Improving soil aggregation, aggregate‐associated C and N, and enzyme activities by green manure crops in the Loess Plateau of China

Abstract

Green manure and fertilization practices have substantial impacts on soil chemical and biological properties over time. A field experiment was conducted on Cumulic Haplustoll to investigate the effects of leguminous green manure (LGM) crops and nitrogen (N) fertilizer on dry‐stable soil aggregate distributions and stability, the concentrations of organic carbon (OC) and N in the bulk soil and separated aggregate fractions, and soil enzyme activities in dry croplands on the Loess Plateau of China. Species tested as LGM crops were Huai bean (Glycine ussuriensis Regel et Maack.), soybean (G. max (L.) Merr.) and mung bean (Phaseolus radiatus L.). Two rates of N fertilizer (0 and 162 kg N ha−1) applied to winter wheat sown after LGM was incorporated into surface soil. Results showed that the inclusion of LGM crops for 6 years significantly increased the total nitrogen (TN), soil organic carbon (SOC), aggregate‐associated N and OC concentrations, enhanced the values of aggregate content with >0.25 mm size (R0.25) and mean weight diameter (MWD), and boosted soil enzyme (invertase, urease, dehydrogenase and aryl‐sulfatase) activities at the 0–20‐cm depth compared to the bare fallow system under dryland conditions. The long‐term application of N fertilizer substantially increased the proportion of macroaggregates (>5.0 mm), MWD and N contents in the 0.25–5‐mm size aggregates, and promoted the relative activities of invertase, alkaline phosphatase, dehydrogenase and aryl‐sulphatase, but decreased the urease activity. The correlations among macroaggregate fractions and soil chemical properties, aggregate stability and enzyme activities were significant and positive; however, the correlations between small aggregate fractions (<2 mm) and corresponding parameters were negative, or there were no correlations. Overall, combining green manuring practices with suitable N fertilizer application should be recommended to improve the soil quality in dryland regions similar to the Loess Plateau of China. Highlights Green manure crops significantly increased soil enzyme activities, SOC and total N contents. Green manure crops increased macroaggregate (>5 mm) formation and stability. Application of N fertilizer significantly increased the proportions and stability of macroaggregates. Green manure crops along with N fertilizer helped to build better soil quality in a dry loess cropland.

Soil organic matter and clay zeta potential influence aggregation of a clayey red soil (Ultisol) under long-term fertilization

“…Application of amendments including manure and crop straws have been proven to be effective agricultural practices when attempting to improve soil aggregation and crop yields 1 . Pig manure has improved macroaggregate percentage and aggregate associated C and N content 5 , 6 . Soybean green manure improved large aggregates (> 2 mm) greater than a control treatment 5 .…”

“…Pig manure has improved macroaggregate percentage and aggregate associated C and N content 5 , 6 . Soybean green manure improved large aggregates (> 2 mm) greater than a control treatment 5 . Also, rice straw incorporation alone or in compound with NPK fertilizers was generally effective in increasing water-stable aggregation 1 , and restricting release of small particles (< 10 µm) of an Inceptisols, due to an increase in soil organic carbon (SOC) 7 .…”

Influence of Rice Husk Biochar and Compost Amendments on Salt Contents and Hydraulic Properties of Soil and Rice Yield in Salt-Affected Fields

“…It has been demonstrated that when organic matter such as animal manure, farm yard manure, or municipal wastes was applied to saline soils, sodium (Na + ) leaching can be accelerated through increasing soil porosity, hydraulic conductivity, and biopore networks, and reducing bulk density [15][16][17][18]. Furthermore, compost application can also decrease exchangeable sodium percentage (ESP) and increase water-holding capacity and aggregate stability [19,20]. In addition, organic matter application to saline soils may have positive effects on microbial biomass and enzymatic activities [21][22][23].…”

Ecological and Environmental Benefits of Planting Green Manure in Paddy Fields

“…In soil tectonics, infiltration is one of the main internal erosion processes, selectively eroding the fine particles that move through the voids formed by the coarser particles [14]. Green manure planting in high-latitude paddy fields can reduce soil consolidation caused by rainy seasons by increasing the content of water-stable aggregates and soil permeability [15], which is related to the soil colloid content caused by green manure root secretions and microbial enzyme activity [16]. Low-latitude rice fields are susceptible to water erosion caused by heavy rainfall during the winter season, and green manure varieties with a well-developed root system should be selected to protect the soil from nutrient loss in the topsoil.…”