Effects of long-term green manure application on the content and structure of dissolved organic matter in red paddy soil

Abstract

Dissolved organic matter (DOM) plays important roles in soil biogeochemistry activity and nutrients transportation in soils, but studies regarding the long-term effects of green manures on the content and structure of DOM in red paddy soil have not been reported yet. A long-term green manure experiment established in 1982 was utilized to test the DOM contents in different treatments, and the spectral characteristics of DOM were investigated by using ultraviolet-visible (UV-Vis) spectrometry and Fourier transform infrared (FTIR) spectrometry. The experiment included four cropping systems: ricerice-milk vetch (RRV), rice-rice-rape (RRP), rice-rice-ryegrass (RRG) and rice-rice-winter fallow (RRF), among them, milk vetch, rape, and ryegrass are popular winter green manure species in southern China. The results showed that the content of dissolved organic carbon (DOC), which is widely used to estimate the concentration of DOM, was significantly promoted after the incorporation of green manures compared with the other sampling stages. The contents of aromatic groups and the degree of humification of DOM increased in RRV and RRP, suggesting more complex compositions of the soil DOM after long-term application of milk vetch and rape. The contents of phenol, alcohol and carboxylic acid group at the mature stage of early rice were significantly higher than those at the stage of after green manures turned over of green manures, especially for the RRV treatment. The absorption ratio of FTIR indicated that winter plantation of rape increased the aromatic-C/aliphatic-C ratio, and ryegrass increased the aromatic-C/carboxyl-C ratio. In conclusion, long-term planting

Keystone species affect the relationship between soil microbial diversity and ecosystem functioning under a subtropical land use change

“…6b, c). As noted previously, low rates of ammonium supply and alkaline soil in our study site could be a benefit for the AOB keystone species (Nitrosospira , Table S4) (Ke et al 2013;Gao et al 2018).…”

Designing Diversified Cropping Systems in China: Theory, Approaches and Implementation

“…In southern China, with abundant water and heat resources but typically hilly areas, legume or grass mulches as cover crops in hilly orchard and legume-based rotations are recommended to reduce continuous cropping and improve soil quality. For example, applying green manure e.g., Chinese milk vetch in rice field of subtropical China can enhance the quantity and quality of soil organic matter [76,77] . Overall, the region-specific design of crop diversification will aim to concurrently achieve safe, nutritious food production and environmental protection.…”

Effects of Organic Mulch on Soil Moisture and Nutrients in Karst Area of Southwest China

“…When Mulumba and Lal studied the effects of straw mulch on soil physical properties in Ohio, USA, it was found that the soil moisture content increased with the increase of straw mulch, but after more than 8 Mg ha -1 , the soil moisture did not increase significantly, so they thought 8 Mg ha -1 was the suitable mulching application rate [39]; when studying the effects of different straw mulch application rate on water storage and water conservation of spring maize field in the dryland area of North Wei River in China, it was considered that 9 Mg ha -1 was the appropriate straw mulch application rate for spring maize in the dryland of North Wei River and the similar ecological area in combination with the grain yield and water conservation benefits of straw mulch [40]; however, in this study, based on the short-term organic mulch experiment, it was found that the soil moisture content did not increase significantly when the straw mulch application rate exceeds 5.556 Mg ha -1 . Organic mulch and its decomposition products can improve soil structure and soil water infiltration rate by enhancing soil aggregate stability and increasing soil porosity [41][42][43], but it should be noted that the continuous increase of straw mulch may impart water repellent and hydrophobic properties to the soil surface and restrict water infiltration [44]. This further indicates that although straw mulch plays an important role in soil moisture conservation, there is not a simple positive proportional linear relationship between straw mulch application rate and soil moisture content.…”