Hai-Ming Tang

Effects of winter cover crops straws incorporation on CH4 and N2O emission from double-cropping paddy fields in southern China.

Residue management in cropping systems is believed to improve soil quality. However, the effects of residue management on methane (CH4) and nitrous oxide (N2O) emissions from paddy field in Southern China have not been well researched. The emissions of CH4 and N2O were investigated in double cropping rice (Oryza sativa L.) systems with straw returning of different winter cover crops by using the static chamber-gas chromatography technique. A randomized block experiment with three replications was established in 2004 in Hunan Province, China, including rice–rice–ryegrass (Lolium multiflorum L.) (Ry-R-R), rice–rice–Chinese milk vetch (Astragalus sinicus L.) (Mv-R-R) and rice–rice with winter fallow (Fa-R-R). The results showed that straw returning of winter crops significantly increased the CH4 emission during both rice growing seasons when compared with Fa-R-R. Ry-R-R plots had the largest CH4 emissions during the early rice growing season with 14.235 and 15.906 g m−2 in 2012 and 2013, respectively, when Ry-R-R plots had the largest CH4 emission during the later rice growing season with 35.673 and 38.606 g m−2 in 2012 and 2013, respectively. The Ry-R-R and Mv-R-R also had larger N2O emissions than Fa-R-R in both rice seasons. When compared to Fa-R-R, total N2O emissions in the early rice growing season were increased by 0.05 g m−2 in Ry-R-R and 0.063 g m−2 in Mv-R-R in 2012, and by 0.058 g m−2 in Ry-R-R and 0.068 g m−2 in Mv-R-R in 2013, respectively. Similar result were obtained in the late rice growing season, and the total N2O emissions were increased by 0.104 g m−2 in Ry-R-R and 0.073 g m−2 in Mv-R-R in 2012, and by 0.108 g m−2 in Ry-R-R and 0.076 g m−2 in Mv-R-R in 2013, respectively. The global warming potentials (GWPs) from paddy fields were ranked as Ry-R-R>Mv-R-R>Fa-R-R. As a result, straw returning of winter cover crops has significant effects on increase of CH4 and N2O emission from paddy field in double cropping rice system.

Effects of Chinese Milk Vetch (Astragalus sinicus L.) Residue Incorporation on CH4 and N2O Emission from a Double-Rice Paddy Soil

Abstract Methane (CH4) and nitrous oxide (N2O) emissions from paddy soils have seldom been estimated when leguminous green manure is applied as a nitrogen source. In this paper, gas fluxes were measured by using a pot sampling device combined with a static chamber method to estimate the effects of Chinese milk vetch (Astragalus sinicus L., CMV) on CH4 and N2O emissions and their integrated global warming potentials (GWP) in a double-rice cropping system. Four treatments (no nitrogen fertilizer, NF; urea as chemical fertilizer, CF; CMV incorporation, MV; 50% CMV incorporation and 50% urea, MVCF) were established. CH4 flux peaked on the 15th d after treatment application. Total season CH4 emission was increased by MV and MVCF by 370 and 209%, 152 and 66%, when compared with NF and CF, respectively. Most of the increased CH4 was emitted in the first two months after incorporation of CMV. N2O emission from CF was 17- and 5.6-fold higher than that from MV and MVCF, respectively. Application of CMV restricted N2O emission caused by the application of urea. Improved CMV residue management was needed to minify CH4 emission induced by the input of organic material. Despite the highest GWP being found in MV, we recommend CMV, when applied as an N source in paddy fields, as a potential mitigation tool for greenhouse gas emissions.

Effects of Straw Recycling of Winter Covering Crop on Methane and Nitrous Oxide Emissions in Paddy Field

Abstract The emissions of methane (CH4) and nitrous oxide (N2O) were determined in double rice (Oryza sativa L.) cropping systems with different winter covering crops using the static chamber-gas chromatography technique to assess the effects of different covering crops on the emissions of greenhouse gases. Four cropping systems with different covering corps after double rice seasons, i.e., ryegrass with no-tillage (T1), Chinese milk vetch with no-tillage (T2), rape seed with tillage (T3), and potato with straw mulching and tillage (T4), were compared with the winter fallow after double rice seasons (CK). The results showed that straw recycling of winter crops significantly increased the emission of CH4 during both rice growing seasons compared to CK. Treatments T4 and T1 had the largest CH4 emissions during the early rice growing season with 20.713 and 16.068 g m−2, respectively, and the T4 and T3 had the largest CH4 emission during the later rice growing season with 60.421 and 48.666 g m−2, respectively. The 4 treatments with winter covering crops also had larger N2O emissions than CK in both rice seasons. Compared to the N2O emission in CK, the emissions of the gas increased by 265% in T1, 320% in T2, 275% in T3, and 65% in T4 during the growth of early rice, and by 158% in T1, 113% in T2, 134% in T3, and 42% in T4 during the growth of late rice. The global warming potentials from paddy fields were ranked as T4 > T3 > T1 > T2 > CK. As a result, straw recycling of winter covering crops has significant effects on increase of CH4 and N2O emission from paddy field in double rice cropping system.

Impact of long-term fertilization practices on the soil aggregation and humic substances under double-cropped rice fields

Soil organic matter (SOM) content and soil aggregation are essential components of soil structure, which plays an important role in soil quality and fertility. Also, the SOM content, aggregation, and humus substances in paddy field were affected by application of fertilization practices. However, there is still limited information about the effects of long-term different fertilization practices on soil aggregation and carbon content in the humic acid (C-HAF), fulvic acid (C-FAF), and humin (C-HUM) fractions under double-cropping rice (Oryza sativa L.) system in Southern China paddy fields. Therefore, the effects of long-term fertilizer application on soil aggregation and C-HUM, C-HAF, and C-FAF contents in 0–5-, 5–10-, and 10–20-cm soil depth under double-cropped rice fields in Southern China were investigated. The experiment located at NingXiang County in Hunan Province, China begins in 1986 and the experiment includes five treatments: without fertilizer input (CK), mineral fertilizer alone (MF), rice straw residues and mineral fertilizer (RF), 30% organic matter and 70% mineral fertilizer (LOM), and 60% organic matter and 40% mineral fertilizer (HOM). The results showed that the soil total organic carbon content in paddy soils with RF, LOM, and HOM treatments was significant higher (P < 0.05) than that of the CK treatment at early and late rice maturity stages. The different sizes of soil aggregates with different fertilization treatments were decreased as HOM > LOM > RF > MF > CK. The HOM treatment had the highest percentage of soil aggregates in each size class and the CK treatment had the lowest percentage of soil aggregates in each size class in 0–5-, 5–10-, and 10–20-cm soil depth at early and late rice maturity stages. The soil C-HAF, C-FAF, and C-HUM contents were increased by long-term combined application of manure with mineral fertilizer practices. Meanwhile, the results indicated that the soil C-HAF, C-FAF, and C-HUM contents with RF, LOM, and HOM treatments were significantly higher (P < 0.05) than that of the CK treatment at early and late rice maturity stages. As a result, the soil total organic carbon content, each size class of soil aggregates, and soil C-HAF, C-FAF, and C-HUM contents were increased by long-term combined application of manure with mineral fertilizer in double-cropped rice fields.

Long-term effects of NPK fertilizers and organic manures on soil organic carbon and carbon management index under a double-cropping rice system in Southern China

ABSTRACT The effects of manure and chemical fertilizer on soil bulk density, soil organic carbon (SOC), and the role of carbon management index (CMI) in soil quality evaluation were studied under a double-cropping rice system in a long-term experiment. The experiment included five fertilizer treatments: without fertilizer input (CK), chemical fertilizer alone (MF), rice straw residue plus chemical fertilizer (RF), 30% organic matter plus 70% chemical fertilizer (LOM), and 60% organic matter plus 40% chemical fertilizer (HOM). RF, LOM, HOM treatments increased SOC content relative to MF treatment in the paddy fields at 0–20 cm. RF, LOM, HOM treatments were more effective for increasing CMI, lability index, lability of C, and SOC stocks, as compared with MF treatment. Based on rice grain yield and carbon storage, integrated fertilization of chemical fertilizer and organic manure proved to be the most effective practices for improving crop productivity and SOC sequestration.

Dynamic Change of Soil Enzyme Activities and Soil Microbe During Rice Main Growth Stages in Different Long-term Fertilizer Regimes

Soil microbe and soil enzyme activities are closely related to the fertilizer inputs. Our objective was to explore the dynamic change of soil microbe and soil enzyme activities in paddy field during early and late rice (Oryza sativa L.) main growth stages with different long-term fertilizer managements in the double cropping rice system. we analyzed the soil microbe and soil enzyme activities with mineral fertilizer alone (MF), rice residues and mineral fertilizer (RF), 30% organic matter and 70% mineral fertilizer (LOM), 60% organic matter and 40% mineral fertilizer (HOM), and without fertilizer (CK) basis on long-term fertilizer experiment. The results showed that the soil enzyme activities were increased by application of mineral fertilizer along with manure or rice residues at the main growth stages of early and late rice. The soil urease activities for different fertilizer managements was RF>HOM>LOM>MF>CK at the main growth stages of early and late rice. The soil catalase activities with HOM, LOM treatments was highest, and was significantly higher than that of RF, MF, CK treatments at the main growth stages of rice. The soil invertase and dehydrogenase activities with HOM treatment were highest, and were significantly higher than that of CK at the main growth stages of rice. And the soil cellobiohyrolase activities with RF treatment were highest, and were significantly higher than that of MF, CK treatments at the main growth stages of rice. Meanwhile, the results indicated that different fertilization managements were significantly affected some physiological function soil microbial quantity. The amount of nitrifying and denitrification bacteria in soil for different fertilizer managements was HOM>LOM>RF>MF>CK at the main growth stages of early and late rice. Meanwhile, the amount of ammonifiers and cellulose”decomposing bacteria in soil for different fertilizer managements was MF>RF>LOM>HOM>CK and LOM>RF>MF>HOM>CK at the main growth stages of rice, respectively. The amount of azotobacteria in soil with RF treatment was highest, and was significantly higher than that of MF, CK treatments at the main growth stages of rice. As a result, the soil microbe and soil enzyme activities were increased by applied of fertilizer practices, the effect of mineral fertilizer combined with manure or rice residues is better than that of only mineral fertilizer.

Effects of winter cover crop straw recycling on soil organic carbon and soil carbon pool management index in paddy fields: Effects of winter cover crop straw recycling on soil organic carbon and soil carbon pool management index in paddy fields

Research on total organic carbon(TOC),carbon pool activivty(CPA) and carbon pool management index(CPMI) of paddy fields with different double cropping rice patterns could enhance the exploitation of winter cover crop and the assessment of paddy rice cropping patterns.This paper discussed soil TOC,CPA and CPMI in double cropping rice systems with straw recycling of different winter cover crops.Experiments were conducted in field plot trials of ryegrass and double cropping rice(T1),Chinese milk vetch and double cropping rice(T2),rape and double cropping rice(T3) and fallow and double cropping rice(CK).The results showed that recycling of winter cover crop straws significantly increased soil TOC and CPA over CK.The order of TOC content and CPA under different cropping patterns was T2 T1 T3 CK at the early and later rice harvest stages.Compared with CK,T1,T2 and T3 averagely increased soil TOC content respectively by 6.73%,10.53% and 4.79% at early rice harvest in 2011 and 2012 and by 4.16%,6.20% and 2.37% at later rice harvest in 2011 and 2012.However,no significant difference existed in TOC content among T1,T2 and T3 treatments.The CPA under treatments T1 and T2 with winter cover crop straw recycling was also higher than that of CK.Compared with CK,CPA under treatments T1 and T2 on average increased respectively by 10.52% and 21.52% at early rice harvest and by 11.99% and 15.59% at later rice harvest in 2011 and 2012.Also compared with CK,CPA,activity index(AI),carbon pool index(CPI) and CPMI under treatments T1,T2 and T3 improved at early and later rice harvest stages.The results further showed that CPA,AI,CPI and CPMI increased with winter cover crop straw recycling.The order of CPA,AI,CPI and CPMI under the different cropping patterns were T2 T1 T3 CK.Thus winter cover crop straw recycling significantly influenced TOC content,AC and CPMI in paddy fields.Winter cover crop straw recycling had the best effect with Chinese milk vetch,followed by ryegrass and then rape.