Microorganisms and organic carbon (C) pool composition are vital in regulating soil organic matter mineralization. However, our understanding of how parent materials and fertilizers affect this process is still limited. In this two-year study, the changes of cumulative soil organic C and nitrogen (N) mineralization and C and N pools (total, labile, and recalcitrant), C- and N-cycling enzymes, bacterial composition, and C- and N-cycling gene and their interactions were analyzed for soils developed on loess and river alluvium. These soils were under rice-rape seed rotation, and no fertilization (Control), NPK (NPK), and NPK plus organic manure (NPKM) were applied; treatments were arranged into a completely randomized design. Soil organic C mineralization was influenced by soil parent material and fertilization, whereas no interactive effects were found for soil N mineralization. The river alluvium promoted 2.24 times higher C and 1.27 times higher N mineralization than loess; fertilization intensified C and N mineralization in 1.70 and 1.22 times only in loess. Soil C and N fractions were influenced by the parent material, with 1.39 and 1.10 times higher effects found in soils formed on river alluvium. NPKM increased the content of total organic C in 1.31 times, labile C in 1.24 times, recalcitrant C in 1.34 times, total N in 1.21 times, and recalcitrant N in 1.17 times in loess soil. Similarly, in river alluvium soil, the increases were 1.41、1.21、1.53、1.23 and 1.28 times. Fertilization with NPKM increased C- and N-cycling enzyme activities in both soils. Parent material and fertilization shifted bacterial composition by changing pH, subsequently influencing N-cycling genes. However, only parent material affected C-cycling genes. Thus, C and N fractions play a direct role in the mineralization process of soil organic C, while bacteria indirectly influenced the C mineralization processes by promoting the enzyme activities.

In the arid and semi- arid areas in China, the emergence rate of crops is usually reduced by the undecomposed residues, as the areas are characterized in low temperature and insufficient soil moisture. Thus, an innovative method of straw returning is needed to solve the above problems. In this study, high- density organic matter (HDOM) was made of chopped wheat straw (CWS). The HDOM of wheat straw (HDOM- W) without exogenous addition is one treatment, the HDOM- W containing 10% wheat straw biochar (HDOM- WB) and elemental sulfur (HDOM- WS) in weight categorized as two other treatments. The effects of HDOM on soil and crop growth were systematically evaluated through field in situ and laboratory incubation experiments. The results showed that compared to CWS, wheat germination rate was not significantly decreased in the HDOM- W treatment; the biomass, total N and P concentrations of wheat in HDOM- WS were increased by 137.9%, 137.1%, and 141.8%, respectively (P < 0.05); wheat K concentration in HDOM- WB was significantly increased by 39.7% (P < 0.05). Therefore, application of HDOM in soils can improve seed bed, promote crop growth and increase nutrient content, which eventually elevating soil fertility. Organic materials like crop straws, tree branches, grasses off the farmland, abandoned wood furniture, etc. can be all returned to the field as HDOM to elevate soil fertility. The application of HDOM can be used as an innovative environmental protection technology to tackle the problem of organic waste disposal and sustainably maintain soil quality.

[目的]研究不同有机物料的有机磷组成及其作为磷源施用后的供磷能力,为化肥磷的有机替代奠定理论基础.[方法]供试有机物料包括粪肥类(猪粪、羊粪)、绿肥类(豌豆、苜蓿和绿豆)、秸秆类(小麦秸秆、玉米秸秆和油菜秸秆).分析了8种有机物料的全磷、有机磷含量和C/P值,采用Bowman-Cole方法测定了有机磷中的活性(LOP)、中活性(MLOP)、中稳性(MROP)和高稳性有机磷(HROP)4个组分的含量.用供试的8种有机物料进行了小麦盆栽试验,分析了土壤速效磷含量、小麦吸磷量与不同有机物料的有机磷组成、碳/磷(C/P)值之间的关系.[结果]粪肥、绿肥和秸秆中的全磷含量分别为5.49～5.52、1.19～2.59、0.57～1.07 g/kg,有机物料中有机磷含量占全磷的比例在31.3％～55.2％,除绿豆秸秆外,有机磷含量小于无机磷.有机磷中LOP、MLOP、MROP和HROP的平均比例分别为8.5％、45.2％、41.5％和4.9％.LOP平均含量以粪肥类(175.5 mg/kg)>绿肥类(67.03 mg/kg)>秸秆类(25.8 mg/kg);以猪粪、绿豆秸秆的MLOP含量相对较高;MROP含量羊粪>猪粪>苜蓿秸秆>绿豆秸秆>豌豆秸秆>玉米秸秆>油菜秸秆>小麦秸秆;HROP在粪肥中的含量显著高于其他类型物料.施用绿肥和粪肥显著增加了小麦的吸磷量和生物学产量,而施用秸秆则不同程度降低了小麦的吸磷量和生物学产量.小麦吸磷量与土壤速效磷含量呈线性正相关关系,与有机物料C/P值呈极显著负相关关系,与LOP、MLOP、MROP呈极显著正相关关系,与HROP相关性不显著;土壤速效磷与有机物料C/P值呈负相关关系.[结论]供试有机物料中的全磷含量以粪肥类>绿肥类>秸秆类,无机磷含量均大于有机磷含量(绿豆秸秆除外),有机磷以中活性和中稳性有机磷为主.绿肥类和粪肥类物料中含磷量高、且C/P值较低,作为肥料使用能显著增加土壤速效磷含量、小麦生物学产量和吸磷量,可以有效替代一定比例的磷肥.而秸秆类有机物料含磷量较低,且C/P值较高,不适宜作为化肥磷的有机替代物料.

我国西北地区气温较低,秸秆直接还田腐解慢、养分循环慢、当季利用率低、影响作物出苗,导致秸秆还田率不高.针对以上问题,本研究以小麦秸秆为原料,以硫磺粉(养分活化剂)和麦秸生物炭(养分吸附剂)为外源添加材料,制成秸秆颗粒.硫磺粉的添加质量比为3％(WS3)、5％(WS5)、10％(WS10),生物质炭的添加质量比为5％(WC5)、10％(WC10)、15％(WC15),以秸秆颗粒(WK)、剪碎秸秆(W,W6)及无秸秆(CK)为对照,通过盆栽试验探究了秸秆颗粒对土壤速效养分及小麦生长的影响.结果表明:秸秆颗粒较剪碎秸秆处理相比,能显著提高土壤速效养分及小麦生物量和植株全量氮、磷、钾含量,添加硫磺或生物炭的秸秆颗粒提升效果更明显.各处理土壤硝态氮含量以WS3处理最高,较W处理提高14.44％;铵态氮含量以WC5处理最高,较W处理提高40.93％;速效磷含量以WS10处理最高,较W处理提高23.42％;速效钾含量以WC5处理最高,较W处理提高9.05％;差异均达显著水平(P<0.05).小麦生物量以WS5处理最高,较WK处理提高29.61％;全氮含量以WS10最高,较WK处理提高11.44％;全磷含量以WS10处理最高,较WK处理提高21.82％;全钾含量以WC15最高,较WK处理提高12.53％;差异均达显著水平(P<0.05).综上可知,秸秆颗粒在西北地区实现秸秆还田和养分循环,维持土壤肥力等方面具有很大应用前景.

由于科学施肥指导工作和生产实际的脱节,过量施用磷肥的现象普遍存在,进而造成大量磷素在土壤中累积.准确评价土壤中磷素的有效性是土壤磷素科学管理的基础.国际上梯度扩散薄膜技术(DGT)和传统方法相比可以更为准确地反映土壤中元素的生物有效性.以黄土高原具有代表性的60个土壤样品为研究对象,采用传统Olsen法和DGT技术评价多年磷肥投入不均条件下黄土高原地区土壤磷储量及其有效性现状,研究了DGT技术测定的DGT-P与全磷、Olsen-P之间的关系,并利用通径分析探究了土壤磷素有效性和土壤相关理化指标之间的关系.结果表明:黄土高原地区土壤磷素分布不均匀,缺磷与富磷现象并存,富磷土壤主要是耕地样品.磷素活化系数(Olsen-PAC)小于2.0％的土壤样品占76.67％,绝大部分土壤样品磷素有效性低.耕地磷肥投入量过高,活化土壤中的无效磷是黄土高原地区磷素科学管理的主要目标.土壤DGT-P与全磷、Olsen-P呈显著相关性(P<0.01).黏粒对土壤磷素有效性的直接影响最大,对Olsen-PAC的影响为正效应,对DGT法测定的磷素活化系数(DGT-PAC)的影响为负效应.土壤黏粒含量越高,有效磷库越大,土壤中供植物吸收利用的磷反而越少.

Under different nitrogen levels,to reveal the accumulation and transportation regular of spring barley ni-trogen content in Tongliao district and making an analysis about the accumulation and transportation of two barley va-rieties organ nitrogen content on Inner Mongolia university for nationalities experimental base. The results indicating that with the increase of nitrogen levels, the leaf, stem and grain nitrogen content increased. Under the 270kg·hm-2 ni-trogen level, Mengpi 1 and Ganpi 4 maximum values of leaves respectively 53.25%and 36.31%higher than the con-trast and stems were 38.16%and 54.29% higher than the contrast, the grains were 21.88%and 21.22%higher than the contrast. With the increase of nitrogen levels, before flowering and after flowering the nitrogen accumulation of the two barley varieties are all increasing. Under the 270kg·hm-2 nitrogen level, Mengpi 1 and Ganpi 4 before flowering nitrogen accumulation respectively 297.42% and 198.65% higher than the contrast,after flowering 222.55% and 174.46% higher than the contrast.