Cover crops affect the partial nitrogen balance in a maize-forage cropping system

Abstract

Part of the nitrogen (N) fertilizer applied to crops is lost to the environment, contributing to global warming, eutrophication, and groundwater contamination. However, low N supply stimulates soil organic N turnover and carbon (C) loss, since the soil N/C ratio in soil is quasiconstant, ultimately resulting in land degradation. Grasses such as ruzigrass (Urochloa ruziziensis) grown as winter pasture or a cover crop in rotation with maize (Zea mays) can reduce N leaching, however, this may induce N deficiency and depress yields in the subsequent maize crop. Despite the potential to decrease N loss, this rotation may negatively affect the overall N balance of the cropping system. However, this remains poorly quantified. To test this hypothesis, maize, fertilized with zero to 210 kg N ha -1 , was grown after ruzigrass, palisade grass (Urochloa brizanta) and Guinea grass (Pannicum maximum), and the N inputs, outputs and partial N balance determined. Despite the intrinsically poor soil quality associated with the tropical Ultisol, maize grown after the grasses was efficient in acquiring N, resulting in a negative N balance even when 210 kg ha -1 of N was applied after Guinea grass. Losses by leaching, N2O emission and NH3 volatilization did not exceed 13.8 kg ha -1 irrespective of the grass type. Despite a similar N loss among grasses, Guinea grass resulted in a higher N export in the maize grain due to a higher yield, resulting in a more negative N balance. Soil N depletion can lead to C loss, which can result in land degradation.

Urochloa in Tropical Agroecosystems

“…Considering that the mean N accumulation among Urochloa species is about 100 kg N ha −1 (Table 2), up to 42 kg N ha −1 could be added into the soil from BNF. Urochloa and Panicum grasses used as cover crops in rotation under N-limited conditions help to prevent N leaching (Rocha et al, 2020a) and its associated BNF may substantially contributed to part of the N-demand of the subsequent maize culture (Rocha et al, 2020a,b).…”

Maize and sorghum root growth and yield when intercropped with forage grasses

“…The benefits of nitrogen fixation by sunn hemp for crop rotations have been well documented (Bertin et al., 2005). Legumes increase soil nitrogen availability (Rocha et al., 2020), especially in sandy soils with a low organic matter content (Masvaya et al., 2017). The total amount of nitrogen and the carbon/nitrogen ratio of plant residues from forages can influence the supply of nitrogen to the system and its availability to the maize crop, affecting grain production (Rosolem et al., 2004).…”

“…), and ruzigrass [ Urochloa ruziziensis (Germ. & Evrard) Crins] produce large amounts of dry matter (DM) and have vigorous and deep root systems that increase drought tolerance and nutrient cycling and reduce leaching losses (Almeida et al., 2018; Calonego & Rosolem, 2010; Garcia et al., 2008; Rocha et al., 2020; Rosolem et al., 2017). Palisade grass can improve soil physical characteristics in compacted layers at depths greater than 0.1 m (Stumpf et al., 2016), and the high density of the fine roots produced by palisade grass decreases the potential for nitrate leaching by increasing the complexity of the soil pore network (Galdos et al., 2020).…”

Cover crops and controlled-release urea decrease nitrogen mobility and improve nitrogen stock in a tropical sandy soil with cotton cultivation

“…Use of cover crops is a common technique to improve N efficiency, and its use has shown benefits for various crop systems (Rosolem et al, 2018;Momesso et al, 2019;Rocha et al, 2019;Rocha et al, 2020;Galdos et al, 2020). In some cases, the use of grass with a high carbon-to-nitrogen ratio (C:N) causes N immobilization due to the use of N available in the soil by microorganisms, which decompose the straw; this momentarily reduces the availability of N in the subsequent crop (Momesso et al, 2019;Rocha et al, 2019;Silva et al, 2020).…”