Implication of Urochloa spp. Intercropping and Conservation Agriculture on Soil Microbiological Quality and Yield of Tahiti Acid Lime in Long Term Orchard Experiment

Techniques such as intercropping and minimum tillage improve soil quality, including soil microbial activity, which stimulates the efficient use of soil resources by plants. However, the effects of such practices in soil under citrus orchards have not been well characterized. In this study, we aimed to determine the effects of mowing and intercrop species on soil microbiological characteristics beneath a Tahiti acid lime orchard. The orchard was planted using minimum tillage and intercropped with two species of Urochloa species ( U. ruziziensis —ruzi grass; U. decumbens —signal grass), with two types of mowers for Urochloa biomass (ecological; conventional) and herbicide applications. The study was conducted over 10 years. The ecological mower made the largest deposition of the intercrop biomass, thus providing the lowest disturbance of soil microbial activity and increasing, on average over all 10 years, the basal soil respiration (45%), microbial biomass carbon (25%), abundance of 16S rRNA (1.5%) and ITS (3.5%) genes, and arbuscular mycorrhizal fungi (30%), and providing a ca. 20% higher fruit yield. U. ruziziensis in combination with ecological mowing stimulated the abundance of the genes nif H (1.5%) and pho D (3.0%). The herbicide showed little influence. We conclude that the use of U. ruziziensis as an intercrop in citrus orchards subjected to ecological mowing can be recommended for improving and sustaining soil quality and citrus fruit production.