Maize growth and soil nitrogen availability after fertilization with cattle manure and/or gliricidia in semi-arid NE Brazil

Cattle manure is used as fertilizer by farmers in northeastern Brazil. However, the manure is insufficient to fertilize all cropping areas and is usually of low quality and may immobilize N. The use of Gliricidia sepium as green manure could increase the amount and quality of organic fertilizers. However, the high-quality biomass of this legume is valued as forage and may also decompose too quickly and cause nitrogen (N) leaching. This study aimed to identify efficient management practices for cattle manure and Gliricidia to improve N uptake and crop productivity in semi-arid NE Brazil. For this, we conducted three experiments. In the greenhouse, we evaluated maize growth and N uptake after application of Gliricidia and/or cattle manure under different soil moisture conditions. A litterbag field experiment evaluated the decomposition dynamics of Gliricidia or manure. Finally, a field experiment tested the effects of mixing and/or splitting Gliricidia and manure on maize productivity and N uptake. In the greenhouse, maize dry matter production and N uptake and apparent N recovery from fertilizers were significantly greater in treatments with higher proportions of Gliricidia, but mainly under high soil moisture conditions. The litterbag experiment showed that Gliricidia indeed decomposed twice as fast as cattle manure, that decomposition was up to 2.5 times faster when the materials were incorporated rather than surface applied, and also that N release was more synchronized to maize demand when fertilizers were split in two applications. In the field experiment, we observed that both mixing cattle manure and Gliricidia and splitting the application in two increased in maize productivity up to 350%.