Practices sustaining soil organic matter and rice yield in a tropical monsoon region

ABSTRACT

Sandy soils are usually dominant in tropical monsoon regions, due to the high weathering potential associated with high temperatures and precipitation. The organic matter content of sandy soils is low due to low clay content and high microbial activity. Therefore, soil management practices that alter the soil organic carbon (SOC) content may be important for the sustainable management of crop yields. Thus, the present study investigates the distribution of rice yield and SOC content under different land management practices and analyzes the relationship between rice yield and SOC with pertinent management practices (manure and fertilizer applications). The soil horizons from 0- to 40-cm depths were collected in each layer to measure SOC and soil properties at 64 sites. At each sampling site, farmers were given questionnaires and the record book for the standards for good agricultural practices of farm owners were gathered to assimilate information on rice yield and their practices during 2010–2014. The mean rice yield of the whole crop year and SOC were 2.93 Mg ha^?1 and 47.09 Mg C ha^?1, respectively, in the irrigated areas, and were 2.38 Mg ha^?1 and 32.08 Mg C ha^?1 in the rain-fed areas. Significantly higher values were obtained in the irrigated areas (p < 0.05). There was a significant positive correlation between rice yield and SOC in both the irrigated areas (R² = 0.72, p < 0.01) and the rain-fed areas (R² = 0.85, p < 0.01); however, the slopes of these regression equations were significantly different. In both irrigated and rain-fed areas, manure should be applied every year, with an optimal application rate of N, P, and K fertilizers being selected. The combination of manure, fertilizer, and increasing irrigation facilities the maintenance of SOC levels and substantially increases rice yields.     

Use of the RothC model to estimate the carbon sequestration potential of organic matter application in Japanese arable soils

Abstract

We estimated the carbon (C) sequestration potential of organic matter application in Japanese arable soils at a country scale by applying the Rothamsted carbon (RothC) model at a 1-km resolution. After establishing the baseline soil organic carbon (SOC) content for 1990, a 25-year simulation was run for four management scenarios: A (minimum organic matter application), B (farmyard manure application), C (double cropping for paddy fields) and D (both B and C). The total SOC decreased during the simulation in all four scenarios because the C input in all four scenarios was lower than that required to maintain the baseline 1990 SOC level. Scenario A resulted in the greatest depletion, reflecting the effects of increased organic matter application in the other scenarios. The 25-year difference in SOC accumulation between scenario A and scenarios B, C and D was 32.3, 11.1 and 43.4?Mt?C, respectively. The annual SOC accumulation per unit area was similar to a previous estimate, and the 25-year averages were 0.30, 0.10 and 0.41?t?C?ha^?1?year^?1 for scenarios B, C and D, respectively. The system we developed in the present study, that is, linking the RothC model and soil spatial data, can be useful for estimating the potential C sequestration resulting from an increase in organic matter input to Japanese arable soils, although more feasible scenarios need to be developed to enable more realistic estimation.     

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

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.     

Short-term responses of soil nutrients and corn yield to tillage and organic amendment

Field experiments were conducted in 2010 and 2011 at the Agricultural College of Shiraz University to evaluate the effects of cattle manure and nitrogen (N) fertilizers on soil properties such as soil organic carbon (SOC), soil organic nitrogen (SON), soil electrical conductivity, soil pH and corn yield under two tillage systems. Treatments included tillage systems in two levels as conventional tillage and reduced tillage as subplots, cattle manure (0, 25 and 50 tons ha^?1) and N fertilizer (0, 125 and 250 kg N ha^?1) as sub-subplots. Results showed that SOC and SON were significantly affected by tillage system in both years of the experiment. SOC and SON were higher in reduced tillage compared to conventional tillage. Tillage system had no significant effect on grain yield, plant height and 1000 seed weight. Increased cattle manure rates at 25 and 50 tons ha^?1 increased grain yield by 27% and 38%, respectively, in 2010 and 25% and 25% in 2011. The results showed that application of cattle manure combined with N fertilizer might be an efficient management to increase soil productivity in southern Iran, in soils with poor organic content. Additionally, reduced tillage showed to be an efficient method to increase soil organic matter.     

Changes in soil carbon stock under the wheat-based cropping systems at Vojvodina province of Serbia

The aim of this study was to assess the changes in soil organic carbon (SOC) stock in relation to the carbon (C) input from nine wheat-based cropping systems and untilled grass. The SOC pool ranged from 32.1 to 49.4 Mg ha^?1 at 0–20 cm and from 94 to 171 Mg ha^?1 at 0–100 cm for the arable soil, while in untilled grassland, it was higher (54 and 185 Mg C ha^?1, respectively). SOC stock was observed to be lower at the unfertilized 2-year rotation and higher at the 4-year rotation with manure and mineral fertilization. The study showed a winter wheat yield decrease of 176.8 kg ha^?1 for a 1- Mg ha^?1 SOC stock change in the 0–20-cm soil depth. The estimated C input for SOC stock maintenance was from 266 to 340 g C m^?2 year^?1 for winter wheat and rotations, respectively. Additional C input did not increase the SOC pool, suggesting that arable plots had a limited ability to increase SOC. These results provide guidance for the selection of management practices to improve C sequestration.     

Modeling a long-term effect of rice straw incorporation on SOC content and grain yield in rice field

ABSTRACT

The long-term effects of rice straw incorporation on soil organic carbon (SOC) content and rice yield were evaluated from rice cultivation with different treatments: no rice straw (control), rice straw (RS), and rice straw compost (RSC) as a main-plots; five levels of nitrogen (N) fertilizer application: 0, 100, 150, 200, and 250 of N (kg ha^?1) as a sub-plots. The denitrification and decomposition (DNDC) model was employed to simulate changes in SOC content and rice grain yield over 35 years. Additionally, scenario analysis on continuous or discontinuous RS incorporation in rice fields was conducted using the DNDC model. The long-term results indicated that RS and RSC treatments played a crucial role in increasing grain yields by 9% and 11% due to the increased SOC contents compared to control treatment. The validated DNDC model on SOC contents and yields showed a good agreement between the observed and simulated values based on the normalized root mean square errors. The model predicted a rapid decline of SOC contents without RS incorporation. Results suggested that incorporating rice straw or amending manure to paddy soils is a preferred practice for maintaining SOC contents.     

LONG‐TERM MANURING AND FERTILIZER EFFECTS ON DEPLETION OF SOIL ORGANIC CARBON STOCKS UNDER PEARL MILLET‐CLUSTER BEAN‐CASTOR ROTATION IN WESTERN INDIA

Soil organic carbon (SOC) pools are important for maintaining soil productivity and reducing the net CO₂ loading of the atmosphere. An 18‐year old long‐term field experiment involving pearl millet‐cluster bean‐castor sequence was conducted on an Entisol in western India to examine the effects of chemical fertilizers and manuring on carbon pools in relation to crop productivity and C sequestration. The data showed that even the addition of 33.5 Mg ha⁻¹ C inputs through crop residues as well as farm yard manure could not compensate the SOC depletion by oxidation and resulted in the net loss of 4.4 Mg C ha⁻¹ in 18 years. The loss of SOC stock in the control was 12 Mg C ha⁻¹. Conjunctive use of chemical fertilizers along with farm yard manure produced higher agronomic yields and reduced the rate of SOC depletion. The higher average seed yields of pearl millet (809 kg ha⁻¹), cluster bean (576), and castor (827) over six cropping seasons were obtained through integrated use of fertilizers and manure. For every Mg increase in profile SOC stock, there was an overall increase of 0.46 Mg of crop yield, comprising increase in individual yield of pearl millet (0.17 Mg ha⁻¹ y⁻¹ Mg⁻¹ SOC), cluster bean (0.14) and castor (0.15). The magnitude of SOC build up was proportional to the C inputs. Carbon pools were significantly correlated with SOC, which increased with application of organic amendments. Threshold C input of 3.3 Mg C ha⁻¹ y⁻¹ was needed to maintain the SOC stock even at the low antecedent level. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of Applied Cattle Manure on Winter Wheat (Triticum aestivum L.) Grain Yield,Soil pH and Soil Organic Carbon

ABSTRACT

Animal manure is used in crop production to improve crop yield and soil properties. The impact of cattle manure applied in one year on yield and soil properties in the subsequent years has not been extensively studied. This work evaluated the effect of manure application on winter wheat grain yield (Triticum aestivum L.), soil organic carbon (SOC), and soil pH. Cattle manure was applied once every four years at a rate of 267 kg N ha^?1. Grain yield and soil samples (0–15 cm) were collected annually from the Magruder Plots, Oklahoma. Soil samples were analyzed using a glass electrode (pH) and LECO dry combustion analyzer (SOC). The highest yield (2.8 Mg ha^?1) occurred in the second year after manure application. Yield in the second year exceeded yield in the first year by 66%. Yields in the third and fourth year were similar to yields in the other years. No changes in soil pH and SOC were observed in each of the four years that constituted the manure application cycle. Cattle manure (267 kg N ha^?1) could be applied once to serve a four-year period without major yield differences while also improving soil pH and SOC when compared to the check.     

Effect of organic and inorganic sources of nutrients on soil microbial activity and soil organic carbon build-up under rice in west coast of India

The effect of medium-term (5 years) application of organic and inorganic sources of nutrients (as mineral or inorganic fertilizers) on soil organic carbon (SOC), SOC stock, carbon (C) build-up rate, microbial and enzyme activities in flooded rice soils was tested in west coast of India. Compared to the application of vermicompost, glyricidia (Glyricidia maculate) (fresh) and eupatorium (Chromolaena adenophorum) (fresh) and dhaincha (Sesbania rostrata) (fresh), the application of farmyard manure (FYM) and combined application of paddy straw (dry) and water hyacinth (PsWh) (fresh) improved the SOC content significantly (p < 0.05). The lowest (p < 0.05) SOC content (0.81%) was observed in untreated control. The highest (p < 0.05) SOC stock (23.7 Mg C ha^?1) was observed in FYM-treated plots followed by recommended dose of mineral fertilizer (RDF) (23.2 Mg C ha^?1) and it was lowest (16.5 Mg C ha^?1) in untreated control. Soil microbial biomass carbon (C_mb) (246 µg g^?1 soil) and C_mb/SOC (1.92%) were highest (p < 0.05) in FYM-treated plot. The highest (p < 0.05) value of metabolic quotient (qCO₂) was recorded under RDF (19.7 µg CO₂-C g^?1 C_mb h^?1) and untreated control (19.6 µg CO₂-C g^?1 C_mb h^?1). Application of organic and inorganic sources of nutrients impacted soil enzyme activities significantly (p < 0.05) with FYM causing highest dehydrogenase (20.5 µg TPF g^?1 day^?1), phosphatase (659 µg PNP g^?1 h^?1) and urease (0.29 µg urea g^?1 h^?1) activities. Application of organic source of nutrients especially FYM improved the microbial and enzyme activities in flooded and transplanted rice soils. Although the grain yield was higher with the application of RDF, but the use of FYM as an organic agricultural practice is more useful when efforts are intended to conserve more SOC and improved microbial activity.     

种植绿肥与稻秸协同还田对单季稻田土壤有机碳库和酶活性的影响

种植绿肥和秸秆还田是稻田土壤培肥的重要措施。研究江汉平原单季稻田冬闲期种植绿肥及稻秸不同利用模式对土壤有机碳库和土壤酶活性的影响,为合理利用秸秆和土地资源提供科学依据。该研究基于3 a田间定位试验,以稻秸不还田不种绿肥(CK1)和不施肥空白(CK0)为对照,分析了冬闲期稻秸全量覆盖单独还田(RSM)、稻秸原位焚烧还田(RSB)、单种绿肥(GM)以及稻秸全量覆盖与种植绿肥协同还田利用(RSM+GM)等处理模式下土壤有机碳各组分含量、碳库管理指数、酶活性的变化及其与水稻产量的关系。结果表明:与CK1和CK0相比,RSB处理3 a后显著降低了土壤稳态有机碳含量,对土壤总有机碳、活性有机碳含量以及碳库管理指数均无显著影响;而GM、RSM及RSM+GM处理3a后显著提高了土壤活性有机碳含量、碳库指数、碳库活度、碳库活度指数和碳库管理指数,尤其是RSM和RSM+GM处理还可显著提高土壤总有机碳含量,且多数指标均以RSM+GM处理增幅为最大,其次是RSM处理。与CK1相比,RSB处理3a后显著提高了过氧化氢酶和蔗糖酶活性,但对土壤脲酶活性无显著影响;而RSM、GM及RSM+GM处理模式3 a后均可显著增加土壤过氧化氢酶、脲酶和蔗糖酶活性,其中RSM+GM处理模式在1 a后即可显著提高土壤脲酶活性,2 a后显著提高土壤过氧化氢酶和蔗糖酶活性,3 a后土壤过氧化氢酶和蔗糖酶活性增幅均是最大。相比于CK1,RSM和RSB处理模式3 a的稻谷增产效果均不显著,而GM和RSM+GM处理模式连续3 a显著提高了稻谷产量,增幅分别为6.88%～11.67%和6.00%～13.40%。相关性分析表明,土壤总有机碳、活性有机碳、碳库管理指数、土壤酶活性与水稻产量之间均呈极显著正相关关系。综上,在江汉平原单季稻作条件下,冬闲期稻秸全量覆盖还田或种植绿肥均可改善土壤肥力,增加作物产量,但前者更有助于土壤有机碳积累,后者更利于作物产量提升。为了兼顾秸秆资源利用、土壤质量改善和作物增产稳产,稻田冬闲期稻秸全量覆盖与种植绿肥协同还田利用模式是一种较好的选择。     

Long-Term Effect of Nitrogen and Tillage Management on Soil Carbon Pools in the Semiarid Northern Great Plains

No-tillage and manure application effect on soil organic carbon (SOC) and total nitrogen (N) concentrations were studied under a 27-year-old 4-year rotation consisting corn (Zea mays L.)-soybean (Glycine max L.)-wheat (Triticum aestivum L.)-field pea (Pisum sativum L.). Under each crop, four applied N treatments were control, annual urea-N applications at the rate of 45 and 89 kg N ha^?1, and composted beef cattle feedlot manure-N at the rate 179 kg N ha^?1 applied once every four year. For each fertilizer treatment, no-till (NT) and conventional till (CT) were compared for basic soil properties, SOC, and total N within 0–15 cm soil. Manure application significantly reduced soil bulk density and increased SOC and total N over urea-N. Particulate organic matter, mineralizable N, and permanganate-oxidizable C fractions significantly related with SOC. Long-term manure additions and no-tillage had potential to improve soil compaction and maintain SOC over chemical fertilizer N and CT.     

Organic Amendments Influence on Soil Biological Indices and Yield in Rice-Based Cropping System in Coastal Sundarbans of India

The present investigation was carried out in coastal Sundarbans of India to study the effects of farm yard manure, green leaf manure, and vermicompost on biological attributes of soils and yield in rice–tomato, rice–sunflower, and rice–chili cropping system over conventional farmer’s practices (control) by a strip-plot technique for the two consecutive years. The partial substitution of inorganic fertilizers through organics significantly increased the yield of various cropping systems. The use of organic materials significantly improved microbial biomass carbon, fluorescein diacetate hydrolyzing activities, dehydrogenase, and β-glucosidase activity over control, which varied in the tune of 51.6%, 67.4%, 50%, and 62.7%, respectively, due to variation in electrical conductivity (EC) of these soils. The improved soil microbial biomass and enzyme activities act as key driving factor for organic matter decomposition and nutrient transformation in organically amended soils which lead to better yield under such cropping sequences.     

施肥对土壤有机碳含量及碳库管理指数的影响

在华北夏玉米生产体系中,采用田间试验,研究了不同施肥措施下（不施肥、单施有机肥、推荐施肥、习惯施肥和单施化肥）,土壤有机碳含量、活性有机碳含量和碳库管理指数的变化。结果表明:与不施肥相比,单施有机肥土壤有机碳和活性有机碳含量分别增加 11.68%,21.71%。推荐施肥和习惯施肥土壤有机碳含量分别增加 6.57%,7.58%,活性有机碳含量分别增加 8.53%,4.26%。单施化肥土壤有机碳与活性有机碳含量均没有显著增加;施有机肥和推荐施肥土壤碳库管理指数比不施肥分别高 31.79,13.01。单施化肥土壤碳库管理指数没有显著变化;土壤活性有机碳与总有机碳、碳库管理指数、玉米子粒产量均存在极显著相关关系。碳库管理指数与玉米子粒产量极显著相关,能够指示土壤生产力的变化。可见在当地土壤肥力条件下,施有机肥或有机无机适当配施能提高土壤有机碳含量和土壤碳库管理指数,有利于改善土壤质量,提高土壤肥力。     

Effect of mineral and organic fertilization on crop yield,nitrogen uptake,carbon and nitrogen balances,as well as soil organic carbon content and dynamics: results from 20 European long-term field experiments of the twenty-first century

Assembled results from 20 European long-term experiments (LTE), mainly from the first decade of the twenty-first century, are presented. The included LTEs from 17 sites are the responsibility of institutional members of the International Working Group of Long-term Experiments in the IUSS. Between the sites, average annual temperatures differ between 8.1 and 15.3°C, annual precipitation between 450 and 1400 mm, and soil clay contents between 3 and 31%. On average of 350 yield comparisons, combined mineral and organic fertilization resulted in a 6% yield benefit compared with mineral fertilization alone; in the case of winter wheat, the smallest effect was 3%, the largest effect, seen with potatoes, was 9%. All unfertilized treatments are depleted in soil organic carbon (SOC), varying between 0.36 and 2.06% SOC. The differences in SOC in unfertilized plots compared with the respective plots with combined mineral (NPK) and organic (10 t ha^?1 farmyard manure) fertilization range between 0.11 and 0.72%, with an average of 0.3% (corresponding to ～15 t ha^?1). Consequently, the use of arable soils for carbon sequestration is limited and of low relevance and merely depleted soils can temporarily accumulate carbon up to their optimum C content.     

长期施用有机肥对瘠薄红壤有效碳库及碳库管理指数的影响

主要分析了长期施用有机肥对瘠薄红壤有效碳库(微生物量碳,易氧化碳,矿化碳)及碳库管理指数(CPMI)的影响.结果表明:长期施用有机肥对土壤有效碳库和碳素有效率有很大影响,绿肥,稻草秸秆肥和厩肥处理的土壤有机碳,微生物量碳、易氧化碳、矿化碳的数量、碳素有效率明显高于对照处理的土壤。施肥对全碳、矿化碳的影响为:厩肥>绿肥>秸秆稻草肥>本田还田>对照,对微生物量碳的影响为:绿肥>厩肥>稻草秸秆肥>本田还田>对照,对活性碳(CA)、CPMI,碳素有效率A、B、C的影响为:绿肥>稻草秸秆肥>厩肥>本田还田>对照。在提高CA、CPMI方面,绿肥和稻草秸秆肥优于厩肥。相关分析表明:土壤有效碳库和碳素有效率与土壤化学性质相关或极相关,CPMI与土壤养分因子相关或极相关,反映了农业生产措施对土壤碳库的影响,可以运用CPMI来评估土壤碳库的变化。     

Critical carbon inputs to maintain soil organic carbon stocks under long‐term finger‐millet (Eleusine coracana [L.] Gaertn.) cropping on Alfisols in semiarid tropical India

Enrichment of soil organic carbon (SOC) stocks through sequestration of atmospheric CO₂ in agricultural soils is important because of its impacts on adaptation to and mitigation of climate change while also improving crop productivity and sustainability. In a long‐term fertility experiment carried out over 27 y under semiarid climatic condition, we evaluated the impact of crop‐residue C inputs through rainfed fingermillet (Eleusine coracana [L.] Gaertn.) cropping, fertilization, and manuring on crop yield sustainability and SOC sequestration in a Alfisol soil profile up to a depth of 1 m and also derived the critical value of C inputs for maintenance of SOC. Five treatments, viz., control, farmyard manure (FYM) 10 Mg ha^–1, recommended dose of NPK (50 : 50 : 25 kg N, P₂O₅, K₂O ha^–1), FYM 10 Mg ha^–1 + 50% recommended dose of NPK, and FYM 10 Mg ha^–1 + 100% recommended dose of NPK imposed in a randomized block design replicated four times. Application of FYM alone or together with mineral fertilizer resulted in a higher C input and consequently built up a higher C stock. After 27 y, higher profile SOC stock (85.7 Mg ha^–1), C build up (35.0%), and C sequestration (15.4 Mg C ha^–1) was observed with the application of 10 Mg FYM ha^–1 along with recommended dose of mineral fertilizer and these were positively correlated with cumulative C input and well reflected in sustainable yield index (SYI). For sustenance of SOC level (zero change due to cropping) a minimum quantity of 1.13 Mg C is required to be added per hectare per annum as inputs. While the control lost C, the application of mineral fertilizer served to maintain the priori C stock. Thus, the application of FYM increased the C stock, an effect which was even enhanced by additional amendment of mineral fertilizer. We conclude that organic amendments contribute to C sequestration counteracting climate change and at the same time improve soil fertility in the semiarid regions of India resulting in higher and more stable yields.     

苏打盐碱水灌溉的土壤添加石膏肥和有机肥后水溶性碳和微生物碳研究

Microbial biomass carbon (MBC), a small fraction of soil organic matter, has a rapid turnover rate and is a reservoir of labile nutrients. The water-extractable carbon pools provide a fairly good estimate of labile C present in soil and can be easily quantified. Changes in soil MBC and water-extractable organic carbon pools were studied in a 14-year long-term experiment in plots of rice-wheat rotation irrigated with canal water (CW), sodic water (SW, 10-12.5 mmol c L-1 residual sodium carbonate), and SW amended with gypsum with or without application of organic amendments including farmyard manure (FYM), green manure (GM), and wheat straw (WS). Irrigation with SW increased soil exchangeable sodium percentage by more than 13 times compared to irrigation with CW. Sodic water irrigation significantly decreased hot water-extractable organic carbon (HWOC) from 330 to 286 mg kg-1 soil and cold water-extractable organic carbon (CWOC) from 53 to 22 mg kg-1 soil in the top 0-7.5 cm soil layer. In the lower soil layer (7.5-15 cm), reduction in HWOC was not significant. Application of gypsum alone resulted in a decrease in HWOC in the SW plots, whereas an increase was recorded in the SW plots with application of both gypsum and organic amendments in both the soil layers. Nevertheless, application of gypsum and organic amendments increased the mean CWOC as compared with application of gypsum alone. CWOC was significantly correlated with MBC but did not truly reflect the changes in MBC in the treatments with gypsum and organic amendments applied. For the treatments without organic amendments, HWOC was negatively correlated with MBC (r = 0.57*) in the 0-7.5 cm soil layer, whereas for the treatments with organic amendments, both were positively correlated. Irrigation with SW significantly reduced the rice yield by 3 t ha-1 and the yield of rice and wheat by 5 t ha-1 as compared to irrigation with canal water. Application of amendments significantly increased rice and wheat yields. Both the rice yield and the yield of rice and wheat were significantly correlated with MBC (r = 0.49**-0.56**, n = 60). HWOC did not exhibit any relation with the crop yields under the treatments without organic amendments; however, CWOC showed a positive but weak correlation with the crop yields. Therefore, we found that under sodic water irrigation, HWOC or CWOC in the soils was not related to MBC.     

Effect of different fertilization modes on soil organic carbon sequestration in acid soils

ABSTRACT

A meta-analysis of 297 treatment data from the Vezaiciai Branch of the Lithuanian Research Centre for Agriculture and Forestry long-term field experiment published from 2006 to 2015 was used to characterize the changes in SOC under different fertilization treatments and residue management practices in Lithuania’s acid soil. A meta-analysis was performed to quantify the relative annual change (RAC) of SOC content and the average RAC rate of SOC under four fertilization modes (farmyard manure (FYM) (40?t?ha^?1)); alternative organic fertilizers (in the manure background (40?t?ha^?1)); FYM (60?t?ha^?1); alternative organic fertilizers (in the manure background (60?t?ha^?1)) in two soil backgrounds (naturally acid and limed soil). The average RAC under four fertilization modes was 1.46 g?kg^?1?yr^?1, indicating that long-term fertilization had considerable SOC sequestration potential. Incorporation of alternative organic fertilizers in unlimed soil showed negative effects (?0.39 and ?0.66 g?kg^?1?yr^?1) in the observed long-term experiment. The RAC in the limed soil with incorporated organic fertilizers (FYM and alternative organic fertilizers), compared to the control, and varied from 0.25 g?kg^?1?yr^?1 in the treatment with incorporated alternative organic fertilizers (in the manure background (40?t?ha^?1)) to 0.71 g?kg^?1?yr^?1 in the soil with FYM (60?t?ha^?1). In this study, the average RAC rate of SOC under organic fertilization treatments in limed soil (5.07–6.54%) was longer than organic fertilization in unlimed soil (2.11–3.49%), which might be attributed to the application of organic manure that would result in a slow release of fertilizer efficiency. Our results indicate that the application of manure (40 or 60?t?ha^?1) showed the greatest potential for C sequestration in agricultural soil and produced the longest SOC sequestration duration.     

Crop rotation with plastic mulching increased soil organic carbon and water sustainability: A field trial on the Loess Plateau

Appropriate crop rotations are beneficial for food security and carbon sequestration. In cool and semiarid rain-fed areas, however, the effect on carbon sequestration in soil and the soil–crop system is not clear. In this study, a crop rotation field experiment was carried out on the Loess Plateau, China, involving (1) wheat continuous cropping (WCC), (2) maize continuous cropping (MCC), (3) potato continuous cropping (PCC) and (4) wheat–maize–potato rotating cropping (RC). All treatments were tilled once, and then, plastic mulched immediately to inhibit evaporation. We found that the rotating cropping system improved water storage in the 0–300 cm soil profile by 65.8 mm through the 6 years, while MCC depleted deep soil moisture. In a drought year, total dry matter (DM) for the rotating cropping was greater by 23.9% and 79.3% and harvested carbon quantity (HCQ) by 0.6 and 1.8 Mg ha⁻¹ compared with WCC and MCC systems, respectively. Total evapotranspiration significantly decreased by 14.5% compared with MCC, with no significant change compared with WCC and PCC. The soil organic carbon (SOC) concentration at 20–30 cm depth in the rotating cropping system was 36.0%, 28.0% and 30.3% greater than those of WCC, MCC and PCC, respectively. Similarly, the SOC sequestration rate at this depth was higher by 3.8, 3.2 and 3.4 Mg ha⁻¹, respectively. The pure carbon accumulation (PCA) of the rotating cropping system significantly increased compared with WCC and PCC, resulting in increased water use efficiency of pure carbon accumulation (WCP) by 11.1, 2.2 and 3.1 Mg ha⁻¹ mm⁻¹ compared with the WCC, MCC and PCC systems, respectively. Overall, the rotating cropping (RC) system maintained better soil water conditions, sustained crop development and SOC sequestration, especially optimizing the relationship between crop water utilization and SOC sequestration in soil–crop system in the cool semiarid rain-fed area.     

Soil carbon pools of reclaimed minesoils under grass and forest landuses

Minesoils are characterized by low soil organic matter and poor soil physicochemical environment. Mine soil reclamation process has potential to restore soil fertility and sequester carbon (C) over time. Soil organic C (SOC) pool and associated soil properties were determined for reclaimed minesoils under grass and forest landuses of varied establishment year. Three grassland sites of 30, 9, and 1 years after reclamation (G30, G9, and G1) and two forest sites, 11 years after reclamation (RF) and undisturbed stand of 40 years (UF), were selected within four counties (Morgan, Muskingum, Noble, and Coshocton) of southeastern Ohio. Soil bulk density (BD) of reclaimed forest (RF) soil was significantly higher than undisturbed forest (UF) soils within 10–40 cm soil depth profile. Reclamation process increased soil pH from slightly acidic to alkaline and decreased the soil EC in both landuses. Among grassland soils, significant changes in SOC and total soil N contents were observed within 0–10 cm soil depth. SOC contents of G30 (29.7 Mg ha⁻¹) and G9 (29.5 Mg ha⁻¹) were significantly higher than G1 soils (9.11 Mg ha⁻¹). Soil N content was increased from G1 (0.95 Mg ha⁻¹) to G9 (2.00 Mg ha⁻¹) site and then the highest value was found under G30 (3.25 Mg ha⁻¹) site within 0–10 cm soil depth. UF soils had significantly higher SOC and total N content than RF soils at 0–10 and 10–20 cm soil depths. Copyright © 2009 John Wiley & Sons, Ltd.