植物篱对紫色土区坡耕地水土流失及土壤肥力的影响

植物篱的水土保持效果已得到广泛的认可，并在世界很多地方推广应用，然而，到目前为止，植物篱对坡耕地土壤肥力的影响规律研究却很少。利用长期定位小区试验，研究了植物篱对坡耕地土壤肥力的影响规律，旨在弄清植物篱提高土壤肥力的作用与效果，不断完善植物篱技术。研究发现，坡耕地在建立植物篱后，土壤粘粒在篱前富积，篱下加剧侵蚀，粘粒的富积与侵蚀沿等高线成水平带状分布;土壤有机质、N、P等主要营养元素出现与土壤颗粒相同的分布规律;对K来说，其分布不受植物篱的影响，表现出较为均一分布的特点。从土壤养分的绝对数量来看，P呈高度富积，而有机质和K则是高度耗竭。因此，坡耕地施肥时可以适当减少P的施用量，增加有机物和K的施用量。针对植物篱带对坡耕地肥力影响的特点，即篱前肥力升高，篱下肥力下降，在坡耕地管理上应特别加强篱下土壤带的培肥，以提高坡面整体生产能力。     

长期不同养分投入对土壤养分和水稻生产持续性的影响

以中国科学院桃源农业生态试验站15a长期田间定位试验为研究对象,分析了不同养分投入对稻田土壤养分和水稻产量可持续性的影响.结果表明,化肥与系统内循环的有机物料循环的肥力效力和产量效应基本一致,有机物料循环更有利于土壤有机质和氮素的积累;在不同养分投入下,土壤耕层有机质和全氮均呈上升趋势,年均增长率分别为1.5%～5.8%和2.5%～9.4%;与试验前相比,不同养分投入耕层磷素变动幅度在-18.3%到30%之间,钾素养分有所亏缺,下降幅度在8.1%～22.6%之间;通过可持续性指数的分析得出,土壤N素养分的可持续性对化肥的依赖性较大,而P、K养分的可持续性则对有机肥的依赖性更高.稻田生态系统具有良好的自维持能力,系统内有机物循环有利于提高稻谷产量的稳定性和可持续性.     

玉米秸秆还田培肥土壤的效果

辽北地区玉米根茬还田、秸秆直接还田或间接还田的3年微区培肥试验研究结果表明,无机肥的增产效果特别明显,而施有机物料,更主要的作用是改善土壤的物理、化学性质、培肥地力,与无肥对照相比,有机无机肥料配合施用可使土壤有机质提高3．06％－27．78％,各有机物料对土壤有机质提高的顺序依次为100％秸秆＞50％秸秆＞土粪＞牛粪＞33％秸秆＞根茬。在含C量相等的条件下,秸秆对土壤有机质的保持和提高好于土粪,土粪好于牛粪。同时,与单施化肥比,有机无机肥料配合施用可使土壤易氧化有机质增加10．91％－20．67％,使浸提腐殖酸提高1．43％－14．28％,使结合态腐殖酸的松／紧比值提高0．07－0．19,HA／FA比值提高0．07－0．24,并且能改善土壤的N、P、K营养状况、土壤水分和土壤孔隙状况,这标志着土壤有机质活性的提高和土壤肥力状况的改善。因此,应该大力提倡玉米秸秆秋季直接还田,其最佳施入量应为当年生产量的30％－50％。     

太原市农业土壤全氮和有机质的空间分布特征及其影响因素

利用GPS定位,2005年在山西省太原市主要农业用地采集土样1821个,分析了全氮和有机质的含量.应用传统统计学和地质统计学方法对数据进行了分析.结果表明,按照1980年全国第二次土壤普查养分分级标准,土壤全氮和有机质的平均含量均属中等水平.通过半方差函数分析,土壤全氮和有机质在一定范围内存在空间相关性;它们的空间相关距离分别为122.4 km和75.6 km;全氮的空间变异主要受结构性因素的影响,而土壤有机质的空间变异是由结构性因素和随机性因素共同作用引起的.太原市土壤全氮含量的空间分布呈现由西南向东北逐渐降低的趋势,而有机质的分布规律较为复杂,它们的空间分布主要受土壤类型、海拔高度、土地利用方式和人类生产活动等因素的影响.土壤全氮与有机质的空间分布存在很大的差异,这与娄烦县、古交市当地土壤受煤粉尘污染严重以及所处地形地貌密切相关.研究揭示了在自然和社会条件十分复杂的情况下太原市土壤全氮和有机质的空间变异规律及其影响因素,为实现土壤肥力评价和养分资源精准管理提供了科学依据.     

长白山苔原草本植物入侵与土壤环境的关系

在对长白山高山苔原西坡样带内132个样方进行植被调查和土壤取样分析的基础上,应用冗余分析(RDA)和典型相关分析方法,探讨了草本植物入侵苔原带程度与苔原土理化性质及环境之间的关系。研究表明,长白山苔原带西坡草本入侵程度区域差异明显,可分为5个不同的入侵等级;海拔、坡度、全钾含量、粘粒含量、有机质含量等10种土壤环境因子与草本植物入侵程度明显相关。RDA分析表明土壤环境因子能解释93%的植物物种多度信息,影响草本植物入侵的主要土壤因子是有机质含量,粘粒含量和坡度;第一对典型变量说明有机质含量与牛皮杜鹃多度正相关,与大白花地榆多度负相关,粘粒含量则相反;第二对典型变量说明海拔、速效氮含量与笃斯越桔、长白老鹳草多度呈负相关。长白山苔原带西坡草本植物在空间分布上是离散的,呈斑块状。可见,草本植物入侵,对生境是有所选择的。土壤有机质含量与灌木多度呈正相关,说明在草本入侵过程中,土壤有机质含量会减少;或者有机质含量减少的地方,灌木生长退化,草本由此开始侵入定植。     

基于GIS的农田土壤肥力评价及其与土体构型的关系

以河南省延津县中低产田为例,选取土壤有机质、全氮、全磷、全钾、速效氮、速效磷、速效钾、pH和阳离子交换量（CEC）等指标作为评价因子,利用ArcGIS 9.2软件和模糊数学方法对土壤肥力进行了综合评价,根据评价结果,分析不同土体构型土壤肥力状况差异.结果表明：该区土壤呈偏碱性状态,全氮、全磷、速效氮、CEC、有机质、速效钾含量偏低,速效磷、全钾含量中等,土壤肥力综合指数为0.14～0.63,整体水平偏低.除速效磷和全钾外,其他土壤肥力指标在不同土体构型间均表现出显著差异,土壤肥力与土体构型关系密切,上壤下粘型土壤的肥力等级相对较高,上壤下砂型次之,通体砂型最低.根据各指标在剖面上的分布状况判断,该区土体结构不良,保水保肥能力差,可针对此特征进行土壤改良.     

Anthropogenic N deposition increases soil organic matter accumulation without altering its biochemical composition

Accumulating evidence indicates that future rates of atmospheric N deposition have the potential to increase soil C storage by reducing the decay of plant litter and soil organic matter (SOM). Although the microbial mechanism underlying this response is not well understood, a decline in decay could alter the amount, as well as biochemical composition of SOM. Here, we used size‐density fractionation and solid‐state ¹³C‐NMR spectroscopy to explore the extent to which declines in microbial decay in a long‐term (ca. 20 yrs.) N deposition experiment have altered the biochemical composition of forest floor, bulk mineral soil, as well as free and occluded particulate organic matter. Significant amounts of organic matter have accumulated in occluded particulate organic matter (~20%; oPOM); however, experimental N deposition had not altered the abundance of carboxyl, aryl, alkyl, or O/N‐alkyl C in forest floor, bulk mineral soil, or any soil fraction. These observations suggest that biochemically equivalent organic matter has accumulated in oPOM at a greater rate under experimental N deposition, relative to the ambient treatment. Although we do not understand the process by which experimental N deposition has fostered the occlusion of organic matter by mineral soil particles, our results highlight the importance of interactions among the products of microbial decay and the chemical and physical properties of silt and clay particles that occlude organic matter from microbial attack. Because oPOM can reside in soils for decades to centuries, organic matter accumulating under future rates of anthropogenic N deposition could remain in soil for long periods of time. If temperate forest soils in the Northern Hemisphere respond like those in our experiment, then unabated deposition of anthropogenic N from the atmosphere has the potential to foster greater soil C storage, especially in fine‐texture forest soils.     

不同耕作和覆盖方式对紫色丘陵区坡耕地水土及养分流失的影响

采用随机区组试验,研究了四川紫色丘陵区坡耕地不同耕作和覆盖方式对玉米生育期中水土及养分流失的影响。结果表明:秸秆覆盖对减少水土流失和增加玉米产量的效果均优于地膜覆盖。秸秆覆盖能显著减少地表径流(73.9%—86.2%),但增加了壤中流(15.4%—156.4%);使径流总量降低32.5%—66.6%,并极显著降低土壤侵蚀总量达96.4%—98.1%。地膜覆盖虽能在一定程度上减少壤中流和径流总深,但差异未达到显著水平。土壤N平均损失量达37.4kg/hm2,其中70.1%经由壤中流流失。秸秆覆盖虽然增加了一定的壤中流N损失,但能减少N流失总量达12.8%—65.1%。土壤P素损失量相对较小,仅为9.32kg/hm2,并主要随侵蚀泥沙迁移,占流失总量的92.1%。土壤K损失量达183.3kg/hm2,其流失载体也主要是侵蚀泥沙,占96.5%。因此,两种覆盖方式均能显著控制土壤P和K的损失。无论是秸秆还是地膜覆盖,与顺坡垄作相比,横坡垄作均能减少地表径流、地下径流、土壤侵蚀量及氮、磷、钾素总流失量,同时还能提高玉米产量。从简便、增产和防治面源污染的角度考虑,紫色土区坡耕地最适宜的种植方式为平作+秸秆覆盖。     

新银合欢篱对紫色土坡地土壤有机碳固持的作用

土壤有机碳的固持对保持土壤肥力以及缓解全球温室效应具有重要意义。本研究通过田间定位试验,探讨了新银合欢（Leucaena Leucocephala）篱对10和15的紫色土农耕地（玉米地）和经济林地（油桃地）表层（0-20cm）土壤有机碳积累的影响。结果表明：种植3年的新银合欢篱的10和15农耕地、10经济林地土壤有机碳密度分别比相应的无植物篱的对照地提高41.53%、43.29%、32.15%。经济林处理土壤有机碳含量、有机碳密度、呼吸强度显著大于农耕地处理;10比15农耕地更有利于土壤有机碳、呼吸速率及微生物量碳提高;农耕地比经济林地更利于微生物生物量维持。各处理下坡比上坡更利于土壤有机碳蓄积,且土壤呼吸强度提高,但土壤微生物商基本相同。不同处理下,土壤有机碳与土壤理化性质相关性各不相同：定植新银合欢篱的10和15农耕地、10经济林地土壤有机碳与有机质含量、土壤微生物碳有极显著的相关性,与全钾呈正相关,与pH负相关;定植新银合欢篱的10和15农耕地呼吸强度与有机碳相关关系均达到了极显著性,10经济林地呼吸强度与有机碳显著相关;土壤微生物指标变化与有机碳的变化趋势一致,能反映土壤质量变化。阐明定植新银合欢篱利于土壤有机碳固持,且能增强土壤微生物活性,提高土壤质量。     

Pathways of soil organic matter formation from above and belowground inputs in a Sorghum bicolor bioenergy crop

When aboveground materials are harvested for fuel production, such as with Sorghum bicolor, the sustainability of annual bioenergy feedstocks is influenced by the ability of root inputs to contribute to the formation and persistence of soil organic matter (SOM), and to soil fertility through nutrient recycling. Using ¹³C and ¹⁵N labeling, we traced sorghum root and leaf litter‐derived C and N for 19 months in the field as they were mineralized or formed SOM. Our in situ litter incubation experiment confirms that sorghum roots and leaves significantly differ in their inherent chemical recalcitrance. This resulted in different contributions to C and N storage and recycling. Overall root residues had higher biochemical recalcitrance which led to more C retention in soil (27%) than leaf residues (19%). However, sorghum root residues resulted in higher particulate organic matter (POM) and lower mineral associated organic matter (MAOM), deemed to be the most persistent fraction in soil, than leaf residues. Additionally, the overall higher root‐derived C retention in soil led to higher N retention, reducing the immediate recycling of fertility from root as compared to leaf decomposition. Our study, conducted in a highly aggregated clay‐loam soil, emphasized the important role of aggregates in new SOM formation, particularly the efficient formation of MAOM in microaggregate structures occluded within macroaggregates. Given the known role of roots in promoting aggregation, efficient formation of MAOM within aggregates can be a major mechanism to increase persistent SOM storage belowground when aboveground residues are removed. We conclude that promoting root inputs in S. bicolor bioenergy production systems through plant breeding efforts may be an effective means to counterbalance the aboveground residue removal. However, management strategies need to consider the quantity of inputs involved and may need to support SOM storage and fertility with additional organic matter additions.     

Response of changes in soil nutrients to soil erosion on a purple soil of cultivated sloping land

Severe soil erosion of cultivated sloping land in hilly areas of Sichuan, China, has resulted in deterioration of soil quality, and therefore has an adverse impact on crop production. A hillslope of 110 m in length was selected with a slope steepness of 10.12% where the soils were classified as Regosols. Soil samples for determining ¹³⁷Cs, soil organic matter (SOM), total N, P, K, available N, P, K and particle size fraction were collected at 10 m intervals along a transect of the hillslope. Loss of soil nutrients owing to soil erosion was studied by using ¹³⁷Cs technique, and the relationships between ¹³⁷Cs-derived soil redistribution rates and soil nutrients were established over the cultivated sloping land in hilly areas of Sichuan, China (30o26′N, 104o28′E). The values of SOM, total N, available N, P, K and the soil particle fractions of size < 0.002 mm were smaller at upper and middle slope positions where ¹³⁷Cs inventories were lower (i.e., soil erosion rates were higher) than at downslope positions where ¹³⁷Cs inventories were higher (i.e., soil erosion rates were lower). The lowest ¹³⁷Cs inventories were found at the hilltop, showing that besides erosion owing to water flow, tillage also contributed to soil losses, and intensive tillage was mostly responsible for severe erosion at upper slope positions. There were significant differences in SOM, total N, available N, P, K and the soil particle fractions of size < 0.002 mm between different slope segments, and these properties were significantly correlated with slope length. These soil properties were also significantly correlated with ¹³⁷Cs inventories, indicating that both ¹³⁷Cs and nutrient concentrations varied with topographical changes. The variation in soil properties was strongly influenced by erosion-induced soil redistribution, and therefore ¹³⁷Cs inventories mirroring soil redistribution rates would be considered as an integrated indicator of soil quality.     

稻草覆盖和香根草篱对红壤水稳性团聚体组成及有机碳含量的影响

基于植物篱和秸秆覆盖控制红壤坡耕地水土流失的长期定位试验,研究香根草篱(H)、稻草覆盖(M)、香根草篱+稻草覆盖(HM)水保措施下红壤水稳性团聚体组成及有机碳分布特征。结果表明:与常规等高农作模式(CK)相比,草篱、稻草覆盖、草篱+稻草覆盖模式下土壤总有机碳含量提高0.07—2.42 g/kg。草篱对土壤团聚体组成及其结合有机碳的影响在篱内效果显著,随着与草篱距离增大影响减弱。草篱和稻草覆盖对土壤团聚体组成和结合有机碳含量的影响不同,草篱主要增加2 mm水稳性团聚体含量及其结合有机碳含量,稻草覆盖增加0.25 mm水稳性团聚体含量及其结合有机碳含量。综合来看,草篱和稻草覆盖相结合对改善坡面土壤结构作用稳定。土壤有机碳含量较高时,土壤总有机碳含量与粒径2mm的大团聚体有机碳含量呈显著正相关(r=0.659);随着有机碳含量降低,土壤总有机碳含量与土壤0.25—0.053 mm和0.053 mm微小团聚体碳含量相关性逐渐增大。     

长期不同施肥方式对黄潮土肥力特征的影响

依托黄潮土35 年长期定位试验,以2种土壤物理肥力指标、8种土壤化学肥力指标和5种土壤生物肥力指标进行主成分分析,最后将各主成分得分系统进行聚类分析.结果表明: 不同施肥方式对土壤肥力指标影响显著.施用有机肥处理(M、MN、MNP、MNPK)与NPK处理相比,土壤容重显著降低,而土壤孔隙度、有机质、全氮、碱解氮、全磷、有效磷、微生物生物量和过氧化氢酶、脲酶、碱性磷酸酶活性均显著增加;通过主成分分析可将原15个土壤指标降维,提取出2个主成分,反映了原信息量的85.5%,且无原变量丢失.土壤容重、孔隙度、有机质、全氮、碱解氮、全磷、有效磷、速效钾、微生物生物量、过氧化氢酶、脲酶、碱性磷酸酶、蔗糖酶活性在第1主成分上有较高因子负荷,全钾和pH在第2主成分上有较高因子负荷;以2个主成分得分为新指标进行聚类,得到长期不同施肥方式对黄潮土的培肥效果排序为MNPK＞MNP＞M、MN＞NPK＞N、NP＞CK.可见施用有机肥对黄潮土培肥效果更显著,以有机肥配施氮磷钾化肥方式效果最优.     

垄作稻田和垄作养鱼稻田土壤结构与肥力特征研究

水稻半旱式垄作栽培技术(又称水田自然免耕技术)的推广运用为稻田资源的综合开发利用,尤其是稻田高产养鱼奠定了物质和技术基础。它比较合理地解决了传统淹水平作水稻和传统稻田养鱼中存在的种稻与蓄水,种稻与养鱼,养鱼与晒田,养鱼与化肥、农药施用,水稻与杂草,水稻与病虫等方面的问题,水稻增产显著,成鱼产量大幅度提高,一般可达750—2250kg·ha~(-1),高者3750kg·ha~(-1)以上。物质循环和能量转化的成倍增加,势必对稻田生境和土壤肥力产生影响。因此,搞清楚传统淹水平作稻田起垄后的垄作稻田和垄作养鱼稻田的土壤结构和土壤肥力的变化规律,对指导开发稻田资源,实现稻鱼双丰收具有重要的意义。     

基于主成分分析的古树土壤肥力综合评价

以广州市海珠区登记在册的40株古树为研究对象,调查其生长状况,采集土壤测定pH、EC值、容重、通气度、有机质、全N、全P、全K、水解N、有效P、速效K含量等11项理化指标,采用主成分分析和聚类分析对古树土壤肥力进行综合评价.结果表明:海珠区大多数古树土壤EC值偏低(<0.35 mS·cm-1),表现为强变异;土壤有机质...     

平衡施肥对缺磷红壤性水稻土的生态效应

为了研究平衡施肥对缺磷水稻土的生态效应,对长期缺施磷肥水稻土进行了3.5年平衡施肥试验。试验采取盆栽水稻的方式,在长期缺施磷肥的红壤性水稻土上比较不施磷肥（NK）、平衡施用氮磷钾无机肥（NPK）、无机氮磷钾肥配施硅肥（NPKSi）、无机氮磷钾肥配施有机肥（无机肥占3/5）、NPK基础上增施磷肥（NKhP）、NPKM基础上增施磷肥（NKhPM）处理的土壤肥力、土壤微生物特性、土壤磷的渗漏量以及地上部水稻产量、养分利用率、磷肥利用率的变化。试验表明,平衡施肥处理NPK、NPKSi、NPKM、NKhPM显著提高水稻产量,比不施磷肥（NK）平均增产147%,其中NPKM提高152%;能提高土壤肥力,比不施磷肥土壤有机质含量平均提高18.5%,其中NPKM提高30.1%;显著提高土壤微生物生物量,比不施磷肥土壤微生物生物量碳（MBC）平均提高57.2%,其中NPKM提高87.1%;提高氮素、钾素养分利用率,比不施磷肥平均分别提高120.3%、33.6%,其中NPKM分别提高152%、43%。而长期重施无机磷肥处理（NKhP）虽然水稻产量比不施磷肥处理提高125.1%,但因土壤中磷酸根离子含量过高影响土壤微生物正常生长,土壤微生物活度比不施磷处理降低9.4%,土壤微生物量碳（MBC）降低2.4%,稻田土壤微生物生态系统质量劣化。此外,重施磷肥处理（包括NKhP、NKhPM）易导致稻田水体的磷污染。各处理比较,NPKM综合生态效应最佳,以下依次是NKhPM、NPKSi、NPK,NKhP,NKhP对稻田土壤微生物生态系统产生负效应。根据试验结果,平衡施肥是恢复缺磷水稻土的有效措施,其中在平衡施用氮磷钾化肥的基础上增施有机肥或硅肥效果较好。     

Alleviation of Both Water and Nutrient Limitations is Necessary to Accelerate Ecological Restoration of Waste Rock Tips

Hard rock quarries are commonly located close to national parks and special areas of conservation and are generally regarded as visually intrusive. Consequently, restoration strategies that effectively accelerate natural plant regeneration processes are required. Slate waste tips present extreme conditions for plant establishment with multiple potential limiting factors (e.g., lack of organic matter, nutrients, and poor water retention). In this study, we investigated ecological strategies to accelerate natural regeneration at the largest slate quarry in Europe. A field experiment was conducted to assess ecosystem restoration using a contrasting set of native woody species. Treatments included amendments of waste tips with: polyacrylamide gel to increase water‐holding capacity; mineral fertilizer to increase nutrient supply; and two treatments that increased both (organic waste or boulder clay addition). Ecosystem recovery was evaluated through above‐ and below‐ground productivity (plant and microbial, respectively) and soil analyses. Neither increasing nutrient supply (with mineral fertilizer) nor water‐holding capacity (with polyacrylamide gel) was sufficient, alone, to improve plant establishment. However, both boulder clay and organic waste amendment significantly enhanced plant growth. There was a marked positive interaction in the effects on tree growth of the amendment with organic waste and boulder clay. Large interactions occurred between tree species and substrate amendments. The growth of N₂‐fixing species was strongly favored over non‐fixers where there was no addition of material increasing soil nitrogen supply, whereas the growth advantage of pioneer species over non‐pioneers was greatest with fertilizer, organic waste, or clay additions. Organic waste addition had the greatest positive impact on soil processes.     

毛乌素沙地沙漠化逆转过程土壤颗粒固碳效应

为揭示毛乌素沙地沙漠化逆转过程中土壤颗粒的固碳效应,选择陕北榆林治沙区从流沙地、半固定沙地到林龄为20～55年生的灌木和20～50年生的乔木固沙林地,采用物理分组法分析了土壤砂粒、粉粒、黏粒结合碳的演变特征和累积速率.结果表明: 对比流沙地,土壤总有机碳及各颗粒碳含量在两种固沙林地均呈显著增加趋势,并以表层0～5 cm土壤碳含量增幅最高.从流沙地到55年生灌木和50年生乔木固沙林地,0～5 cm土层砂粒碳密度增速均为0.05 Mg·hm^-2·a^-1,粉粒碳密度增速分别为0.05和0.08 Mg·hm^-2·a^-1,而黏粒碳密度增速分别为0.02和0.03 Mg·hm^-2·a^-1.0～20 cm土层,两种林地各颗粒碳密度增速平均为0～5 cm土层的2.1倍.按此增速到50～55年生的固沙林地时,两种林地0～20 cm土层的砂粒碳、粉粒碳和黏粒碳密度分别比流沙地平均提高6.7、18.1、4.4倍,并且颗粒碳对总有机碳的累积贡献率平均为粉粒碳(39.7%)≈砂粒碳(34.6%)>黏粒碳(25.6%).综上,毛乌素沙地沙漠化逆转过程土壤颗粒均表现出显著的固碳效应,且以砂粒和粉粒为主要固碳组分.     

东北黑土成土母质培肥过程中土壤肥力变化特征

利用已设置14年的黑土成土母质(表层以下2.0～3.0 m深)培肥定位试验,研究不同农艺措施培肥后土壤肥力指标的变化特征,结合小麦盆栽耗竭试验评估土壤供肥能力,综合评价不同农艺措施对黑土母质培肥的效应。与初始母质相比,黑土母质培肥14年后,土壤总有机碳、全氮、团聚结构稳定性和其他养分含量均不同程度提高,土壤肥力水平的高低直接影响盆栽试验中土壤对小麦的供肥能力。主成分分析发现,母质经过14年的培肥,碳投入量较大的农田秸秆还田处理和苜蓿培肥处理与表层(0～20 cm)黑土更接近,其次是农田有机肥和自然草地培肥处理,农田单施化肥和不施肥处理培肥效果最差。14年连续的外源碳输入通过改善土壤团聚结构和进入土壤的碳分解转化,影响土壤的物理和生物化学性质,促进母质土壤肥力发育。农田秸秆还田、施用有机肥和种植苜蓿对黑土母质肥力提升效果最好,是保证黑土肥力和土壤培肥的有效措施,研究结果可为东北黑土区退化土壤培肥提供理论依据和指导。     

Effects of soil erosion on crop productivity

Soil erosion and the effects of soil erosion on crop productivity have become emotional issues and have attracted the attention of agriculturists, environmentalists, and the public in general. In spite of heavy investments in research and development, the global rates of accelerated erosion are now presumbly higher than ever before. However, the data from available records obtained by diverse methods are uncomparable, unreliable, confusing, and often vary by several orders of magnitude. Reports of erosion‐caused alterations in crop productivity and soil properties are also contradictory and subjective. In addition to the lack of standardized methodology in evaluating soil erosion and its effects on crops, controversial interpretations are attributed to differences in soil profile characteristics, nutrient status, crops grown, and prevailing climatic conditions. Although erosion is generally associated wtih yield reductions, there are examples of where soil erosion has had no effect or has had a positive effect on crop production. Accelerated erosion affects productivity both directly and indirectly. Directly, the erosion‐induced reduction in crop yields is attributed to loss of rooting depth, degradation of soil structure, decrease in plant‐available water reserves, reduction in organic matter, and nutrient imbalance. Depending on soil properties and the degree of degradation, adverse effects of erosion on crop yields can be mostly compensated for by additional inputs of macronu‐trients (N, P, K) and macronutrients plus organic matter, by supplemental applications of some micronu‐trients, and by irrigation. For some soils, e.g., tropical soils, crop yields from severely eroded soils are significantly lower than those from uneroded lands and are often uneconomic in spite of additional inputs. Specific examples of yield alterations are given in relation to the loss of plant nutrients, soil water reserves, and alterations in soil properties. Criteria for soil‐loss tolerance are discussed, and productivity restoration of eroded soils is reviewed in relation to soil organic matter content and nutrient requirments. Research and development priorities are presented.