Crop Yield and Soil Properties in the First 3 Years After Biochar Application to a Calcareous Soil

It remains unclear whether biochar applications to calcareous soils can improve soil fertility and crop yield. A long-term field experiment was established in 2009 so as to determine the effect of biochar on crop yield and soil properties in a calcareous soil. Five treatments were： 1） straw incorporation; 2） straw incorporation with inorganic fertilizer; 3）, 4） and 5） straw incorporation with inorganic fertilizer, and biochar at 30, 60, and 90 t ha-l, respectively. The annual yield of either winter wheat or summer maize was not increased significantly following biochar application, whereas the cumulative yield over the first 4 growing seasons was significantly increased. Soil pH, measured in situ, was increased by a maximum of 0.35 units after 2 yr following biochar application. After 3 yr, soil bulk density significantly decreased while soil water holding capacity increased with adding biochar of 90 t ha^-1. Alkaline hydrolysable N decreased but exchangeable K increased due to biochar addition. Olsen-P did not change compared to the treatment without biochar. The results suggested that biochar could be used in calcareous soils without yield loss or significant impacts on nutrient availability.     

Effects of Agricultural Practices on Soil Organic Nitrogen Fractions in an Inceptisol of a Cocoa Plantation

The effect of agricultural practices on soil organic nitrogen （N） fractions in a cocoa plantation has not been much revealed till now. Despite the fact that soil organic N has been long admitted for its importance to maintain soil fertility. Presented field experiment was conducted in Kaliwining Experimental Station, Indonesian Coffee and Cocoa Research Institute （ICCRI）, Jember, East Java, Indonesia, to investigate the effect of cocoa farm management, namely fertilization, weeding and soil tillage on the content of soil organic N fractions. The design of experiment was arranged in a split-split plot with two levels of weeding as main plots, two levels of soil tillage as subplot and three different fertilizer treatments as sub-sub plot. The analysis of soil N including total N and soil organic N fractions, namely, total hydrolized N, ammonium N, amino sugar N and amino acid N, were performed. The result showed that the effect of fertilization treatment was significant to the content of total N, ammonium N, amino sugar N and amino acid N. No-tillage treatment resulted in total N and amino sugar-N content increasing by 8% and 24%, respectively, over tillage treatment. Slashing treatment caused increase of the total N by 3% from herbicide treatment, whilst decrease of ammonium N and amino sugar N by 7% and 24%, respectively.     

秸秆和生物质炭对苹果园土壤容重、阳离子 交换量和氮素利用的影响

【目的】中国苹果园土壤有机碳含量较低,氮肥施用量偏高。本研究为苹果生产上合理应用秸秆和生物质炭来提高土壤缓冲性能和氮肥利用效率提供依据。【方法】以两年生富士/平邑甜茶为试材,采用15N标记示踪技术,研究添加秸秆和生物质炭对土壤容重、阳离子交换量、植株生长及氮素转化（树体吸收、氨挥发、N2O排放和土壤残留）的影响。试验共设4个处理：对照（CK）、单施氮肥（N）、施用氮肥并添加生物质炭（N+B）和施用氮肥并添加秸秆(N+S)。【结果】不同处理的土壤容重在0-5 cm和5-10 cm两个土层中的变化趋势一致。CK与N处理间差异不显著,但均显著高于N+B和N+S处理;两个添加外源碳的处理间,N+B处理的土壤容重显著低于N+S处理。与N处理相比,N+S和N+B处理的0-5 cm和5-10 cm两个土层的容重分别降低了0.06、0.09 g•cm-3和0.07、0.11 g•cm-3。与CK（18.32 cmol•kg-1）和N（19.61 cmol•kg-1）处理相比,N+S（22.27 cmol•kg-1）和N+B处理（25.35 cmol•kg-1）显著提高了0-10 cm土层土壤阳离子交换量,并且以N+B处理效果较好。3个施氮处理间植株总干重、15N积累量和15N利用率均以N+B处理最高,N+S处理次之,N处理最低。与CK相比,3个施氮处理（N、N+S和N+B处理）的氨挥发量均显著增加。与N处理相比,添加外源碳的两个处理（N+S和N+B处理）显著减少了氨挥发损失量,以N+B处理减少幅度最大。与CK相比,3个施N处理（N、N+S和N+B处理）的N2O排放量均显著增加,以N+B处理最高,其次为N+S处理,N处理最低,可见添加外源碳的两个处理的N2O排放量均有所增加,但3个施氮处理间差异不显著。去掉CK本底值后,N、N+S和N+B处理的氮素总气态损失量（氨挥发+N2O排放）占施氮量的比例分别为6.54%、4.33%和3.04%。可见,添加秸秆和生物质炭显著降低了氮素气态损失,以N+B处理效果较好。耕层土壤（0-50 cm）的15N残留量以N+B处理最高,N+S处理次之,N处理最低;而深层土壤（50-100 cm）则以N处理最高,N+S处理次之,N+B处理最低。3个施氮处理间,N回收率（树体吸收+土壤残留）以N+B处理最高,为42.26%,其次为N+S处理（37.22%）,N处理最低（31.54%）;N损失率以N处理最高,为68.46%。其次为N+S处理（62.78%）,N+B处理最低（57.74%）。【结论】添加秸秆和生物质炭显著降低了土壤容重,提高了土壤阳离子交换量,促进了苹果植株生长和对肥料氮的吸收,增加了土壤对氮的固定,减少了氮肥的气态损失,提高了氮肥利用率,其中以添加生物质炭的效果较好。     

Estimation of the Biological Methods of Assessing Soil N-Supplying Capacity in Calcareous Soil

Although many biological methods are used to determine soil nitrogen supplying capacity, there are certain differences in the results for different types of soils and various ways of measurement due to the complexity of soil N conformation, the high variance of soil and microorganism, and the difference of environment. Therefore, it is not clear about which biologic incubation method is better for calcareous soil. In this study, pot experiments were performed by using 25 different calcareous surface soil samples on the Loess Plateau and taking the N uptake of wheat and corn with leaching soil initial nitrate and without leaching in pot experiments as the control to investigate the difference of eight biological incubation methods for reflecting soil nitrogen supply capacity. The eight biological methods are waterlogged incubation, aerobic incubation for 2 weeks and for 4 weeks, dry-wet alternation aerobic incubation for 2 weeks, long-term alternate leaching aerobic incubation (and N mineralization potential, N^o), short-term leaching aerobic incubation, microbial biomass carbon (B_c), and microbial biomass nitrogen (B_N) method, respectively. Among these methods, the dry-wet alternation aerobic incubation and aerobic incubation for 4 weeks were the modification of the method of aerobic incubation for 2 weeks according to the actual farmland moisture. The results showed that the correlation coefficients between these methods and crop uptake N w with leaching soil initial nitrate were 0.530, 0.700, 0.777, 0.768, 0.764 (and 0.790, N₀), 0.650, 0.555, and 0.465, respectively (r_0.05 = 0.369, r_0.01 = 0.505). While without leaching soil initial nitrate, their coefficients were 0.351, 0.963, 0.962, 0.959, 0.825 (and 0.812, N₀), 0.963, 0.289, and 0.095, respectively (r_0.05 = 0.369, r_0.01=0.505). In conclusion, excluding the soil initial nitrate, the correlation coefficients between the eight methods and crop uptake N were, from high to low, N₀, aerobic incubation for 4 weeks, dry-wet alternation aerobic incubation for 2 weeks, and long-term alternate leaching aerobic incubation, while including the soil initial nitrate the correlation coefficients between them increased significantly and the values were all beyond 0.950 for these four methods, including aerobic incubation for 2 weeks and for 4 weeks, dry-wet alternation aerobic incubation for 2 weeks and short-term leaching aerobic incubation. The waterlogged incubation method, B_C and B_N in the calcareous soil, had lower correlation coefficient with crop uptake nitrogen compared with other methods. Thus, dry-wet alternation aerobic incubation for 2 weeks was a better index for evaluating calcareous soil N supply capacity due to some other methods having disadvantages and not suitable for the actual farmland characteristics.     

硝化/脲酶抑制剂对石灰性潮土N2O减排效果及氮素转化的比较

以华北平原石灰性潮土为对象,采用室内静态培养方法,在土壤中添加不同类型的抑制剂(硝化抑制剂、脲酶抑制剂),监测N_2O和无机氮随时间变化的特征,对比分析何种添加剂减排N_2O效果明显,为其在农业生产中的应用提供科学依据。试验设置7个处理:不施肥(CK);只施尿素(U);尿素和2-氯-6-三氯甲基吡啶(Nitrapyrin,由中化集团公司代理)同时施用(U+NP);尿素和推荐用量2-氯-6-三氯甲基吡啶(Nitrapyrin,由陶氏化学公司代理)同时施用(U+NPD);尿素和2倍推荐用量2-氯-6-三氯甲基吡啶(Nitrapyrin,由陶氏化学公司代理)同时施用(U+2NPD);尿素和双氰胺同时施用(U+DCD);尿素和N-丁基硫代磷酰三胺同时施用(U+n BPT),共培养56 d。在培养第1、2、3、5、7、10、14、19 d采气测定N_2O和CO_2,气体监测到培养第19 d为止;在培养的第0、1、3、7、14、21、28、42、56 d进行破坏性取样,监测土壤氮素转化。结果表明:供试硝化抑制剂能够降低87.4%~99.6%的N_2O排放,脲酶抑制剂降低30.0%N_2O排放;氮素转化过程中,硝化抑制剂处理只有0.03%~0.84%的铵态氮转化为N_2O,脲酶抑制剂处理有4.69%的铵态氮转化为N_2O。DCD和陶氏公司Nitrapyrin产品在抑制N_2O排放的效果上无显著差异,与推荐用量陶氏公司Nitrapyrin相比,施用2倍推荐量并没有显著降低N_2O排放。综上,供试硝化抑制剂能够显著降低石灰性土壤N_2O的排放,减排效果最好的处理为U+NP,陶氏公司Nitrapyrin产品按推荐用量施用即可。     

Long Term Effects of Farming System on Soil Water Content and Dry Soil Layer in Deep Loess Proifle of Loess Tableland in China

Soil water is strongly affected by land use/cover in the Loess Plateau in China. Water stored in thick loessal soils is one of the most important resources regulating vegetation growth. However, soil water in the deep loess proifle, which is critical for maintaining the function of the“soil water pool”is rarely studied because deep proifle soil samples are dififcult to collect. In this study, four experimental plots were established in 2005 to represent different farming systems on the Changwu Tableland：fallow land, fertilized cropland, unfertilized cropland, and continuous alfalfa. The soil water content in the 15-m-deep loess proifles was monitored continuously from 2007 to 2012 with the neutron probe technique. The results showed that temporal variations in soil water proifles differed among the four farming systems. Under fallow land, the soil water content increased gradually over time, ifrst in the surface layers and later in the deep soil layers. In contrast, the soil water content decreased gradually under continuous alfalfa. The distributions of soil water in deep soil layers under both fertilized and unfertilized cropland were relatively stable over time. Thus farming system signiifcantly affected soil water content. Seven years after the start of the experiment, the soil water contents in the 15-m-deep proifles averaged 23.4%under fallow land, 20.3%under fertilized cropland, 21.6%under unfertilized cropland, and 16.0%under continuous alfalfa. Compared to measurements at the start of the experiment, both fallow land and unfertilized cropland increased soil water storage in the 15-m loess proifles. In contrast, continuous alfalfa reduced soil water storage. Fertilized cropland has no signiifcant effect on soil water storage. These results suggest that deep soil water can be replenished under the fallow and unfertilized farming systems. Dry soil layers （i.e., those which have soil water content less than the stable ifeld water capacity） in the subsoil of the Changwu Tableland region can be classiifed as either temporary dry soil layers or persistent dry soil layers. Temporary dry soil layers, which typically form under annual crops, often disappear during wet years. Persistent dry soil layers generally develop under perennial vegetation. Even after removing the vegetation, persistent dry soil layers remain for several decades. This study provides information useful for the conservation and utilization of soil water resources in the Loess Tableland.     

Soil Monitoring System as a Basic Tool for Protection of Soils and Sustainable Land Use in Slovakia

The purpose of soil monitoring system in Slovakia is better to protect the soils with regard to sustainable land use. The main objective is the observation of soil properties concerning the main threats to soil： soil contamination, salinisation and sodification, decline in soil organic matter （SOM）, soil compaction and erosion. Soil monitoring system in Slovakia is consistently running since 1993. Its importance consists of providing the information on changing spatial and temporal variations of soil parameters as well as the evolution of soil quality in topsoil and subsoil. Soil monitoring network in Slovakia is constructed using ecological principles, taking into account all main soil types and subtypes, SOM, climatic regions, emission regions, polluted and non-polluted regions as well as various land use. The results of soil monitoring of 318 sites on agricultural land in Slovakia have been presented. Soil properties are evaluated according to the main threats to soil relating to European Commission recommendation for European soil monitoring performance as follows： soil contamination, soil salinization and sodification, decline in SOM, soil compaction and erosion. The most significant change has been determined in physical properties of soils. The physical degradation was especially manifested in compacted and the eroded soils. About 50% of agricultural land is potentially affected by soil erosion in Slovakia. In addition, decline in SOM and available nutrients indicate the serious facts on evaluation and extension of soil degradation processes during the last period in Slovakia. Obtained measured data and required outputs are reported to Joint Research Centre （JRC） in lspra （Italy） and European Environmental Agency （EEA） in Copenhagen （Denmark）. Finally, soil monitoring system thus becomes a basic tool for protection of soils and sustainable land use as well as for the creation of legislatives not only in Slovakia, but in EU, too.     

Soil Quality Assessment of Acid Sulfate Paddy Soils with Different Productivities in Guangdong Province,China

Land conversion is considered an effective measure to ensure national food security in China, but little information is available on the quality of low productivity soils, in particular those in acid sulfate soil regions. In our study, acid sulfate paddy soils were divided into soils with high, medium and low levels based on local rice productivity, and 60 soil samples were collected for analysis. Twenty soil variables including physical, chemical and biochemical properties were determined. Those variables that were significantly different between the high, medium and low productivity soils were selected for principal component analysis, and microbial biomass carbon （MBC）, total nitrogen （TN）, available silicon （ASi）, pH and available zinc （AZn） were retained in the minimum data set （MDS）. After scoring the MDS variables, they were integrated to calculate a soil quality index （SQI）, and the high, medium and low productivity paddy soils received mean SQI scores of 0.95, 0.83 and 0.60, respectively. Low productivity paddy soils showed worse soil quality, and a large discrepancy was observed between the low and high productivity paddy soils. Lower MBC, TN, ASi, pH and available K （AK） were considered as the primary limiting factors. Additionally, all the soil samples collected were rich in available P and AZn, but deficient in AK and ASi. The results suggest that soil AK and ASi deficiencies were the main limiting factors for all the studied acid sulfate paddy soil regions. The application of K and Si on a national basis and other sustainable management approaches are suggested to improve rice productivity, especially for low productivity paddy soils. Our results indicated that there is a large potential for increasing productivity and producing more cereals in acid sulfate paddy soil regions.     

猪粪化肥配施对稻田土壤氮素含量及氮肥利用效率的影响

化肥有机肥在农田的配施对改良土壤性质、提高养分利用率具有较好的效果,还提升了有机废弃物的循环利用效率。为此,为明确猪粪化肥配施对南方典型双季稻田土壤氮素含量及氮肥利用效率的影响,在双季稻田系统进行田间定位试验。试验共设置了4个处理,即不施氮肥处理(N0)、50%化学氮肥处理(1/2N)、100%化学氮肥处理(N)和猪粪替代50%氮肥处理(1/2N+M)。测定了稻田土壤全氮、有效氮(铵态氮和硝态氮)、微生物生物量氮、水稻氮含量并计算氮吸收量。结果表明:在定位试验开展后第5~6年,猪粪替代50%氮肥处理土壤全氮含量较100%化学氮肥处理显著提高15%;而不施氮肥导致土壤全氮含量显著下降达20%。猪粪化肥配施显著增加晚稻季土壤铵态氮含量。水稻氮肥吸收主要与氮肥用量、土壤全氮含量、铵态氮含量和微生物生物量氮成正相关。2年内猪粪化肥配施较全量氮肥显著提高了晚稻季水稻氮素吸收及氮肥利用率,提升幅度分别为9.2%~18.0%和19.6%~43.0%,且水稻产量略有提升。早稻季猪粪化肥配施较全量氮肥水稻籽粒产量、水稻氮素吸收及氮肥利用率无显著差异或出现显著下降。研究表明,双季稻体系猪粪替代50%氮肥可提高晚稻季稻田土壤氮素有效性,减少化肥施用并提高氮肥利用率。     

氮肥及硝化抑制剂配合施用对石灰性土壤二氧化碳释放的影响

为研究施用氮肥对同时含有有机碳及无机碳石灰性土壤碳释放的影响,在陕西杨凌进行田间试验,比较了不同施氮量(0、160、220 kg·hm~(-2))及其与硝化抑制剂(DCD)配合(N160、N220及N160+DCD、N220+DCD)对土壤pH值、矿质态氮含量和二氧化碳(CO_2)释放量的影响。结果表明:施用氮肥显著降低了耕层土壤pH;配施DCD后土壤pH降低幅度小于未加DCD处理;加入DCD使氮肥的硝化过程推迟了约20 d;未加DCD处理的土壤CO_2释放量随施氮量增加而增加,试验结束时(施肥37 d后)土壤CO_2累积释放量最高达到167.1 g·m~(-2)。与N0处理相比,N160和N220处理的土壤CO_2累积释放量显著增加,增幅分别为20.9%和25.7%;N160+DCD和N220+DCD处理显著降低了土壤CO_2累积释放量,比对应相同施氮量处理分别降低了13.5%和11.0%。上述结果说明施用氮肥会同时影响石灰性土壤有机碳及无机碳的释放,施用氮肥引起的土壤无机碳的释放值得关注。     

Spatiotemporal Changes in Soil Nutrients:A Case Study in Taihu Region of China

The accurate assessment of the spatiotemporal changes in soil nutrients influenced by agricultural production provides the basis for development of management strategies to maintain soil fertility and balance soil nutrients. In this paper, we combined spatial measurements from 2 157 soil samples and geostatistical analysis to assess the spatiotemporal changes in soil organic carbon （SOC）, total nitrogen （TN）, available phosphorus （AP） and available potassium content （AK） from the first soil survey （in the 1980s） to the second soil survey （in the 2000s） in the Taihu region of Jiangsu Province in China. The results showed that average soil nutrients in three soil types all exhibited the increased levels in the 2000s （except for AK in the yellow brown soil）. The standard deviation of soil nutrient contents increased （except for TN in the paddy soil）. Agricultural production in the 20 years led to increases in SOC, TN, AP and AK by 74, 82, 89 and 65%, respectively, of the Taihu areas analyzed. From the 1980s to 2000s all the nugget/sill ratios of soil nutrients indices were between 25 and 75% （except for AK in the yellow brown soil in the 2000s）, indicating moderate spatial dependence. The ratio of AP in the yellow brown soil in the 2000s was 88.74%, showing weak spatial dependence. The spatial correlation range values for SOC, TN, AP and AK in the 2000s all decreased. The main areas showing declines in SOC, TN and AP were in the northwest. For AK, the main region with declining levels was in the east and middle of western areas. Apparently, the increase in soil nutrients in the Taihu region can be mainly attributed to the large increase in fertilizer inputs, change in crop systems and enhanced residues management since the 1980s. Future emphasis should be placed on avoiding excess fertilizer inputs and balancing the effects of the fertilizers in soils.     

模拟酸雨对灰潮土中铅、镉的浸出特性研究

为了研究酸雨作用下灰潮土铅、镉的释放规律。通过对采自田河村(S1)及河口大桥(S2)灰潮土样品进行模拟酸雨淋溶试验,研究了湖北省孝感地区灰潮土中铅、镉的浸出特性。720 ml的模拟酸雨淋洗后,pH值4.5的模拟酸雨使供试灰潮土镉累积浸出比正常降水增加19.5%(S1)和60.9%(S2),使铅的浸出增加87.7%(S1)和12.9%(S2);pH值3.5的模拟酸雨使灰潮土镉累积浸出比正常降水增加45.6%(S1)和80.3%(S2),使铅的浸出增加183.7%(S1)和424.7%(S2);土样S2的总镉和总铅的含量都要比S1土样高,pH值3.5下呈现出镉和铅累积浸出量也较大。镉的浸出随着淋洗液pH值降低淋出量逐渐增加,铅的浸出则在pH值3.5时出现显著增加。镉与铅都随着酸度增加和淋溶量的增加而逐渐浸出。     

Basic Soil Productivity of Spring Maize in Black Soil Under Long-Term Fertilization Based on DSSAT Model

Increasing basic farmland soil productivity has significance in reducing fertilizer application and maintaining high yield of crops. In this study, we defined that the basic soil productivity （BSP） is the production capacity of a farmland soil with its own physical and chemical properties for a specific crop season under local environment and field management. Based on 22-yr （1990-2011） long-term experimental data on black soil （Typic hapludoll） in Gongzhuling, Jilin Province, Northeast China, the decision support system for an agro-technology transfer （DSSAT）-CERES-Maize model was applied to simulate the yield by BSP of spring maize （Zea mays L.） to examine the effects of long-term fertilization on changes of BSP and explore the mechanisms of BSP increasing. Five treatments were examined： （1） no-fertilization control （control）; （2） chemical nitrogen, phosphorus, and potassium （NPK）; （3） NPK plus farmyard manure （NPKM）; （4） 1.5 time of NPKM （1.5NPKM） and （5） NPK plus straw （NPKS）. Results showed that after 22-yr fertilization, the yield by BSP of spring maize significantly increased 78.0, 101.2, and 69.4% under the NPKM, 1.5NPKM and NPKS, respectively, compared to the initial value （in 1992）, but not significant under NPK （26.9% increase） and the control （8.9% decrease）. The contribution percentage of BSP showed a significant rising trend （P〈0.05） under 1.5NPKM. The average contribution percentage of BSP among fertilizations ranged from 74.4 to 84.7%, and ranked as 1.5NPKM〉NPKM〉NPK〉NPKS, indicating that organic manure combined with chemical fertilizers （I.5NPKM and NPKM） could more effectively increase BSP compared with the inorganic fertilizer application alone （NPK） in the black soil. This study showed that soil organic matter （SOM） was the key factor among various fertility factors that could affect BSP in the black soil, and total N, total P and/or available P also played important role in BSP increasing. Compared with the chemical fertilization, a balanced chemical plus manure or straw fertilization （NPKM or NPKS） not only increased the concentrations of soil nutrient, but also improved the soil physical properties, and structure and diversity of soil microbial population, resulting in an iincrease of BSP. We recommend that a balanced chemical plus manure or straw fertilization （NPKM or NPKS） should be the fertilization practices to enhance spring maize yield and improve BSP in the black soil of Northeast China.     

Characterization of Some Typical Soils of the Miombo Woodland Ecosystem of Kitonga Forest Reserve,Iringa, Tanzania： Physico-Chemical Properties and Classification

Despite the fact that miombo woodland soils have significant implications in global climate change processes, few studies have been done to characterize and classify the soils of the miombo woodland ecosystem of Tanzania. The current study was carried out to map and classify soils of Kitonga Forest Reserve, which is a typical miombo woodland ecosystem, in order to generate relevant information for their use and management. A representative study area of 52 km2 was selected and mapped at a scale of 1：50,000 on the basis of relief. Ten representative soil profiles were excavated and described using standard methods. Soil samples were taken from genetic soil horizons and analyzed in the laboratory for physico-chemical characteristics using standard methods. Using field and laboratory analytical data, the soils were classified according to the FAO-World Reference Base （FAO-WRB） for Soil Resources system as Cambisols, Leptosols and Fluvisols. In the USDA-NRCS Soil Taxonomy system the soils were classified as Inceptisols and Entisols. Topographical features played an important role in soil formation. The different soil types differed in physico-chemical properties, hence exhibit differences in their potentials, constraints and need specific management strategies. Texture varied from sandy to different loams; pH from 5.1 to 5.9; organic carbon from 0.9 g/kg to 20 g/kg; and CEC from 3 cmol/（＋）kg to 24 cmol/（＋）kg. Sustainable management of miombo woodlands ecosystem soils requires reduced deforestation and reduced land degradation.     

KCl煮沸法浸取石灰性土壤可矿化氮存在的问题及改进

用KCl煮沸法浸取石灰性土壤中的可矿化氮时,会造成氨态氮的挥发,浸取出的NH_4~+-N反而比不煮沸时为低。为了解决这一问题,进行了不同温度下的保温静置、水浴加热等处理,浸取出来的铵态氮均未显著增加。采取酸化KCl溶液后再进行煮沸,显著地提高了NH_4~+-N的浸出量,且浸出结果与作物吸氮量有密切的相关性。     

Effects of Long-Term Organic Amendments on Soil Organic Carbon in a Paddy Field A Case Study on Red Soil

Soil organic carbon （SOC） is one of the main carbon reservoirs in the terrestrial ecosystem. It is important to study SOC dynamics and effects of organic carbon amendments in paddy fields because of their vest expansion in south China. A study was carried out to evaluate the relationship between the SOC content and organic carbon input under various organic amendments at a long-term fertilization experiment that was established on a red soil under a double rice cropping system in 1981. The treatments included non-fertilization （CK）, nitrogen-phosphorus-potassium fertilization in early rice only （NPK）, green manure （Astragalus sinicus L.） in early rice only （OM1）, high rate of green manure in early rice only （OM2）, combined green manure in early rice and farmyard manure in late rice （OM3）, combined green manure in early rice, farmyard manure in late rice and rice straw mulching in winter （OM4）, combined green manure in early rice and rice straw mulching in winter （OMS）. Our data showed that the SOC content was the highest under OM3 and OM4, followed by OM1, OM2 and OM5, then NPK fertilization, and the lowest under non-fertilization. However, our analyses in SOC stock indicated a significant difference between OM3 （33.9 t ha^-1） and OM4 （31.8 t ha^-1）, but no difference between NPK fertilization （27 t ha^-1） and nonfertilization （28.1 t ha^-1）. There was a significant linear increase in SOC over time for all treatments, and the slop of linear equation was greater in organic manure treatments （0.276-0.344 g kg-1 yr^-1） than in chemical fertilizer （0.216 g kg^-1 yr^-1） and no fertilizer （0.127 g kg^-1 yr^-1）.     

Changes in Organic Carbon Index of Grey Desert Soil in Northwest China After Long-Term Fertilization

Soil organic carbon （SOC）, soil microbial biomass carbon （SMBC） and SMBC quotient （SMBC/SOC, qSMBC） are key indexes of soil biological fertility because of the relationship to soil nutrition supply capacity. Yet it remains unknown how these three indexes change, which limits our understanding about how soil respond to different fertilization practices. Based on a 22-yr （1990-2011） long-term fertilization experiment in northwest China, we investigated the dynamics of SMBC and qSMBC during the growing period of winter wheat, the relationships between the SMBC, qSMBC, soil organic carbon （SOC） concentrations, the carbon input and grain yield of wheat as well. Fertilization treatments were 1） nonfertilization （control）; 2） chemical nitrogen plus phosphate plus potassium （NPK）; 3） NPK plus animal manure （NPKM）; 4） double NPKM （hNPKM） and 5） NPK plus straw （NPKS）. Results showed that the SMBC and qSMBC were significantly different among returning, jointing, flowering and harvest stages of wheat under long-term fertilization. And the largest values were observed in the flowering stage. Values for SMBC and qSMBC ranged from 37.5 to 106.0 mg kg1 and 0.41 to 0.61%, respectively. The mean value rank of SMBC during the whole growing period of wheat was hNPKM〉NPK_M〉NPKS〉CK〉NPK. But there were no statistically significant differences between hNPKM and NPKM, or between CK and NPK. The order for qSMBC was NPKS〉NPKM〉CK〉hNPKM〉NPK. These results indicated that NPKS significantly increased the ratio of SMBC to SOC, i.e., qSMBC, compared with NPK fertilizer or other two NPKM fertilizations. Significant linear relationships were observed between the annual carbon input and SOC （P〈0.01） or SMBC （P〈0.05）, and between the relative grain yield of wheat and the SOC content as well （P〈0.05）. But the qSMBC was not correlated with the annual carbon input. It is thus obvious that the combination of manure, straw with mineral fertilizer may be benefit to increase SOC and improve soil quality than using only mineral fertilizer.     

Responses of Plant Community and Soil Properties to Inter-Annual Precipitation Variability and Grazing Durations in a Desert Steppe in Inner Mongolia

Grazing can dramatically affect arid grassland communities that are very vulnerable to environmental changes due to its relatively short and sparse ground coverage, low biomass, sandy soil and inter-annual precipitation found in the desert steppe. The study investigates the effects of different grazing durations on vegetation and soil properties of a desert steppe community. The experiment was conducted in Xisu Banner in Inner Mongolia with ifve treatments：CG （continuous grazing）, 40UG （40 d ungrazed）, 50UG （50 d ungrazed）, 60UG （60 d ungrazed） and UG （ungrazed）. The biomass of both shrub and annual-biennial plant communities were signiifcantly decreased by CG. Continuous grazing and 40UG signiifcantly reduced the ANPP （aboveground net primary productivity） by the end of the three year study. 60UG treatment increased soil organic carbon （OC）, total nitrogen concentration （TN） and total phosphorus concentration （TP） concentrations and 50UG increased the TN and total phosphorus concentration （TK） concentrations, whereas CG, 40UG and 50UG decreased soil OC, TP and available phosphorus concentration （AP） concentrations. The perennial plant species of the desert steppe were generally tolerant for grazing. The annual-biennial plant species had large variability in ANPP because of the inter-annual precipitation. Our results highlight that inter-annual precipitation variations could strongly modify the community responses to grazing in arid ecosystems.     

Tillage and Poultry Manure Effects on Soil Physical Properties,Nutrient Status,Growth, Dry Matter and Grain Yield of Sorghum

The effects of different tillage systems and poultry manure on soil physical properties, performance and nutrients in sorghum were studied for three years at Owo, southwest Nigeria. There was factorial combinations of herbicide-based zero tillage （ZT）, manual clearing （MC）, disc ploughing （P）, ploughing plus harrowing （P＋H） and ploughing plus double harrowing （P＋2H）, and two rates of poultry manure at 0 and 7.5 Mg ha^-1. Herbicide-based zero tillage and manual clearing reduced soil temperature and conserved more water than mechanized tillage techniques. Poultry manure reduced soil bulk density and temperature and increased soil water and porosity. There was a percentage decrease of leaf N, P, K, Ca and Mg concentrations, plant height, leaf area, stem girth, root dry weight, dry matter and grain yield in ascending order for herbicide-based zero tillage, manual clearing, ploughing, ploughing plus harrowing and ploughing plus double harrowing while percentage increases were recorded in a descending order for all the various combinations of tillage with poultry manure in that order. Poultry manure in combination with tillage increased dry matter and grain yield by 33.1 and 39.5%, respectively in comparison with tillage only. The manure-zero tillage methods increased dry matter and grain yield by 8% and 15%, respectively when compared with manure-mechanized tillage methods. Zero tillage or manual clearing in combination with 7.5 Mg ha^-1 poultry manure was most suitable for sorghum cultivation.     

Reduction of the Pathogenic Propagules of Fusarium profiferatum by Solar and Combined Soil Amendments

The effects of solarisation using clear, UV stabilized, 25μm low density polyethylene mulching combined with soil amendment of chicken manures 12 th^-1, mixed fungicides of Metalaxyl 2 g-Benlate 1.5 g L^-l, Biocontrol agent of Trichoderma harzianum （T.h.） and NPK fertilizer 180 Kg h^-1, on the survived micro and macrocondia of Fusarium proliferatum （Matsushita） Nirenberg were ascertained during summer 2008. Mulched treatments within 45 and 60 days significantly reduced viable propagules to 6 and 3.4 × l03 cfu1 g soil, respectively at 5 cm depth followed by 15 and 30 cm soil depth. Natural heating of dry soil reduced an initial population of 76 × 10^3 to 46.73, 49 and 49.13 × 103 cfu＇lg soil at 5, 15 and 30 cm depth, respectively. Therefore, Fusarium proliferatum reduced by 85.29 and 89.22% within 45 and 60 days compared to 38% in control aired soil. Application of mulching with T. harzianum caused a worthwhile reduction 84.37% in viable propagules, solar with low doses of Metalaxyl-Benlate further reduced Fusarium propagules at all depths 95.5%. Combining chicken manures proved its reduction of fungi cfu at 5 cm depth only, whereas NPK amendments failed in their reduction effects at various depths. However, almost 95% reduction in Fusarium propagules was achieved at various soil depths when combining Met.-Ben., with soil mulching. Combining T.h. was also proved to be significant in reducing fungus inoculum by 88.58, 96.06% at 5 and 15 cm depth. Generally, manures and NPK fertilizers amended soil found equally effective in reducing cfu of Fusarium at 5 and 15 cm depth similar to polyethylene mulching for both solar duration.