Application of two vermicomposts on a Rice crop: Effects on soil biological properties and rice quality and yield
Vermicomposts have been considered as a soil additive to reduce the use of mineral fertilizers because they provide required nutrients, increase cation exchange capacity, and improve water-holding capacity. However, the effect of each vermicompost on soil properties and crop yield depends on its chemical composition. The main objective of this work was to study the effect of incorporating two vermicomposts of different chemical nature (cow dung, CD; and green forages, GF) at rates of 3 and 6 t C ha–1, respectively, on soil biological properties (soil microbial biomass, soil respiration and soil enzymatic activities), soil humus–enzymes complexes, nutrition (N, P, and K plant contents, pigments, and leaf soluble carbohydrate concentrations), and yield parameters of rice (Oryza sativa cv. Puntal) over 3 yr on an Aquic Xerofluvent located near Seville, Spain. Vermicomposts had a positive effect on the soil biological properties and rice quality and yield parameters with respect to the no-vermicompost-amended soil, although at the end of the experimental period and at the high organic matter rate, the soil microbial biomass and dehydrogenase, urease, β-glucosidase, phosphatase, and arylsulfatase activities increased more in the CD-amended soils compared with the GF-amended soils (20.8, 12.8, 16.9, 17.6, 15.3, and 15.1%, respectively). However, the results obtained in the soil humus-enzymes complexes indicate that the highest values were found in the GF- compared with CD-amended soils. This increase in soil biological properties produced an increase in the plant nutrition, which increased rice quality and yield. The application of CD increased the grain protein concentration (5.6%), the grain starch concentration (7.8%), the percentage of full grains (3.1%), and the rice yield (7.9%) compared with the GF-amended soils. These results suggest that the chemical composition of the two vermicomposts influenced the soil biological properties, and therefore in the rice yield parameters. For both vermicomposts, the application of CD originated an increase in the soil biological properties and also in the rice yield parameters than did application of GF.