Soil physical disturbance reduces maize growth, nutrition, and mycorrhiza formation in a green manure rotation with vetch

Abstract

Green manure crops such as vetch (Vicia sativa L.) and their association with plant growth-promoting microorganisms like arbuscular mycorrhizal fungi (AMF) and diazotrophic bacteria are known to improve soil fertility and crop nutrition in agroecosystems. In a greenhouse pot experiment with a fully factorial design, we investigated the effects of green manure with vetch (incorporated or cut leaving the soil undisturbed), soil disturbance simulating a tillage event (without and with) and mineral fertilization (without and with NPK) on the abundance of available soil nutrients (NO3−, NH4+ and HPO42−), maize growth and nutrient content (N and P), and maize mycorrhiza formation by native AMF. First vetch was grown for 10 weeks and then left to mineralize for 12 weeks incorporated or not into the soil. Then before maize sowing, another soil-disturbance event was performed (with and without) and finally maize was grown for 18 weeks without and with NPK fertilization. Main results showed that the amount of soil NO3− and HPO42− increased substantially after the green manure mineralization before maize sowing, though with lower values after green manure soil incorporation, compared to that of the treatment without soil incorporation. Green manure soil incorporation reduced the final total maize dry weight biomass without NPK fertilization, but when combined with NPK green manure soil incorporation resulted in the highest final total maize dry weight biomass. However, type of green manure management had no effects on the other maize plant variables measured nor AMF root colonization. On the contrary, soil disturbance before maize sowing resulted in decreased AMF root colonization, cob dry weight, and cob N and P content. In conclusion, our results show that soil physical disturbance caused alterations in the plant-microbe-soil dynamics in the present vetch-maize rotation resulting in reduced maize growth, nutrition, and mycorrhiza formation.