Assessing the potential of a Trichoderma-based compost activator to hasten the decomposition of incorporated rice straw

The potential for a Trichoderma-based compost activator was tested for in-situ rice straw decomposition, under both laboratory and field conditions. Inoculation of Trichoderma caused a 50% reduction in the indigenous fungal population after 2 weeks of incubation for both laboratory and field experiments. However, the Trichoderma population declined during the latter part of the incubation. Despite the significant reduction in fungal population during the first 2 weeks of incubation, inoculated samples were found to have higher indigenous and total fungal population at the end of the experiments with as much as a 300% increase in the laboratory experiment and 50% during day-21 and day-28 samplings in the field experiment. The laboratory incubation experiment revealed that inoculated samples released an average of 16% higher amounts of CO2 compared to uninoculated straw in sterile soil samples. Unsterile soil inoculated with Trichoderma released the highest amount of CO2 in the laboratory experiment. In the field experiment, improved decomposition was observed in samples inoculated with Trichoderma and placed below ground (WTBG). From the initial value of around 35%, the C content in WTBG was down to 28.63% after 42 days of incubation and was the lowest among treatments. This is significantly lower compared with NTBG (No Trichoderma placed below ground, 31.1% C), WTSS (With Trichoderma placed on soil surface, 33.83% C), and NTSS (No Trichoderma placed on soil surface, 34.30% carbon). The WTBG treatment also had the highest N content of 1.1%. The C:N ratio of WTBG was only 26.27, 39.51% lower than the C:N ratio of NTBG, which is 43.43. These results prove that the Trichoderma-based inoculant has the potential to hasten the decomposition of incorporated rice straw.

Effects of the Autumn Incorporation of Rice Straw and Application of Lime Nitrogen on Methane and Nitrous Oxide Emissions and Rice Growth of a High-Yielding Paddy Field in a Cool-Temperate Region in Japan

The effects of autumn plowing and lime nitrogen application on rice straw decomposition, CH4 and N2O emission and rice growth in the following year in a high-yielding rice cultivated paddy field were evaluated for two years. The experimental plots were set up, combining different times of rice straw (750 g m−2) incorporation into the soil by plowing (autumn or the following spring), with and without lime nitrogen application in autumn (5 g-N m−2). Autumn plowing promoted the decomposition of rice straw, but the application of lime nitrogen did not show a consistent trend. The soil pH was high (7.3) at the studied site, and the alkaline effect of lime nitrogen may not have been significant. As with straw decomposition, CH4 emissions were suppressed by autumn plowing, and no effect from the lime nitrogen application was observed. It was also suggested that the straw decomposition period may be shorter and the CH4 emissions may be higher in high-yielding cultivars that require a longer ripening period than in normal cultivars. The effect of both treatments on N2O emission was not clear. Both the autumn plowing of rice straw and lime nitrogen application were effective in promoting rice growth and increasing rice yield.

Effect of Cover Crops Associated With Lettuce Production Under No-Tillage System

The use of cover crops has benefits for the chemical, physical and biological properties of the soil. However, together with the need for good vegetable productivity, considerable challenges arise in several regions of Brazil. The preparation of conventional soil for initiating no-tillage systems is necessary to create a management history and assimilate the benefits of the no-tillage system in vegetables, ensuring sustainable production. The objective of this research was to evaluate lettuce yield as a function of different cover crops as a function of resistance to soil penetration. The experiment was conducted in the horticulture sector of the University of Rio Verde, Rio Verde, Goiás, Brazil. The cover crops used were sunflower (Helianthus annuus), sunn hemp (Crotalaria juncea), and fallow, and the vegetable used was lettuce (Lactuca sativa). The variables analyzed were plant height and lettuce yield, straw decomposition, and soil resistance to penetration. The collected data were submitted to analysis of variance, and if significant, was compared by Tukey test (p < 0.05) and regression analysis. The lettuce height in the different management systems showed no statistical differences. The decomposition of the straw presented accentuated degradation for the evaluated cover crops and the productivity was bigger in the straw of crotalaria and fallow. Soil resistance for cover crops was not greater than 2 MPa.

Urea Application Rate for Crop Straw Decomposition in Temperate China

Returning straw to the field has become the most important straw utilization method in China. The aim of this research was to study the appropriate amount of nitrogen fertilizer applied when returning the straw of three major crops (wheat, rice, and corn) to the field in areas under low to high yield levels based on the demand of nitrogen for microbial decomposition of straw. Under the condition of returning 100% straw to the field, we developed the formula for calculating the nitrogen application rate and estimated the urea application rate for the three major grain crops. The results showed that returning straws of wheat, early-season rice, middle-season rice and late-season rice, and corn to the field with urea application at the rate of about 150 kg/ha, 120～135 kg/ha, 75 kg/ha, and 75～90 kg/ha, respectively, can provide sufficient nitrogen for microbial decomposition. The urea application rate for returning 100% wheat straw to the field in Huang-Huai-Hai region, Middle-Lower Yangtze region, Loess plateau region, and Northwest arid region was 135–230 kg/ha, 110–190 kg/ha, 85–145 kg/ha, and 95–165 kg/ha, respectively. 52.5–98.5 kg/ha of urea was used for 100% early rice straw returning to the field in Middle-Lower Yangtze region and South China. In addition, the urea application rate for 100% middle-late rice straw returning to the field was 95–180 kg/ha, 100–185 kg/ha, 95–175 kg/ha, and 75–140 kg/ha, respectively. The rate of urea application for 100% corn straw returning to the field in Northeast China, Huang-Huai-Hai, Northwest arid region, and Southwest China was 60–135 kg/ha, 50–115 kg/ha, 60–135 kg/ha, and 45–105 kg/ha, respectively. The amount of nitrogen fertilizer required for the total return of crop straw is not only affected by crop straw C : N, yield per unit area, and ratio of grass to grain but also affected by straw returning mode, regional nitrogen application level, and other factors. Therefore, the amount of nitrogen fertilizer should be adjusted according to the type of cropping system, soil, and climatic conditions of the specific location. This substantial N input for stimulating straw decomposition may favor N losses with nitrate leaching and nitrous oxide emissions and hold a potential for soil N eutrophication in the long term if the level is not carefully adjusted to the N requirement of the subsequent crops and changes in soil organic matter levels.

Water-Covered Depth with the Freeze–Thaw Cycle Influences Fungal Communities on Rice Straw Decomposition

Rice is a staple food for the world’s population. However, the straw produced by rice cultivation is not used sufficiently. Returning rice straw to the field is an effective way to help reduce labor and protect the soil. This study focused on the effect of water-covered depth with the freeze–thaw cycle on rice straw decomposition and the soil fungal community structure in a field in Northeast China. The field and controlled experiments were designed, and the fungal ITS1 region was tested by high-throughput sequencing for analyzing the fungal communities in this study. The results showed that water coverage with the freeze–thaw cycle promoted the decomposition of rice straw and influenced the fungal community structure; by analyzing the network of the fungal communities, it was found that the potential keystone taxa were Penicillium, Talaromyces, Fusarium, and Aspergillus in straw decomposition; and the strains with high beta-glucosidase, carboxymethyl cellulase, laccase, lignin peroxidase, and manganese peroxidase could also be isolated in the treated experiment. Furthermore, plant pathogenic fungi were found to decrease in the water-covered treatment. We hope that our results can help in rice production and straw return in practice.

Effects of different returning method combined with decomposer on decomposition of organic components of straw and soil fertility

In view of the problems of low straw decomposition rates and reduced soil fertility in southern Liaoning, China, we investigated the effects of no-tillage mode (NT), deep loosening + deep rotary tillage mode (PT), rotary tillage mode (RT) and the addition of decomposing agent (the next is called a decomposer) (NT + S, PT + S, RT + S) on the decomposition proportion of straw, respectively, by using the nylon net bag method in combination with 365-day field plot experiments. The decomposition rules of cellulose, hemicellulose and lignin as well as the dynamics of soil organic carbon (SOC), soil microbial biomass carbon (MBC) and soil dissolved organic carbon (DOC) in straw returned to the field for 15, 35, 55, 75, 95, 145 and 365 days were analyzed. The results showed that in the short term, the decomposition of straw was better in both the rotray tillage and deep loosening + deep rotary modes than in the no-tillage mode, and the addition of decomposer significantly promoted the decomposition of straw and the release of carbon from straw, among them, the RT + S treatment had the highest straw decomposition proportion and carbon release proportion in all sampling periods. After a one year experimental cycle, the RT + S treatment showed the highest proportion of cellulose, hemicellulose and lignin decomposition with 35.49%, 84.23% and 85.50%, respectively, and soil SOC, MBC and DOC contents were also higher than the other treatments with an increase of 2.30 g kg−1, 14.22 mg kg−1 and 25.10 mg kg−1, respectively, compared to the pre-experimental soil. Our results show that in the short term, to accelerate the decomposition rate of returned straw and increase the content of various forms of carbon in soil, rotary tillage can be used to return the straw to the field, while also spraying straw decomposer on its surface. This experiment used a new straw decomposer rich in a variety of microorganisms, combined with the comparison of a variety of straw return modes, and in-depth study of straw decomposition effects of cellulose, hemicellulose and lignin. Thus, a scheme that can effectively improve the decomposition rate of straw and the content of various forms of organic carbon in soil within a short period of time was explored to provide theoretical support for the southern Liaoning.

Decomposition Characteristics, Nutrient Release and Structural Changes of Maize Straw in Dryland Farming under Combined Application of Animal Manure

Straw and animal manure are major organic waste materials from agricultural ecosystems. Different kinds of animal manure combined with straw (AM-S) may have varying effects on the decomposition, nutrient release, and structural changes of maize straw. Using the Humic Cambisols soil as the experimental area, the straw decomposition characteristics under the co-application of animal manure were studied following the nylon net bag landfill method. The experiment involved four treatments: maize straw only (S), maize straw plus ox manure (SO), maize straw plus chicken manure (SC), and maize straw plus pig manure (SP). The treatments with AM-S accelerated the decomposition of straw and increased the release rate of nutrients and organic components (cellulose, hemicellulose, and lignin). During the 240 days of the study, straw decomposition showed a trend of increasing rapidly in the first stages and then increasing slowly in the latter stages in all the treatments. At 240 d, the straw decomposition rates and carbon release rates of the AM-S treatments were 65.25–71.87% and 64.04–69.35%, respectively. At the end of the experiment, the order for the final release rates of nitrogen (N), phosphorus (P), and potassium (K) was K (93.25–96.56%) > P (42.25–55.08%) > N (40.01–52.23%). Moreover, scanning electron microscopy showed that SP treatment had the highest degree of structural changes of the maize straw compared with the other treatments. The purpose of this study was to screen the effective animal manure that can promote straw decomposition and provide a reference for the rational use of straw and animal manure management. In conclusion, the study suggested that the co-application of animal manure and straw should be adopted in agricultural systems, especially SP treatment, as it was more conducive to promoting the decomposition of maize straw and the release of nutrients.