season corn yield, as well as a reduction in the population of nematodes in the soil. The research was carried out in Dourados, MS, during the 2019/20 and 2020/21 harvests. The experimental design was in randomized blocks with seven traits, in two implantation seasons: Summer 2019/20: 1) Brachiaria brizantha; 2) Brachiaria brizantha intercropped with Crotalaria ochroleuca; 3) C. ochroleuca; 4, 5, 6 and 7) soybean. 2020 Autumn-Winter: 1) Brachiaria brizantha; 2) C. ochroleuca; 3) off-season corn intercropped with Brachiaria ruziziensis; 4) off-season corn (control); 5) off-season corn intercropped with C. ochroleuca; 6) C. ochroleuca; 7) C. ochroleuca intercropped with Brachiaria ruziziensis. In the 2019/20 harvest, Crotalaria and Brachiaria were mowed together with the soybean harvest. In the autumn-winter 2020 harvest, Brachiaria was mowed together with the harvest of off-season corn. Soybean from the 2020/21 harvest and 2021 offseason corn were cultivated to evaluate the effect of the traits. Soybean was sown on October 18th 2020, with the DM66i68 IPRO cultivar, and off-season corn on February 20th 2021, with the hybrid MG30A37 PWU, both in total area. The collection of soybean soils and roots for nematode analysis was performed on October 23rd 2020, and at soybean flowering (R1) on January 8th, 2021. In soybean, the following traits were evaluated: plant height, stem dry mass, number of grains per pod, thousand seeds weight, number of grains per plant, yield, nematodes population per gram of root and population of nematodes per 200g of soil. In corn, the following were evaluated: plant height, number of ears per plant, number of grains per ear, thousand grains weight and yield. Data were submitted to analysis of variance to verify the effects of crop rotation or succession as a function of the implantation times and traits. Trait means were compared by the Tukey test at 5% of significance. Single Crotalaria ochroleuca cultivated in autumn-winter reduces the population density of Pratylenchus brachyurus but does not interfere with the population density of Rotylenchulus reniformis. Soybean has higher grain yield when cultivated in succession to Crotalaria ochroleuca intercropped with Brachiaria ruziziensis in autumn-winter. The off-season corn presents higher yield when the species are cultivated in the summer, but without the traits effect.