Soil–landscape variability: mapping and building detail information for soil management

The study of soil–landscape relationships at a detailed scale (1:10 000) and its use for soil management was less common in developing countries. The study was conducted in western Ethiopia with the aim to explain the soil variability across landscapes, classify soils into mapping units and produce a map of these soils. This study was performed based on a discrete model of spatial variation. Five soil reference groups: Vertisols, Cambisols, Fluvisols, Luvisols and Leptosols were identified in the study site. Distribution of the soil reference groups was determined by landscape position. Variation in soil texture, colour, pH , exchangeable acidity, organic carbon, total nitrogen, available phosphorus (av. P), carbon to nitrogen ratio (C/N), exchangeable potassium (K), calcium (Ca), magnesium (Mg), sodium (Na) and cation exchange capacity (CEC ) was observed within and among soil mapping units (SMU s). Variability was considerably high for exchangeable Ca and CEC . Factor analysis result indicated that variation in soil properties within land unit was comparatively highest in Leptosols of SMU 9 (88.87%) and lowest in Vertisols of SMU 1 (60.82%). Moderate‐to‐fine scale mapping of soil properties helps to build detail information for soil management. Grouping fields into mapping units that require more or less similar management measure would be an important soil–landscape concept. As a result, mapping units could be used as cost‐effective means of treating variable field so as to optimize the forecasted benefits.     

南方花岗岩红壤典型区土壤有机质的空间变异特征

 通过野外实地调查与室内试验,以长汀县为研究区,在GIS的支持下,运用地统计学方法分析南方花岗岩红壤典型区表层土壤有机质的空间变异特征。结果表明:研究区土壤有机质质量分数总体水平中等并具有中等的空间相关性,平均为2.73%;变异系数为72.73%,属中等变异;由空间自相关部分引起的空间变异性程度较大,C0/(C0+C)值为47.13%,变程为21.48km;在空间分布上呈现四周高中间低的分布特征,在中部地区形成连片的低值区,西部有机质质量分数整体较高,存在最高值。研究成果可为南方花岗岩红壤侵蚀退化地的生态恢复与重建提供参考。     

Maize root development and grain production as affected by soil and water management on a sandy soil in a semi-arid region of southern Mozambique

Average yield of maize (Zea mays L.) in Mozambique is low, mainly due to low use of inputs in agriculture, high seasonal rainfall variability and inadequate soil preparation. A study conducted in two summer crop seasons (November–March 2012/2013 and 2013/2014) examined the impact of three tillage methods (hand hoeing, strip tillage and conventional tillage), two fertiliser levels (0 and 40% N) and two water supply regimes (rainfed and irrigated) on maize root development and grain yield on a sandy soil in a semi-arid region of Mozambique. Tillage had a major effect on soil penetration resistance, but little effect on root growth and limited effect on yield. Thus, there appears to be little need for loosening on this soil. There was also no interaction between tillage and the other experimental factors, meaning that tillage system can be chosen irrespective of fertiliser and water supply. Irrigation had the largest impact on root and shoot growth and crop yield, increasing yield in season 2 from 670 to 4780?kg ha^–1.There was a very strong interaction between fertiliser and water supply, with no yield increase for fertiliser in the rainfed treatment, while combined with irrigation it increased yield by 1590?kg ha^–1 in season 1 and 1840?kg ha^–1 in season 2. Thus, for the conditions studied here, it was rational to add fertiliser only in combination with irrigation and not in a rainfed system.     

How good is a reconnaissance soil map for agronomic purposes?

Abstract. Information about the soil fertility status in irrigated ricelands at regional scales (1:50 000–1:250 000) is commonly not contained in classical soil maps. To assess the agronomic suitability of two different reconnaissance soil maps, we conducted a detailed soil survey in the Nueva Ecija province, Philippines. Soil samples were collected from 384 farmers' fields, and soil properties were measured for topsoil and subsoil samples. For most soil properties, a soil map made in 1940 (1:125 000) had within-map unit variances that were smaller than the total variance, whereas a new soil map of 1992 (1:50 000) did not significantly reduce the within-class variance. In both soil maps, classification into mapping units accounted for 0–40% of the variance of 14 agronomically important soil properties and large within-map unit variabilities were found. Underlying strategies of classical soil survey supported the partition of variance for relatively stable soil properties, such as soil texture, CEC, and organic matter. If reconnaissance soil maps are used in quantitative land evaluation studies, existing maps require upgrading by adding quantitative information about relevant soil properties and their within-map unit variability The sampling demand for upgrading a reconnaissance soil map was large, but pedotransfer functions can be used as cost-saving tools. Measures of soil nutrient status were highly variable within all mapping units and differences among farmers were much greater than the differences between soil types. Therefore, nutrient management in the study region should be based on individual field or farm recommendations rather than on soil-map based recommendations.     

Spatial interpolation of soil hydraulic properties and simulated rice yield

Abstract. Simulated estimates of crop yield were made for rainfed rice in a 50 ha dryland rice area. The aim was to investigate how soil units and management units of different sizes with different yields could be used to obtain values for areas of land. Two procedures were applied. First, yields were simulated at six sites, that were representative of six soil mapping units. Second, yields were simulated using soil information from 133 auger sites, and were interpolated over management units using block kriging. Differences between the two procedures for the total area and for a test set of 22 additionally sampled locations were small. A 60% increase in precision was achieved when relatively large management units were defined.
A Geographical Information System was used to identify areas with greatest yield potential for rainfed dryland rice. Statistical analysis showed that the six soil units could be grouped into three yield classes. The largest yields were obtained for a sub-area comprising 11% of the survey area which was associated with a slowly permeable Bg horizon in the soil profile.
It was concluded that the best procedure for the spatial interpolation of simulated rice yield should be based on preliminary simulation of crop yields. A sensitivity analysis of the impact of weather variability and soil heterogeneity on the variation of yield was useful to detect the importance of their contributions. The procedures developed in this study are of value in obtaining a reliable estimate of average yield, and can consequently be used for associated cost-benefit calculations.     

基于不同地表曲面模型预测土壤有机碳含量

Local terrain attributes,which are derived directly from the digital elevation model,have been widely applied in digital soil mapping.This study aimed to evaluate the mapping accuracy of soil organic carbon (SOC) concentration in 2 zones of the Heihe River in China,by combining prediction methods with local terrain attributes derived from different polynomial models.The prediction accuracy was used as a benchmark for those who may be more concerned with how accurately the variability of soil properties is modeled in practice,rather than how morphometric variables and their geomorphologic interpretations are understood and calculated.In this study,2 neighborhood types (square and circular) and 6 representative algorithms (Evans-Young,Horn,Zevenbergen-Thorne,Shary,Shi,and Florinsky algorithms) were applied.In general,35 combinations of first-and second-order derivatives were produced as candidate predictors for soil mapping using two mapping methods (i.e.,kriging with an external drift and geographically weighted regression).The results showed that appropriate local terrain attribute algorithms could better capture the spatial variation of SOC concentration in a region where soil properties are strongly influenced by the topography.Among the different combinations of first-and second-order derivatives used,there was a best combination with a more accurate estimate.For different prediction methods,the relative improvement in the two zones varied between 0.30％ and 9.68％.The SOC maps resulting from the higher-order algorithms (Zevenbergen-Thorne and Florinsky) yielded less interpolation errors.Therefore,it was concluded that the performance of predictive methods,which incorporated auxiliary variables,could be improved by attempting different terrain analysis algorithms.     

Small scale digital soil mapping in Southeastern Kenya

Digital soil mapping techniques appear to be an interesting alternative for traditional soil survey techniques. However, most applications deal with (semi-)detailed soil surveys where soil variability is determined by a limited number of soil forming factors. The question that remains is whether digital soil mapping techniques are equally suitable for exploratory or reconnaissance soil surveys in more extensive areas with limited data availability. We applied digital soil mapping in a 13,500 km² study area in Kenya with the main aim to create a reconnaissance soil map to assess clay and soil organic carbon contents in terraced maize fields. Soil spatial variability prediction was based on environmental correlation using the concepts of the soil forming factors equation. During field work, 95 composite soil samples were collected. Auxiliary spatially exhaustive data provided insight on the spatial variation of climate, land cover, topography and parent material. The final digital soil maps were elaborated using regression kriging. The variance explained by the regression kriging models was estimated as 13% and 37% for soil organic carbon and clay respectively. These results were confirmed by cross-validation and provide a significant improvement compared to the existing soil survey.     

Soil CO2 emission and its relationship to soil properties under different tillage systems

There is a lack of understanding as to which soil property is the most important at regulating the temporal variability of soil CO₂ emissions on China’s Loess Plateau. The objective of this study was to evaluate the CO₂ emissions and their relationships to certain soil properties in a winter wheat (Triticum aestivum L.) field subject to no-till (NT) and conventional tillage (CT) practices. The CO₂ emissions were signi?cantly higher in the CT (257.6 mg CO₂ m^?2 h^?1), compared with the NT (143.8 mg CO₂ m^?2 h^?1), treatment. Soil organic matter content and carbon stock were 8% and 14% higher, respectively, in the NT, compared with the CT, treatment. Regression analyses between the CO₂ emissions and soil properties, including soil temperature and carbon stock, explained up to 88% and 60% of the temporal variability in CO₂ emissions in the NT and CT treatments, respectively. Linear correlations between the soil temperature and CO₂ emissions were recorded in both the NT and CT treatments. Soil temperature was the most important factor in terms of understanding the temporal variability in CO₂ emissions in wheat fields of the study area.     

控释尿素配施黄腐酸对小麦产量及土壤养分供应的影响

【目的】 控释尿素可调控氮素缓慢释放使其与作物养分吸收速率基本同步,黄腐酸可调控土壤与肥料养分转化,两者均能显著提高肥料利用率,然而控释尿素配伍黄腐酸对小麦的协同增效研究鲜有报道。本文研究控释尿素配施黄腐酸对小麦产量和土壤肥力的影响,为其科学施用提供依据。 【方法】 以小麦 (Triticum aestivum L.) 为试材进行了盆栽试验,供试土壤为棕壤。试验设不施氮 (CK)、尿素全量 (U)、尿素减量1/3(U2/3)、尿素全量及减量配施黄腐酸 (U + FA、U2/3 + FA)、控释尿素全量及减量 (CRU、CRU2/3)、控释尿素全量和减量配施黄腐酸 (CRU + FA、CRU2/3 + FA) 共9个处理。所有处理P₂O₅ 和K₂O施入量均为150 kg/hm2和75 kg/hm2,尿素全量处理为N 225 kg/hm2,黄腐酸处理黄腐酸用量为45 kg/hm2。控释尿素处理均为一次性基施,普通尿素处理于拔节期追施尿素,基追比为1∶1。于小麦苗期、返青期、拔节期、开花期和成熟期取0—20 cm土壤样品,测定土壤硝态氮、铵态氮含量,同时测定株高和叶片SPAD值,收获期调查了小麦产量和土壤养分含量。 【结果】 1) 控释尿素CRU、CRU2/3较等氮尿素U、U2/3处理产量平均显著增加7.3%,净收益显著提高24.9%;CRU2/3与处理U产量差异不显著;CRU + FA较CRU显著增产6.4%,净收益显著增加12.6%;与U2/3处理相比,U2/3 + FA显著增产10.6%;U + FA较U处理显著减产12.8%。2) 等氮条件下,CRU、CRU2/3处理与U、U2/3处理小麦株高、叶片SPAD值差异不显著,CRU + FA、CRU2/3 + FA与CRU、CRU2/3处理间差异均不显著。3) 拔节期,CRU、CRU2/3处理土壤硝态氮含量比等氮U、U2/3处理平均显著高出54.7%,CRU2/3处理与U处理差异不显著;配施黄腐酸处理U + FA、U2/3 + FA、CRU + FA、CRU2/3 + FA的土壤有效磷含量均呈现先降低后增加最后降低的趋势,拔节期CRU处理的土壤有效磷含量与U处理无显著差异,CRU2/3、U2/3 + FA的土壤有效磷含量较CRU处理显著提高了18.6% 和20.6%;拔节期U + FA、U2/3 + FA较等氮U、U2/3处理土壤pH平均显著降低了0.11个单位,其他时期U + FA和CRU + FA处理与等量单施化肥处理差异不显著。 【结论】 控释尿素配施黄腐酸可协同增效,满足小麦各生育期氮素需求,一次性基施显著提高小麦中后期土壤养分供应强度,显著提高了小麦产量、肥料利用率和净收益。      

Spatial variability of chemical attributes of the soil,plant and yield in a pear orchard

For fruiting trees, fertilization is usually recommended based on the analyses of soil and leaves, adopting a standard value for the whole orchard. This management can lead to undesirable imbalances to the plants and local agroecosystem. Thus, this trial aimed at mapping the spatial variability of properties of soil, plant and yield in a commercial area of pears production and investigating the yield response to a distinguished fertilization. The trial was carried out in Nova Laranjeiras, Paraná, where 36 trees were selected to receive conventional fertilization (CF) and other 36 trees received a site-specific fertilization (SSF). All variables (chemical and physical attributes of soil, leaf tissue, and yield) showed some spatial dependence. For all years, yield variability was considered very high. The yield of SSF system was slightly higher (2,625 kg ha^?1) and took up a larger area (59%) when compared to SF system (2,548 kg ha^?1 at 41% area).     

麦秆还田下钾肥减量对水稻产量及钾肥利用率的影响

我国土壤缺钾程度日益加重,作物秸秆中钾素含量较高,还田后可替代部分化学钾肥,缓解土壤钾素不足。为研究秸秆还田替代钾肥的效果,本文采用田间试验方法,以常规施钾[135 kg(K2O)·hm~(-2)]处理为对照,研究了在秸秆粉碎翻压还田(6 000 kg·hm~(-2))条件下钾肥减量10%、20%、30%和40%对水稻钾素吸收累积量、水稻产量、钾肥偏生产力及经济效益的影响。结果表明:在秸秆还田的基础上,水稻植株的钾素含量和累积量随着钾肥施入量的减少而降低。钾肥施用量减少10%~40%,水稻有效穗数、每穗粒数和结实率略有降低,水稻产量和产值有所下降,钾肥减量10%、20%和30%时,对水稻产量和产值的影响不显著(P0.05)。钾肥偏生产力随着钾肥施用量的减少而提高,钾肥减量10%、20%、30%和40%处理的水稻钾肥偏生产力比不减钾处理分别提高8.4%、18.9%、33.8%和44.4%。总体而言,在常规施钾条件下,秸秆还田后随着减钾量(10%~40%)的增加,水稻钾素累积量、产量和产值均呈下降趋势,而钾肥偏生产力呈增加趋势;减钾30%以内可显著提高水稻钾肥偏生产力(P0.05),对水稻产量及产值的影响不显著(P0.05)。     

Effects of charcoal production on maize yield,chemical properties and texture of soil

The effects of charcoal production on soil textural and chemical properties were investigated in Ejura, Ghana. The aim was to study the effects of heating and charcoal residue on maize yield, soil texture and soil chemical properties. Composite samples were taken from the 0–10 cm layer of soil at charcoal-making sites and from adjacent fields (control). Twelve sites were randomly selected for the study across the range of the Kotokosu watershed. Maize was planted in four selected locations on charcoal site soils (CSS) and adjacent field soils (AFS) to assess the impact of charcoal production on crop yield. There was a significant increase in soil pH, base saturation, electrical conductivity, exchangeable Ca, Mg, K, Na and available P in the soil at the kiln sites as compared to the adjacent soils. A relative change of up to 329% was observed in K while organic C and total N decreased by 9.8% and 12.8%, respectively. Organic C and total N were highly correlated ( P <0.01) and both parameters significantly ( P <0.05) depended on clay minerals in the soils. Soil texture was also modified with a significantly higher sand content and lower clay fraction in the CSS. The grain and biomass yield of maize increased by 91% and 44%, respectively, on CSS as compared to AFS. Further research to ascertain the long-term effects of charcoal production on the soil environment and the fertility of tropical soils is needed.     

Tillage and mulch effects on productivity and water use of pea and soil carbon stocks

Soil management can notably influence crop production under rainfed farming; however, improper soil management is one of the key factors threatening sustainability. The objective of this 3 years’ study was to evaluate the performance of two types of tillage: conventional tillage (CT) and zero tillage (ZT) systems with four mulches; paddy straw mulch (PSM), maize stubble (MS), Imperata cylendrica (thatch grass, TG) and no mulch (NM) on yield and water use of pea (Pisum sativum) and physico-chemical properties of soil. CT and PSM have registered 11.1% and 36.1% higher pod yield, 10.0% and 40% improvement of water use efficiency (WUE) and 9.7% and 49.2% better harvest monetary benefit (HMB) over ZT and NM, respectively. Soil moisture content (SMC) was higher with ZT than CT. Placement of mulch has considerably higher SMC on upper soil layer over NM, but at deeper depth, there was no such evidence. The soil organic carbon (SOC) was considerably improved by 4.1% with ZT than CT, whereas, MS improved SOC by 1.9% than NM. The findings clearly suggested that CT along with PSM registered improvement in pod yield, WUE and HMB, but ZT and MS improved SOC at different soil depths and responded to carbon stock management.     

Portable soil test laboratory results compared to standard soil test values

Abstract

Results from a commercially available portable soil test laboratory were compared to standard soil test procedures used by a public soil testing laboratory. Standard soil tests examined were water extracted NO₃‐N, pH, Acid‐P, NaHCO₃‐P, and ammonium acetate extracted K. Approximately 35 to 55 different soils were used to compare methods for each soil test. Linear regression equations between the portable laboratory soil test values and those from the standard procedures were developed. The r² values for NO₃‐N, pH, Acid‐P, NaHCO₃‐P, and K were 0.970, 0.891, 0.734, 0.742, and 0.887, respectively. The coefficient of variability values for NO₃‐N, pH, Acid‐P, NaHCO₃‐P, and K were 10, 1, 13, 15, and 6%, respectively for the portable laboratory, and 9, 2, 8, 9, and 5%, respectively for the public soil testing laboratory. Multiple regression was used to relate soil properties to soil test results. The R2 values for NO3‐N, pH, Acid‐P, NaHCO₃‐P, and K were 0.970, 0.911, 0.860, 0.940, and 0.936, respectively.     

红壤调理剂的改土培肥及作物增产研究

在南方红壤地区,土壤酸化加剧、养分贫瘠化严重,研发红壤改良的技术和物化产品,对作物均衡增产和红壤可持续利用有重要意义。红壤旱地连续3年定位种植油菜-花生,花生品种为赣花5号,油菜品种为丰油730。调理剂为自行研制的专利产品,已经实现了产业化。研究了红壤调理剂对土壤微结构、物理性状、养分和pH值的影响,并对花生、油菜的产量进行了分析。结果表明:1)施用调理剂后,从微观结构来看,红壤的致密性降低、孔隙度增加,土壤颗粒直径4μm;2)施用调理剂的土壤容重显著降低,孔隙度增加到59%以上,大颗粒水稳性团聚体(0.25 mm)含量增加幅度为1.6%~14.0%,分形维数显著降低,并且与0.25mm粒径的团粒结构含量间呈极显著线性相关;3)施用调理剂的土壤电导率、有机碳、矿质态氮、有效磷、速效钾含量均提高,提高幅度在4.3%~143.7%之间;4)施用调理剂还降低了红壤的酸性,pH值从对照处理的5.28提高到5.82,差异显著;5)施用调理剂,花生和油菜增产幅度分别在13.1%~24.8%、10.3%~21.6%之间;6)应用笔者研制的红壤调理剂,可有效改善红壤旱地的理化性质,提高油菜和花生产量,其用量在2 250~3 000 kg/hm~2时较佳。     

土壤改良剂对冷浸田土壤特性和水稻群体质量的影响

以南方典型冷浸田为研究对象, 在明沟排水的基础上, 通过田间定位试验, 以不施土壤改良剂为对照, 研究了施用不同土壤改良剂(自研的脱硫灰改良剂、生物活性炭, 市售的土壤改良剂石灰、硅钙肥、腐植酸)对冷浸田氧化还原电位、土壤呼吸强度、土壤微生物数量、水稻群体构建及产量构成因素的影响。结果表明, 施用改良剂能够改善土壤理化性状, 提升土壤速效养分和pH,但除脱硫灰处理外, 其他改良剂处理对土壤Eh未产生显著影响。施用不同土壤改良剂在水稻各生育期均能有效增强土壤微生物呼吸强度和放线菌数量, 并且放线菌数量达到差异性显著水平(P<0.05), 生物活性炭处理下土壤呼吸强度和放线菌数量分别较对照增加67.6%和127.6%。各土壤改良剂处理与CK相比较均有助于提高叶片SPAD、茎蘖数、水稻干物质积累量、成穗数、穗粒数、产量结实率和根系伤流速率。其中以脱硫灰和生物活性炭处理改良效果最佳, 抽穗后29 d时,根系伤流速率较CK分别提高45.4%和39.1%, 叶片SPAD分别增加27.4%和22.5%; 成熟期水稻成穗数较对照提高12.1%和10.7%,干物质积累量增加68.8%和50.5%,产量分别增加12.8%和10.3%。综上所述, 土壤改良剂可有效改善冷浸田土壤特性及水稻群体质量, 脱硫灰和生物活性炭处理的改良效果最明显, 增产幅度最大。     

不同有机无机肥配比对冷浸田土壤肥力及水稻生长的影响

为了消减冷浸型中低产田长期浸渍、泥温低、土壤有效养分低等障碍因子,通过田间小区试验和动态取样与室内测定,研究了不同有机无机肥配比对冷浸田土壤肥力及水稻生长的影响。结果表明:与复合肥处理比较,复合肥与40%(N)生鸡粪配施处理的土壤磷酸铁盐和磷酸钙盐含量分别提高11%和17%,复合肥与60%(N)生鸡粪配施处理的土壤磷酸铝盐含量提高44%,且磷酸铝盐、磷酸铁盐和磷酸钙盐占无机磷总量的比例提高,闭蓄态磷占无机磷总量的比例降低,促使土壤中难溶性磷向易溶性磷转化,提高土壤有效磷含量;复合肥配施60%(N)生鸡粪处理的土壤松结态腐殖质占重组腐殖质的比例提高1.9个百分点,紧结态腐殖质占重组腐殖质的比例降低4.6个百分点,土壤活性有机质含量提高14%,土壤阳离子交换量提高11%;复合肥与40%(N)生鸡粪配施处理的土壤真菌和放线菌数量分别提高33%和28%,复合肥配施60%(N)生鸡粪处理的土壤细菌数和微生物活性分别提高160%和19%,水稻磷、钾吸收量分别提高5%和111%;复合肥与40%(N)生鸡粪配施处理的早、晚稻产量分别增加8%和42%,复合肥与60%(N)生鸡粪配施处理的早、晚稻产量分别增加6%和31%。有机无机平衡施肥是适合于冷浸田水稻增产的施肥方式。     

Rice yield nutrient uptake as affected by cyanobacteria soil amendments—a pot experiment

Rice production and cyanobacterial N in acid soil can be improved by liming. There is evidence that the organic amendments can increase the soil pH. The aim of this study was to find appropriate combination of soil amendments and cyanobacteria capable for enhancing nutrient uptake and improving rice yield in acidic paddy soil. Three soil amendments (rice straw, sewage‐sludge composts, NPK) with and without inoculation of cyanobacteria were studied for rice plants (Oryza sativa L.) in a pot experiment. The sludge compost had significantly reduced soil acidity from 5.44 to 6.67. The plant N and K uptake increased significantly with sludge and cyanobacteria application. The yield components increased significantly with sludge, but decreased thereafter, an exception was the number of panicles, with straw compost. These characters were also significantly affected by inoculation with cyanobacteria except 100‐grain weight, filled‐grain percentage, and harvest index. The combination of sludge compost and cyanobacteria improved the yield components and consequently grain yield (138 g pot^–1) compared with sludge treatment only (132 g pot^–1). The amount of cyanobacterial N absorbed (N‐difference method) by rice plant under sludge compost was higher than that of soils amended with either rice straw or NPK treatments. Therefore, the addition of sewage sludge to acid paddy soil not only amended the soil properties but also activated the cyanobacteria and consequently improved rice plant nutrition and grain yield.     

Nitrogen fertilization and cropping system impacts on soil properties and their relationship to crop yield in the central Corn Belt, USA

Evaluating the effects of management practices on soil physical and chemical properties would be valuable to explain field-level variability in crop production. A 23-year-old experiment on a Muscatune soil (fine-silty, mixed, superactive, mesic, Aquic Argiudolls) in Illinois with five N rates [0 (N₀), 70 (N₁), 140 (N₂), 210 (N₃) and 280 (N₄) kg N ha⁻¹] and two cropping systems [continuous corn (Zea mays L.) (CC), and corn–soybean (Glycine max (L.) Merr.) rotation (CS)] was evaluated. Specific objectives were to: (i) evaluate the effects of long-term N fertilization and cropping systems on field level changes in soil physical and chemical properties and crop yield, (ii) identify the most responsive soil physical and chemical properties to N fertilizer and crop management, and (iii) investigate the relationship between the selected soil properties and crop yield. Soil was collected in May 2004 to 30 cm depth and 20 soil physical and chemical properties were measured. The univariate analysis indicated that 14 soil properties were significantly influenced by at least one treatment effect (crops, N or crops × N). Due to multicollinearity among soil properties, principal component analysis (PCA) was used to group correlated properties, resulting in five soil properties such as soil organic carbon stock (OC stock), mean weight diameter (MWD), soil C:N ratio, exchangeable potassium (K⁺) and gravimetric moisture content (ω). Finally, the multiple regression analysis performed between PCA derived soil properties and corn and soybean yields retained all the representative soil properties from PCA except ω as yield predictors for corn (P < 0.001, R² = 0.39) from CC system, whereas none of the soil properties were significantly related to corn and soybean yields from CS system. The soil properties most influenced by long-term N fertilization of continuous corn were successfully identified with PCA and multiple regression. The insignificant relationship between corn and soybean yields from CS system and PCA derived soil properties might be due to the lack of response of soybean to N fertilization. This study shows the integrated use of multivariate and regression analyses in identifying yield determining soil properties by eliminating the multicollinearity among soil properties.     

河南省玉米施肥效应对基础地力的响应

[目的]整理2005 2013年在河南省布置的885个玉米“3414”田间试验,分析不同地力水平下玉米施肥后的增产效果、经济效益及氮、磷、钾肥利用效率,明确不同地力水平下河南省玉米施肥效应,为科学施肥提供理论依据。[方法]选取其中5个处理CK(N0P0K0)、N(N0P2K2)、P(N2P0K2)、K(N2P2K0)和NPK(N2P2K2)的试验结果。按CK处理产量将供试885个试验地土壤基础地力划分为<4 t/hm^2、4~6 t/hm^2、6~8t/hm^2、>8 t/hm^2四个水平,收集了玉米施用氮、磷、钾肥的增产量、增产率、产值、施肥成本、施肥利润和产投比,计算了各施肥处理的农学效率、偏生产力、肥料贡献率、地力贡献率。[结果]四个地力水平的试验地样本量分别占总样本的15.35%、49.42%、29.42%、5.81%。NPK处理的增产量在四个地力水平下依次为3.04、2.49、1.88和1.12 t/hm^2,且各地力水平间差异显著。增产率表现出和增产量一样的变化趋势,且下降趋势更明显。基础地力产量<4 t/hm^2时,NPK处理的增产率平均达93.23%,而基础地力产量>8 t/hm^2仅为14.44%。在施肥经济效益方面,各施肥处理的产值、施肥利润及产投比均随地力水平的提高而升高,各地力水平间差异显著。其中NPK处理的产值、施肥利润及产投比在地力产量<4 t/hm^2时分别为10238元/hm^2、8862元/hm^2和5.75,在基础地力产量>8 t/hm^2时分别为15407元/hm^2、13736元/hm^2和8.05。河南省土壤地力对玉米产量的贡献率平均为69.99%,各地力水平下的地力贡献率随地力水平的提高而显著提高,四个地力水平的地力贡献率平均依次为53.24%、67.68%、78.80%和86.63%。土壤氮素、磷素、钾素地力贡献率平均分别为78.32%(40.72%~100%)、88.47%(70.40%~100%)、90.02%(78.27%~99.31%),总体以钾地力贡献率最大,磷地力贡献率次之,氮地力贡献率最小。从地力水平变化的角度来看,氮素、磷素、钾素地力贡献率均随地力水平的提高而逐渐增高,其中各地力水平下土壤氮素的地力贡献率分别为65.08%(<4 t/hm^2)、77.04%(4~6 t/hm^2)、85.32%(6~8 t/hm^2)、90.47%(>8 t/hm^2)。不同地力水平下各施肥处理的偏生产力随地力水平的提高而显著升高,农学效率和肥料贡献率总体随地力水平的提高而下降,说明提高基础地力可降低玉米产量对外源肥料的依赖性。[结论]提高土壤基础地力能够促进玉米增产、增收,降低玉米对外源肥料的依赖。河南省玉米生产中应重视土壤培肥,并根据不同地力水平合理施肥以保证玉米高产稳产、提高养分利用效率、节本增收。