Legume-grass mixtures increase forage yield by improving soil quality in different ecological regions of the Qinghai-Tibet Plateau

Abstract

IntroductionInformation on the relationship between soil quality and forage yield of legume-grass mixtures in different ecological regions can guide decision-making to achieve eco-friendly and sustainable pasture production. This study’s objective was to assess the effects of different cropping systems on soil physical properties, nitrogen fractions, enzyme activities, and forage yield and determine suitable legume-grass mixtures for different ecoregions.MethodsOats (Avena sativa L.), forage peas (Pisum sativum L.), common vetch (Vicia sativa L.), and fava beans (Vicia faba L.) were grown in monocultures and mixtures (YS: oats and forage peas; YJ: oats and common vetch; YC: oats and fava beans) in three ecological regions (HZ: Huangshui Valley; GN: Sanjiangyuan District; MY: Qilian Mountains Basin) in a split-plot design.ResultsThe results showed that the forage yield decreased with increasing altitude, with an order of GN (3203 m a.s.l.; YH 8.89 t·ha-1) < HZ (2661 m; YH 9.38 t·ha-1) < MY (2513m; YH 9.78 t·ha-1). Meanwhile, the forage yield was higher for mixed crops than for single crops in all ecological regions. In the 0-10 cm soil layer, the contents of total nitrogen (TN), microbial biomass nitrogen (MBN), soil organic matter (SOM), soluble organic nitrogen (SON), urease (UE), nitrate reductase (NR), sucrase (SC), and bacterial community alpha diversity, as well as relative abundance of dominant bacteria, were higher for mixed crops than for oats unicast. In addition, soil physical properties, nitrogen fractions, and enzyme activities varied in a wider range in the 0-10 cm soil layer than in the 10-20 cm layer, with larger values in the surface layer than in the subsurface layer. MBN, SON, UE, SC and catalase (CAT) were significantly and positively correlated with forage yield (P < 0.05). Ammonium nitrogen (ANN), nitrate nitrogen (NN), SOM and cropping systems (R) were significantly and positively correlated with Shannon and bacterial community (P < 0.05). The highest yields in the three ecological regions were 13.00 t·ha-1 for YS in MY, 10.59 t·ha-1 for YC in GN, and 10.63 t·ha-1 for YS in HZ.DiscussionWe recommend planting oats and forage peas in the Qilian Mountains Basin, oats and fava beans in the Sanjiangyuan District, and oats and forage peas in Huangshui valley. Our results provide new insights into eco-friendly, sustainable, and cost-effective forage production in the Qinghai Alpine Region in China.

Soil microbial community are more sensitive to ecological regions than cropping systems in alpine annual grassland of the Qinghai-Tibet Plateau

“…This was contrary to the findings of Zhu et al (2020) who concluded that soil bacterial diversity was higher at lower elevations and suggested that this pattern was related to higher vegetation diversity at lower elevations. This result may have been due to differences in climatic conditions within specific altitudinal zones (Press, 2009), differences in sensitivity of soil bacteria and fungi to the environment, or differences in the initial microbial communities in different ecological zones (Luo et al, 2023). In addition, soil fungal and bacterial α-diversity in the same cropping pattern differed significantly across ecological zones.…”

“…( 4) Soil bacteria and fungi differ in their sensitivity to the environment. Due to the different adaptability of crops to the environment, differences in the biological nitrogen fixation capacity of leguminous crops in different ecological regions leads to differences in soil nitrogen cycling and utilization, indirectly affecting the diversity of soil microorganisms (Luo et al, 2023).…”

“…However, soil microbes are sensitive to environmental and crop responses (Brockett et al, 2012). Microbial activity and microbial biomass increase when a mixture of grass and legume crops is sown because the soil is so closely linked to the microbial community as it provides an ideal environment for bacteria, fungi, and a myriad of other organisms to survive (Luo et al, 2023). Plant diversity affects soil environmental conditions, with increased belowground biomass and root activity having significant effects on soil properties and soil secretions.…”

Legume–grass mixtures improve biological nitrogen fixation and nitrogen transfer by promoting nodulation and altering root conformation in different ecological regions of the Qinghai–Tibet Plateau

“…Biological nitrogen fixation (BNF) by legumes is an important way to replenish soil nitrogen ( Yao et al., 2019 ). Mixed grass and legume forage cropping systems, which significantly optimize the cropping system by increasing plant diversity and improving soil health ( Crème et al., 2015 ; Zhao et al., 2015 ), are a way to develop sustainable ecological agriculture ( Luo et al., 2023 ).…”