控释肥料的大蒜肥效研究

对控释肥料(CRFs)的大蒜肥效进行了田间试验,结果表明:控释肥料与普通肥料(OFs)相比,在肥料施用量低和中等时具有提高肥效、增加产量的作用,大蒜的生物量分别增加80.5%和51.1%,蒜苔和蒜头产量分别增加180%、100%、和69.2%、29.3%,而高用量时产量反而降低;在比普通肥料(300kg/hm2)减少一半用量的情况下,控释肥料(150kg/hm2)处理的大蒜生物量、蒜苔和蒜头产量分别增加15.6%、61.5%和11.6%。经过大蒜的整个生长季,控释肥料处理的根际土壤有效养分仍能维持较高的水平,控释肥料能显著提高大蒜体内的氮磷钾含量及肥料的养分利用率。     

Long‐term changes in the floristic composition and soil characteristics of reclaimed sodic land during eco‐restoration

The study was conducted under the “Uttar Pradesh Sodic Lands Reclamation Project” to examine changes that occurred in the reclaimed sodic land in two districts of Uttar Pradesh, India. The study focuses on long‐term seasonal changes in the floral diversity and soil characteristics of the reclaimed sodic land over a period of 10 y. The changes in the floristic composition, plant density, and soil characteristics (microbial biomass carbon [MBC], pH, exchangeable‐sodium percentage (ESP), and electrical conductivity) were compared among the different study plots after different years of sodic‐land reclamation. The study plots comprised reclaimed land with rice–wheat cultivation; semireclaimed land under rice cultivation only and nonreclaimed barren sodic land. There was a significant variation in the floristic composition of the three study plots. Dominance in the floristic composition was shifted from monocotyledonous weeds in the nonreclaimed sodic land to dicotyledonous weeds in the reclaimed land after 10 y of reclamation. Among the soil characteristics, the most remarkable changes were observed in soil MBC and ESP during the course of sodic‐land reclamation. Soil MBC increased up to 480% and ESP values decreased up to 79% in the reclaimed plots with reference to the nonreclaimed plots. The soil amelioration was more pronounced in the upper layer (0–30 cm) as compared to the lower layer (below 30 cm depth). A positive significant correlation was revealed between soil MBC and floristic composition of the reclaimed plots. These changes in floristic composition and soil characteristics could be used as good indicators of the eco‐restoration of the sodic lands. The present study provides useful insights in understanding the temporal progress of eco‐restoration in the reclaimed sodic lands.     

Impact of fertilization on cover crops and microbial community on a bauxite‐mined soil undergoing reclamation

The reclamation of bauxite‐mined areas can be favored by the application of organic and/or chemical fertilization to restore the vegetation. Otherwise, the impact of fertilizations on soil microbiota or plant–microbe interactions as land reclamation progresses is less understood. To address this issue, we evaluated the impact of organic and chemical fertilization on plants and soil microbial community within the first 36 months of land reclamation in a bauxite‐mined site. The experiment was set up according to a split‐plot design in which the main plots received fertilizations [non‐fertilized control (NF), chemical fertilization (CF; NPK and rock phosphate), organic fertilization (OF; poultry litter), and CF+OF combined], and the subplots received cover crops [no cover crops (NC), grass (B; Brachiaria), legume (S, Stylosanthes), and B+S combined]. Cover crops biomass yield was assessed annually with five field campaigns per year. We used phospholipid fatty acids (PLFAs) to infer the impacts of mining and restoration practices on actinobacteria, Gram‐negative and Gram‐positive bacteria, arbuscular mycorrhizal fungi, and fungi. Accordingly, PLFAs were determined before bauxite mining (pre‐mining), six months after topsoil reconfiguration (post‐mining), and after 14 and 36 months following the application of the fertilizations and cover crops. PLFAs results indicated that in post‐mining, the living microbiota was significantly lower than in pre‐mining. Cover crops biomass yield was highest for B and B+S fertilized with CF+OF at 14 and 36 months. Both parametric and non‐parametric statistics showed a temporal variation in the response of living microbes to the treatments applied. After 14 months, living microbes showed greatest response to OF, while at 36 months their response was strongest in the treatments with highest plant biomass production (B and B+S). These results suggest that in the early stages of land reclamation, living microbial biomass benefit the most from organic fertilizers. As this initial boost decline, living microbes are more likely to thrive in areas undergoing reclamation where they can develop synergistic interactions with plants.     

早稻施氮对连作晚稻产量和氮肥利用率及土壤有效氮含量的影响

于20022～005年,在湖南长沙采用连续定位试验,研究了早稻施氮对连作晚稻产量、氮肥利用率、土壤有效氮含量的影响。试验设早稻施氮/晚稻不施氮、早稻施氮/晚稻施氮、早稻不施氮/晚稻不施氮、早稻不施氮/晚稻施氮4个处理。结果表明,在连续4年早季施氮的条件下,连作晚稻施氮处理的平均产量为6.45.t/hm2,地上部干物质重12.13.t/hm2,氮素吸收量183.6.kg/hm2,分别比连作晚稻不施氮处理增加28.4%、35.1%和103.5%,均达到显著水平;在连续4年早季不施氮的条件下,连作晚稻施氮处理的平均产量为6.61.t/hm2,地上部干物质重12.14.t/hm2,氮素吸收量165.6.kg/hm2,分别比不施氮处理增加33.4%、37.6%和95.6%,均亦达到显著水平。连作晚稻在早季不施氮和早季施氮两种情况下氮肥利用率不同,前者的氮肥生理利用率显著高于后者,增幅为37.8%,两者的氮肥农学利用效率、吸收利用率差异不显著,但前者4年氮肥农学利用效率平均值比后者高18.1%,吸收利用率低6.8个百分点。早晚两季均不施氮小区土壤碱解氮含量均明显低于其他施氮小区,但没有出现随试验年度加长而连续下降的趋势;当早稻或晚稻其中有一季施用了氮肥,或者两季均施用了氮肥的小区,土壤碱解氮含量差异不显著。说明连作晚稻产量主要受当季施氮量的影响,而受早季施氮量的影响较小;早季不施氮小区的连作晚稻氮肥的农学利用效率、生理利用率比早季施氮小区高;在一定程度上降低稻田氮肥用量不会导致土壤背景氮含量的下降。     

USE OF RESERVOIR DEPOSITS AND CAESIUM-137 MEASUREMENTS TO INVESTIGATE THE EROSIONAL RESPONSE OF A SMALL DRAINAGE BASIN IN THE ROLLING LOESS PLATEAU REGION OF CHINA

This paper reports the results of an investigation of the erosional response of the 3·86 km² Zhaojia Gully catchment in the rolling loess plateau region of Zichan County, Shaanxi Province, China. In the absence of direct measurements, information derived from reservoir deposits and from caesium-137 measurements on both the catchment soils and reservoir deposits was used to obtain a retrospective assessment of the longer-term (ca. 30 year) erosional response of the catchment and of the relative contributions of the rolling plateau surface and the gully areas to the sediment output from the basin. Net erosion rates on cultivated land occupying the gentle crest slopes and steeper lower slopes of the rolling plateau and the steep gully slopes were estimated to be 4500 t km⁻² year⁻¹, 8584 t km⁻² year⁻¹ and 15851 t km⁻² year⁻¹, respectively. Estimates of annual sediment yield from the study catchment based on analysis of sediment deposits in the two sediment-trap reservoirs ranged between 4627 and 32472 t km⁻² year⁻¹. Almost all the sediment transported from the catchment was contributed by 2–4 large floods each year. Measurements of the caesium-137 content of recent sediment deposits in a sediment-trap reservoir allowed the relative contributions of the total sediment yield derived from the rolling plateau and gully areas of the catchment to be estimated at 23 and 77 per cent, respectively. Analysis of the sediment deposits dating from 1973–1977 in another sediment trap reservoir allowed individual flood event couplets to be identified and indicated that the sediment associated with the first one or two floods in a season, when the soils of the plateau area were relatively dry, was derived primarily from the gully areas. The cultivated soils of the rolling plateau contributed an increased proportion of the total sediment yield during the latter stages of the flood season when the soils were wetter, and surface runoff and erosion were more widespread. Based on analysis of the caesium-137 content of the sediment deposited in this sediment-trap reservoir, the relative contributions of sediment from the rolling plateau and gully areas over the period 1973–1977 were estimated to be 21 and 79 per cent, respectively. The results obtained demonstrate the potential for using caesium-137 measurements and analysis of reservoir deposits to document the erosional response of a drainage basin. © 1997 John Wiley & Sons, Ltd.     

Gypsum and water management interactions for revegetation and productivity improvement of brackish marsh in Louisiana

Abstract

A field study evaluating the effects of gypsum and water management on the survival, yield, and protein content of selected species of marsh vegetation was conducted on an open area inundated by brackish water near Hackberry, Cameron Parish, Louisiana. The overall growth and yield response of four species of marsh vegetation: joint grass (Paspalum vaginatum SW.), marsh hay cordgrass (Spartina patens Muh L.), salt grass (Distichlis spicata L.), and American three square (Scirpus americanus Pers.) to gypsum addition (0 versus 7 Mg/ha) and water management (flooded versus non‐flooded plots) were statistically evaluated.

Soil drying was detrimental to the overall growth and yield of all marsh vegetation. There was zero plant survival in the non‐flooded plots except the marsh hay cordgrass with a survival rate of 32.8 %.

Plots receiving 7 Mg gypsum/ha had significantly higher dry matter production than the control. Gypsum application increased dry yield of joint grass (5.44 to 8.08 Mg/ha), marsh hay cordgrass (1.90 to 6.91 Mg/ha), salt grass (0.97 to 2.79 Mg/ha) and three‐square (1.55 to 2.84 Mg/ha) in flooded plots. The yield of marsh hay cordgrass, the only surviving species in the non‐flooded plots, produced a yield increase of 0.40 Mg/ha in response to gypsum. Significantly higher survival rates were observed in flooded plots treated with gypsum than in the non‐flooded plots receiving no gypsum. The mean survival rate for the gypsum‐ treated plots was 68.2%, as opposed to 21.9% for the untreated plots.     

莲花湖库区水源涵养林林地产流产沙分析

对莲花湖库区主要植被类型红松林、兴安落叶松林、杂木林和荒草地土壤物理性状及渗透性能进行了研究，结果表明，各林型土壤最大蓄水量依次为落叶松林〉杂木林〉红松林〉荒草地；土壤非毛管蓄水量依次为落叶松林〉红松林〉杂木林〉荒草地。林地土壤初渗速率和稳渗速率均显著高于荒草地。以坡面径流观测场为观测手段，分析了4个径流小区产流产沙与降雨因子的相关关系，结果表明，场降雨产流量和产沙量与降雨量和雨强均呈良好的相关关系。林地与荒草地的降雨产流产沙差异显著，说明林地具有较好的保持水土功能。     

黄河泥沙充填复垦中土工布排水拦沙效果的模拟试验

为验证土工布用于加速引黄河泥沙充填采煤沉陷地的后期侧向排水及降低排水中泥沙含量的效果,在室内进行了基于土工布的泥沙充填排水模拟试验。该试验在玻璃槽内完成,设计3个试验处理,分别为ZT-250(整个断面开口+铁丝网+ZW-250土工布)、ZT-300(整个断面开口+铁丝网+ZW-300土工布)以及CK(断面中间部分开口+可调节高度的塑料板)。测定了3个处理的排水含沙量及泥沙粒径、玻璃槽内表层泥沙粒径以及充填表层和底层泥沙含水率随时间的变化。结果表明:1)3种处理排水含沙量整体差异较小,但使用土工布处理的排水含沙量随时间的延长逐渐降低,而对照处理排水含沙量随时间的延长逐渐增大;2)排水初期和中期,对照CK的排水中泥沙的黏粒含量均高于使用土工布的2个处理。排水后期CK的黏粒含量介于处理ZT-250和ZT-300之间。随着试验的进行,使用土工布的2个处理排水中泥沙的黏粒含量逐渐升高,粉粒含量逐渐降低,而对照处理呈现相反的变化趋势。使用土工布的2个处理拦沙效果较为稳定。3)3种处理充填表层泥沙粒径级配无明显差异,但使用土工布处理充填的表层泥沙的极细砂粒含量较高。4)3种处理充填泥沙表层和底层含水率变化存在差异,使用土工布可以加速泥沙中过饱和水的排除,其中处理ZT-250排水效果最好。该研究可为中国东部高潜水位平原矿区采煤沉陷地引黄河泥沙充填复垦的快速排水工艺革新提供依据。     

Assessment of soil microbial communities in surface applied mixtures of Illinois River sediments and biosolids

Restoration of the Illinois River and its backwater lakes involves the dredging of millions of cubic meters of sediment, and the relocation of this dredged sediment is a significant challenge. Beneficial use of sediment as landscaping soil on brownfields, strip mines, highway borders and other areas is a potential use for large quantities of this material, as sediments have desirable soil characteristics, including a favorable texture for plant growth and good water holding capacity. The addition of biosolids to Illinois River sediments has the potential to increase the organic and nutrient content of the sediments and thus to make these sediments more useful for the reclamation of damaged soils. The goal of the current study was to assess the impacts of biosolids additions on the physical/chemical characteristics and microbial communities of surface applied river sediments. Field plots containing various sediment/biosolids mixture were established and examined 1 year after application. Results indicated that biosolids addition had significant positive effects on soil organic carbon, total Kjeldahl nitrogen, total phosphorous, and microbial biomass and activity. In addition, the sediment/biosolids mixtures showed lower salinity and lower concentrations of copper, lead and zinc than the pure biosolids. PLFA analysis revealed that biosolids addition resulted in shifts in microbial community composition, with relative increases in Gram negative bacteria and relative decreases in Gram positive bacteria, fungi, and actinomycetes. These data suggest that a mixture of sediment and biosolids is preferable to either sediment or biosolids alone.     

近50年沂蒙山区两个不同岩性小流域塘库的拦沙效应

在沂蒙山区选取代表性花岗岩与石灰岩小流域各一处,即分别为姜庄和泉安子小流域,对比分析了两个不同岩性小流域塘库近50年的拦沙效应。沿主沟道方向于两个塘库中央位置各取3孔沉积物样芯,参照流域人类活动和环境演变历史,探明了各孔137 Cs、210 Pbex、黏粒和容重深度分布变化特征。以137 Cs和210Pbex示踪法进行沉积物断代,参照塘库原始库容曲线,计算建坝以来塘库不同时段的年均淤沙量,以表征拦沙效应。姜庄和泉安子塘库各孔、各时段拦沙效应的计算结果分别为(394±142)~(121±43)t/a和(22±7)~(59±21)t/a,平均值分别为(208±75),(41±15)t/a,建库以来的总拦沙量分别为10 475,2 097t。姜庄塘库拦沙效应明显大于泉安子塘库,这是此两座塘库分别控制的花岗岩与石灰岩小流域在人类扰动作用下产沙强度的差异所致。近50年两个塘库拦沙效应的变化趋势反映了不同岩性小流域人类活动及其产沙强度响应的近期特征和规律。     

基于Hydrus-1D的黄河泥沙充填复垦土壤夹层结构优化

中国东部矿区煤粮复合区面积大,因采煤沉陷积水,导致大面积的耕地破坏,采煤沉陷地复垦成为中国亟待解决的问题,黄河泥沙夹层式充填复垦技术对实现采煤沉陷地复垦具有积极意义.为优化黄河泥沙充填复垦夹层式土壤剖面设计,该研究采用Hydrus-1D模拟分析了在充填复垦土壤总厚度一定的情况下,不同夹层厚度、位置和数量对重构土壤入渗和...     

Soil erosion and hydrological response to land abandonment in a central inland area of Portugal

This paper analyses the effects of land abandonment on runoff and sediment yield in a central inland area of Portugal. Rainfall simulation experiments were performed in areas of traditional land use (land cultivated with cereals) with various types of soil plant cover associated with the period of abandonment (4–5 years, 15–20 years and 30–40 years) in two different seasons, namely under very dry conditions and after a long wet period. Statistical analysis showed a notable difference between the cultivated soils and those abandoned for a long period of time, which included appreciable vegetation recovery, higher organic matter content and negligible overland flow and soil loss. Cereal cultivation, in particular ploughing, is a very negative land management practice, due to the high runoff and soil loss. Within 4–5 years a crust develops over abandoned soils with sparse herbaceous plant cover, particularly after a dry season, which enhances runoff and sediment yield. In scrubland and oak plots, although marked water repellency was registered at the end of a dry, warm season, its influence seems to be irrelevant in terms of overland flow and erosion yield. The major factor in controlling overland flow and reducing soil erosion rates appears to be the role played by vegetation in protecting the soil surface and supplying organic carbon to the top layer. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of Soil Erosion on Spring Barley Growth in East Anglia,England：Preliminary Results

The effect of soil erosion on spring barley growth was studied on a deep loamy soil in East Anglia,England,in 1992,Soil erosion was simulated by three levels of soil desurfacing,7.5,18and 30cm with three replicates.Significant differences in crop height,ground cover and crop yield were observed between the three levels of desurfacing.Soil desurfacing also has a singnificant effect on soil moisture at the 20cm depth.The interaction between soil removal and crop performance affected soil moisture at the depths of 50 and 100cm,No significant differences were found in runoff and sediment etween the three topsoil removals due to very dry growing season.Regression equations were developed between spring barley yield and soil desurfacing Spring barley grain yield declined by 97.6kg/ha per cm soil desurfacing.     

Effect of different tillage methods on maize growth on a tropical inceptisol with impeded drainage

Two trials to compare the effect of coventional, minimum and zero tillage on maize growth on a lowland tropical clay soil with impeded drainage were carried out during the rainy season of 1980 in Trinidad. During the first trial where low levels of nitrogen (50 kg/ha) and grass mulch (2 t/ha) were used, the mean fresh weight yield of ears from conventional tillage was 5.64 t/ha. Zero and minimum tillage treatments yielded about 40% less. Conventional tillage also produced significantly taller plants and more stem and leave dry matter (P = 0.05) than the other two tillage methods. The growth and yield of maize resulting from minimum and zero tillage were not significantly different.During the second trial where rainfall was heavy and higher levels of nitrogen (85 kg/ha) and grass mulch (6 t/ha) were used, seedling emergence was reduced but yields were at least 100% higher than those from the first trial and the fresh weight yield of ears from zero tillage was only 19% less than conventional tillage. Yields from zero tillage plots which had been tilled conventionally for the previous trial were only 1% higher than yields from continuous zero tillage. This improved performance of the zero tillage treatment indicates its potential for maize production on this fine textured soil and suggests the need for further studies with accompanying economic analysis.     

Afforestation effects on soil carbon stocks of low productivity grassland in New Zealand

Soil carbon stock change between two major land uses in New Zealand was measured by sampling paired plots across the boundaries of low productivity grassland and forest planted pre‐1990. The national soil carbon monitoring system uses low productivity grassland as a benchmark to evaluate soil carbon stock change for other land uses. The goal was to validate earlier estimates of the effect of pre‐1990 afforestation and to reduce their level of uncertainty. We selected a set of sites to represent the national stocks of forests planted pre‐1990. Previous studies derived estimates of the land‐use effect on soil carbon for afforestation ranging from +1.6 to ?8.5 t/ha to 30 cm depth. For all estimates, the 95% confidence interval spanned zero. Our study used nine of the previous paired‐plot sites and sampled and analysed 21 new sites. The land‐use effect of change from grassland to forest planted pre‐1990 was estimated at ?17.4 t/ha. The 95% confidence interval ranged from ?10.1 to ?24.6 t/ha and did not include zero change. The result supported the soil carbon monitoring system assumption that forests planted pre‐1990 have significantly lower soil carbon stocks than the low‐productivity‐grassland standard. Evidence of stock change occurred in depth increments to 0.2 m but with no significant change for the 0.2–0.3 m increment. This suggests that the sampling depth of 0.3 m was adequate for the estimation of soil carbon stock change.     

喀斯特地区坡面径流对产沙的影响

贵州省关岭县蚂蝗田小流域属典型喀斯特流域,根据小流域2009—2012年6个坡面径流小区的定位观测资料,研究了乔木林（黄花梨）、灌木林（女贞）、撂荒草地三种不同植被类型下坡面径流对产沙的影响。结果表明:三种植被类型的产流次数相同,但产沙次数存在较大差异,表现为荒草地 > 乔木林 > 灌木林;灌木林与乔木林的年均径流量相差不大,荒草地的年均径流量是它们总和的2倍;荒草地的年均产沙量最大,为55.17 t/km²,是灌木林的11倍,乔木林的6倍;乔木林的产流量与产沙量无明显相关关系;灌木林表现出线性关系,拟合方程为y=0.1707x+0.2526,R²值为0.48;荒草地表现为幂函数关系,拟合方程为y=0.3246x^1.2965,R²值为0.64。     

旱季雨季对黄土丘陵退耕区植被根系分布及水分利用的影响

黄土丘陵区属于季节性干旱的区域,研究退耕生态系统植被根系分布及其水分利用特征对植被恢复具有重要意义。该研究利用稳定同位素技术,采集黄土区5种典型退耕植被群落的根系、土壤样品,分析根系形态结构和稳定同位素特征,探讨根系在不同季节的吸水策略。结果显示:旱季茵陈蒿、铁杆蒿、白羊草、达乌里胡枝子群落和油松的根长密度(16.3、21.7、17.3、17.3、6.0 mm/cm3)分别是雨季(1.7、2.1、3.2、5.9、4.2 mm/cm3)的9.4、10.2、5.3、2.9、1.4倍,茵陈蒿、铁杆蒿、白羊草根系对土壤水分季节变化的响应较为敏感。茵陈蒿群落仅可利用0~10 cm土壤水,旱季铁杆蒿、白羊草群落主要利用30~40 cm土壤深度的水分,雨季吸水深度上移至0~20 cm。旱季达乌里胡枝子和油松主要利用60 cm以下的土壤水分,雨季则吸收20~40 cm土壤水分。表明退耕植被群落根系在不同季节的吸水策略不同,旱季吸收较深的土壤水而雨季则吸收近地表的土壤水,吸水深度范围的季节变化与土壤水和根系分布变化相一致。该研究为黄土丘陵区退耕植被对流域生态水文过程影响的研究提供科学依据。     

Long‐Term Integrated Nutrient Management for Rice‐Based Cropping Pattern: Effect on Growth,Yield, Nutrient Uptake,Nutrient Balance Sheet,and Soil Fertility

Abstract

A 7‐year‐long field trial was conducted on integrated nutrient management for a dry season rice (Boro)–green manure (GM)–wet season rice (T. Aman) cropping system at the Bangladesh Rice Research Institute Farm, Gazipur during 1993–1999. Five packages of inorganic fertilizers, cow dung (CD), and GM dhaincha (Sesbania aculeata) were evaluated for immediate and residual effect on crop productivity, nutrient uptake, soil‐nutrient balance sheet, and soil‐fertility status. Plant height, active tiller production, and grain and straw yields were significantly increased as a result of the application of inorganic fertilizer and organic manure. Usually, the soil‐test‐based (STB) fertilizer doses for a high‐yield goal produced the highest grain yield of 6.39 t ha^?1 (average of 7 years) in Boro rice. Application of CD at the rate of 5 t ha^?1 (oven‐dry basis) once a year at the time of Boro transplanting supplemented 50% of the fertilizer nutrients other than nitrogen (N) in the subsequent crop of the cropping pattern. A positive effect of GM on the yield of T. Aman rice was observed. Following GM, the application of reduced doses of phosphorus (P), potassium (K), sulfur (S), and zinc (Zn) to the second crop (T. Aman) did not reduce yield, indicating the beneficial residual effect of fertilizer applied to the first crop (Boro rice) of the cropping pattern. The comparable yield of T. Aman was also observed with reduced fertilizer dose in CD‐treated plots. The total P, K, and S uptake (kg/ha/yr) in the unfertilized plot under an irrigated rice system gradually decreased over the years. The partial nutrient balance in the unfertilized plot (T₁) was negative for all the nutrients. In the fertilized plots, there was an apparent positive balance of P, S, and Zn but a negative balance of N and K. This study showed that the addition of organic manure (CD, dhaincha) gave more positive balances. In the T_4c treatment at 0–15 cm, the application of chemical fertilizers along with the organic manures increased soil organic carbon by (C) 0.71%. The highest concentration of total N was observed with T_4c followed by T_4d and T_4b, where CD was applied in Boro season and dhaincha GM was incorporated in T. Aman season. The sixfold increase in soil‐available P in T_4b‐, T_4c‐, T_4a‐treated plots was due to the addition of CD. Dhaincha GM with the combination of chemical fertilizer helps to mobilize soil‐available P by 3 to 6 ppm. The highest amount of soil‐available S was found in T_4c‐ and T_4a‐treated plots. It was 2.5 times higher than that of the initial soil. The application of CD and dhaincha GM along with chemical fertilizers not only increased organic C, total N, available P, and available S but also increased exchangeable K, available Zn, available iron (Fe), and available manganese (Mn) in soil.     

Soil and Rice Responses to Phosphate Fertilizer in Two Contrasting Seasons on Acid Sulfate Soil

Acid sulfate soils (ASS) are characterized by low pH, aluminum (Al), and iron (Fe) toxicity and are typically deficient in phosphate (PO₄). The application of phosphorus (P) fertilizer could help reduce the level of exchangeable Al and Fe, thereby improving the rice growth and yield. Five levels of P (0, 20, 40, 60 and 80 kg phosphorus pentoxide (P₂O₅)/ha) were tested with rice varieties MTL560 in the wet season and MTL480 in the dry season. The optimum rate of P was 60 kg P₂O₅/ha for rice in the dry season and 80 kg P₂O₅/ha in the wet season. Soil testing showed at the start of the season that there was sufficient P in the soil. At the end of the season there was a reduction in soil Al and Fe in plots that had P rates above 40 kg P₂O₅/ha. It is therefore likely that P application reduced Al and Fe toxicity through precipitation and formation of Al-P and Fe-P compounds, which boasted yield, rather amending a soil P deficiency.     

Is UK biofuel supply from Miscanthus water‐limited?

Sustainable Miscanthus plantings encouraged under publicly funded schemes should be based on sound economic and environmental assessments. We developed an empirical yield model for Miscanthus from harvestable dry matter yields at 14 field trials in the UK to estimate site-specific and regional yields derived from meteorological variables and soil available water. Harvestable yields of crops established for at least 3 years at 14 arable sites across the UK ranged from 5 to 18 t/ha, averaging at 12.8 (±2.9) t/ha. Variables considered to affect yield were number of years after planting, length of season ( T _air > 9 °C), temperature, global solar radiation, precipitation and potential evapotranspiration during the season, and soil available water capacity ( AWC ). At a single site (Rothamsted), AWC and the relative average potential soil moisture deficit during the main growing season explained 70% of annual yield variation (RMSE = 1.38 t/ha, P  < 0.001). For the complete UK data set ( n  = 67), yield variation was related to AWC , air temperature and precipitation (RMSE = 2.1 t/ha, P  < 0.01). Linking soil survey and spatially interpolated weather data we calculated an overall national average dry matter yield of 9.6 t/ha. As shown for two counties (Oxfordshire and North Yorkshire), estimated yield may decrease by 1 t/ha, and its uncertainty may rise from 15 to >20%, when soil survey instead of local soil data are used. Using data from a single weather station can introduce a bias (<1 t/ha) because of differences in elevation and local temperature and precipitation. Overall, it seems most important for bioenergy plantings to assure sufficient water supply from the soil ( AWC  > 150 mm) during the main growing season.