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New Mexico State University (2021)

Cover Crops Affect Soil Health and Crop Production Under Limited-Irrigation Winter Wheat-Sorghum-Fallow

Thapa, Vesh Raj

Titre : Cover Crops Affect Soil Health and Crop Production Under Limited-Irrigation Winter Wheat-Sorghum-Fallow

Auteur : Thapa, Vesh Raj

Université de soutenance : New Mexico State University

Grade : Doctor of Philosophy (PhD) Plant and environment Science 2021

Résumé partiel
Cover crops are promoted to improve soil health and resilience by enhancing soil organic carbon (SOC) and nutrient cycling, yet the response of various cover crops on selected soil health indicators in semiarid cropping systems is not understood well. The objectives of this study were to (i) review the literature on how alternative management practices affect soil health in semiarid agroecosystems, (ii) evaluate the effects of various cover crops and their mixtures on soil microbial community structures and functions, (iii) evaluate the effects of various cover crops and their mixtures on soil organic matter (SOM) components and aggregate size distribution, and (iv) evaluate linkages between soil health, crop production, and cropping system resilience in a no-till winter wheat (Triticum aestivum L.)-sorghum (Sorghum bicolor L. Moench)- fallow/cover crop rotation with limited-irrigation management. A literature review included an overview of soil health principles and soil management practices for semiarid regions. Studies from the semiarid hot, dry, southern and central Great Plains (GP) suggest adoption of alternative management practices such as no-tillage or reduced tillage, cover cropping and diverse crop rotation, residue management, grassland restoration, and light or moderate livestock-grazing increases SOM fractions, enhances soil biology, and reduces soil erosion, thereby leading to improved soil health and resilience. Cover cropping is one of the strategies to improve soil health and resilience. Treatments for evaluating cover crop effects on soil health and resilience included pea (Pisum sativum L.), oat (Avena sativa L.), canola (Brassica napus L.), and mixtures of pea + oat (POmix), pea + canola (PCmix), pea + oat + canola (POCmix), and six-species mixture (SSmix) of pea + oat + canola + hairy vetch (Vicia villosa Roth) + forage radish (Raphanus sativus L.) + barley (Hordeum vulgare L.) as cover crops, and a fallow. Soil samples were collected in the summers of 2017-2020 from 0-15 cm depth of each plot established in fall 2015. Microbial community size and structure evaluated via ester-linked fatty acid methyl ester (EL-FAME) analysis during 2017-2018 showed total microbial community size and fungal abundance were similar between soils under oats and SSmix, and 31% and 41% greater than fallow, respectively.

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Page publiée le 3 décembre 2021