Legume, cropping intensity, and N-fertilization effects on soil attributes and processes from an eight-year-old semiarid wheat system

Abstract

In the North American northern Great Plains (NGP), legumes are promising summer fallow replacement/cropping intensification options that may decrease dependence on nitrogen (N) fertilizer in small grain systems and mitigate effects of soil organic matter (SOM) losses from summer fallow. Benefits may not be realized immediately in semiarid conditions though, and longer-term effects of legumes and intensified cropping in this region are unclear, particularly in no-till systems. We compared effects of four no-till wheat (Triticum aestivum L.) cropping systems-summer fallow-wheat (F-W), continuous wheat (CW), legume green manure (pea, Pisum sativum L.)-wheat (LGM-W), and pea-wheat (P-W)-on select soil attributes in an 8-year-old rotation study, and N fertilizer effects on C and N mineralization on a duplicate soil set in a laboratory experiment. We analyzed potentially mineralizable carbon and nitrogen (PMC and PMN) and mineralization trends with a nonlinear model, microbial biomass carbon (MB-C), and wet aggregate stability (WAS). Legume-containing systems generally resulted in higher PMC, PMN, and MB-C, while intensified systems (CW and P-W) had higher WAS. Half-lives of PMC were shortest in intensified systems, and were longest in legume systems (LGM-W and P-W) for PMN. Nitrogen addition depressed C and N mineralization, particularly in CW, and generally shortened the half-life of mineralizable C. Legumes may increase long-term, no-till NGP agroecosystem resilience and sustainability by (1) increasing the available N-supply (*26-50 %) compared to wheatonly systems, thereby reducing the need for N fertilizer for subsequent crops, and (2) by potentially mitigating negative effects of SOM loss from summer fallow.

Six years of different tillage systems affected aggregate-associated SOM in a semi-arid loam soil from Central Iran

“…Including a legume species with fast decomposing residue and the ability to fix atmospheric N 2 in the cropping sequence and practices as a cover crop enhances soil N storage with sustaining nutrient availability and soil fertility in semi-arid regions (Raiesi, 2007;O'Dea et al, 2015). The mean N sequestration over 6 years was also correlated with tillage years, explaining 82% of the variability in N sequestration (N pool = 0.210 Â year + 1.42, R 2 = 0.82, P < 0.1).…”

The Role of Legumes in Plant Community Succession of Degraded Grasslands in Northern China

“…and Oxytropis aciphylla Ledeb., Table S4). Legume species could not only enrich soil nutrient but also mitigate soil organic matter loss and increase potentially mineralizable carbon and nitrogen (O'Dea et al, 2015) and cumulative C mineralization (Biederbeck et al, 2005). Legume species could also restore soil microbial communities by increasing the biomass, activity and functional diversity of soil microbial community, and soil enzyme activity (Biederbeck et al, 2005;Li et al, 2012a).…”

Cover Crop Management in Semi‐Arid Regions: Effect on Soil and Cash Crop

“…Several longer-term studies suggest that N benefits to wheat may be realized only after multiple years of legumes in rotation (Campbell et al, 1992;Allen et al, 2011), especially in no-till systems (Schoenau & Campbell, 1996). O'Dea et al (2015 found potentially mineralizable N after four cycles of pulse cover crop alternating annually with wheat was 1.5 times that found in fallow-wheat systems.…”