Long-term organic fertilizer substitution increases rice yield by improving soil properties and regulating soil bacteria

The cultivation of green manure or rice straw returns in southern China increases crop yields and soil fertility. Few studies have reported the effects of combining both management techniques on rice performance and soil fertility. A 3-year field study was carried out to analyse the impacts of the co-incorporation practice on soil microbial and biochemical parameters as well as crop yield. Five treatments were tested: (i) no-fertilizer (CK); (ii) chemical fertilizer (F); (iii) F plus green manure (FM); (iv) F plus rice straw (FS); (v) F plus green manure plus rice straw (FMS). The results showed that incorporation of green manure and/or rice straw increased double rice yields by 4.1% (FM), 4.7% (FS) and 9.6% (FMS) compared with F. The FMS treatment enhanced soil organic C (SOC), total N (TN), mineral N (Nₘᵢₙ), and available K (AK) levels by combining the advantage of FM in increasing TN and Nₘᵢₙ and the advantage of FS in increasing SOC and AK in comparison with F. The incorporation of green manure and/or rice straw stimulated microbial growth (total phospholipid fatty acids, PLFAs) and altered the soil microbial community structure relative to F, in which FMS had the greatest effect. The enzyme activities of β-glucosidase, β-cellobiosidase, N-acetyl-glucosaminidase, L-leucine aminopeptidase and phosphatase were higher in the green manure and/or rice straw application treatments than in the F treatment in the order FM ≈ FS < FMS. The partial least squares path model (PLS-PM) analysis indicated that green manure mainly influenced the abovementioned indices in the early rice season, while the effects of rice straw lasted until the late rice season. Our results suggest that co-incorporation of green manure and rice straw is a more effective practice for improving soil fertility and rice yields.

Co-incorporation of green manure and rice straw improves rice production, soil chemical, biochemical and microbiological properties in a typical paddy field in southern China

Soil carbon and nitrogen are essential factors for agricultural production and climate changes. A total of 106 soil samples from three agricultural lands (including two rice fields and one sugarcane field) and four non-agricultural lands (including two forest lands, one wasteland and one built-up land) in the Mun River Basin were collected to determine soil carbon, nitrogen, soil pH, soil particle sizes and explore the influence of pH and soil texture on soil C and N. The results show that total organic carbon (TOC) and nitrogen (TON) contents in topsoil (TOC: 2.78 ~ 18.83 g kg-1; TON: 0.48 ~ 2.05 g kg-1) are much higher than those in deep soil (TOC: 0.35 ~ 6.08 g kg-1; TON: <0.99 g kg-1). In topsoil, their contents of forest lands and croplands (TOC: average 15.37 g kg-1; TON: average 1.29 g kg-1) are higher than those of other land uses (TOC: average 5.28 g kg-1; TON: average 0.38 g kg-1). The pH values range from 4.2 to 6.1 in topsoil, and with increase in soil depth, they tend to increase and then decrease. Soil carbon, nitrogen and the C/N (TC/TN ratio) are negatively correlated with soil pH, demonstrating that relatively low pH benefits the accumulation of organic matter. Most soil samples are considered as sandy loam and silt loam from the percentages of clay, silt and sand. For soil profiles below 50 cm, the TOC and TON average contents of soil samples which contain more clay and silt are higher than those of other soil samples.

/pdf/effects-of-soil-ph-and-texture-on-soil-carbon-and-nitrogen-1ayqbfr2g1.pdf

Effects of soil pH and texture on soil carbon and nitrogen in soil profiles under different land uses in Mun River Basin, Northeast Thailand.

The stronger impact of inorganic nitrogen fertilization on soil bacterial community than organic fertilization in short-term condition

Long-term straw mulching with nitrogen fertilization increases nutrient and microbial determinants of soil quality in a maize–wheat rotation on China's Loess Plateau

Soil C/N and pH together as a comprehensive indicator for evaluating the effects of organic substitution management in subtropical paddy fields after application of high-quality amendments

Substitution of chemical fertilizers with organic amendments recycle organic wastes and minimizes adverse environmental effects of mineral-fertilizer overuse. In China, cropping systems which utilize two rice plantings per year are the most important planting pattern for ensuring food security. To date, few studies have comprehensively evaluated the responses of soil fertility and rice performance in double rice cropping systems to the partial substitution of chemical nitrogen (N) with organic N under the same input rates of N, P and K. In addition, the influences of the mineral-to-organic substitution ratio and season on these responses remain poorly understood. Here, a 34-year field fertilizer trial was sampled to determine the impacts of organic substitution regime and growing season on soil biochemical properties and rice yield. Compared with the mineral NPK fertilizer regime, the replacement of 30 %, 50 % and 70 % of total N with organic N increased the yield of early rice by 4.5 %–8.3 %, respectively and that of late rice by 6.7 %–9.6 %. Moreover, the organic substitution regimes significantly improved soil biochemical indicators. The higher organic N substitution percentage resulted in higher values of many soil properties with the exception of TC:TN, fungi:bacteria and G+:G−, which tended to decrease with increasing substitution. Both fertilizer regime and growing season affected soil nutrient contents, enzyme activity and microbial community structure. The relative abundances of identified PLFA biomarkers 16:1ω5c, 16:1ω7c and 18:1ω7c were markedly higher (p ≤ 0.05) in the organic alternative treated soils than the NPK-treated soils in both seasons. Our results suggest that the substitution of 70 % chemical N with organic N is the most effective fertilizer practice for improving soil fertility and rice yield in double rice cropping systems.

Partial substitution of chemical nitrogen with organic nitrogen improves rice yield, soil biochemical indictors and microbial composition in a double rice cropping system in south China

Free-living nitrogen fixation (FLNF) by diazotrophs is a ubiquitous renewable resource and may constitute an attractive viable solution to the problem of environmental degradation caused by nitrogen over-fertilization. However, the biotic and abiotic control mechanisms of free-living nitrogen fixation are poorly understood. Moreover, there is rare information to link the composition and functions of diazotrophic communities; additionally, there are insufficient or inadequate predictors of the potential N fixation rate (PNFR) to help improve fertilization strategies. Here, through high-throughput sequencing, network analysis, and 15N2 labelling methods, we investigated the long-term effects of partial substitution of mineral N by organic fertilizers on diazotroph abundance and composition in double rice cropping systems. The field trial was conducted for 34 years and included five treatments: control without fertilizer (CK); only mineral NPK fertilizer (NPK); 70% inorganic N + 30% organic N + PK (NPKM1); 50% inorganic N + 50% organic N + PK (NPKM2); 30% inorganic N + 70% organic N + PK (NPKM3). Our results revealed that at the same nutrient input level, increasing the percentage of organic N substitution reduced diazotrophic abundance. Compared with the CK and NPK treatments, the organic substitution regimes reduced the fluctuation range of the PNFR between the early and late rice growing seasons. NH4+-N was the primary factor that negatively correlated (p

Predicting the influence of fertilization regimes on potential N fixation through their effect on free-living diazotrophic community structure in double rice cropping systems

Long-term mineral fertilizer substitution by organic fertilizer and the effect on the abundance and community structure of ammonia-oxidizing archaea and bacteria in paddy soil of south China

Guangrong Liu

Papers

Soil C/N and pH together as a comprehensive indicator for evaluating the effects of organic substitution management in subtropical paddy fields after application of high-quality amendments

Partial substitution of chemical nitrogen with organic nitrogen improves rice yield, soil biochemical indictors and microbial composition in a double rice cropping system in south China

Predicting the influence of fertilization regimes on potential N fixation through their effect on free-living diazotrophic community structure in double rice cropping systems

Long-term mineral fertilizer substitution by organic fertilizer and the effect on the abundance and community structure of ammonia-oxidizing archaea and bacteria in paddy soil of south China