The effect of catch crops on sulphate leaching and availability of S in the succeeding crop on sandy loam soil in Denmark

Sulphate leaching losses may reduce the long-term possibility of maintaining the S supply of crops in low input farming systems. The ability of catch crops (Italian ryegrass (Lolium multiflorum Lam), winter rape (Brassica napus L.) and fodder radish (Raphanus sativus L.)) to reduce soil sulphate concentrations in autumn and make it available to a succeeding crop was investigated in 1996–1998 on sandy loam soil in Denmark. All catch crops reduced soil sulphate concentrations in the autumn compared to bare soil. Especially, the cruciferous catch crops had the ability to deplete efficiently soil sulphate levels and thus, reduce the sulphate leaching potential. The S uptake in aboveground catch crop was 8, 22 and 36 kg S per ha for ryegrass, winter rape and fodder radish, respectively. In the following spring, sulphate levels of the autumn bare soil were low in the top 0.5 m and a peak of sulphate was found at 0.75–1 m depth. In contrast, where a fodder radish catch crop had been grown, high sulphate levels were present in the top 0.5 m, but only small amounts of sulphate were found at 0.5–1.5 m depth. In spring barley (Hordeum vulgare L.), that followed catch crops, S concentrations at heading and maturity revealed that the availability of soil S increased following winter rape and fodder radish, whereas there were indications that following ryegrass, the S availability was reduced compared to bare soil. This initial study showed that catch crops have a high potential for reducing sulphate leaching and may be used to synchronise S availability with plant demand in a crop rotation.     

Soil–plant nutrient balance of tea crops in the northern mountainous region,Vietnam

Unbalance of nutrients in soil–plant system is considered a cause of soil quality degradation in long-term tea cultivation in the northern mountainous region, Vietnam. The objective of this study was to measure the nutrient balance between plant removals, recycling, storage and addition in different tea age classes (10, 25 and 40 years old). Plant biomass and plant nutrient concentrations were measured for calculation of plant nutrient uptake. Nutrients accumulated in the plants and removed from harvest were considered as nutrient loss, while fertilizer was considered as nutrient inputs gain to soil. Plant nutrient concentrations such as N, P, K, S and Mg in the tea stands decreased in the order: young leaves (and buds) > mature leaves > branches > stems. Age of the tea plantations had no significant effect on tissue concentrations of N, Ca, or Mg. However, there were significant differences between tea age classes for K (in both the young and mature leaves) and for P and S (in the mature leaves). The results from the study also showed that fertilizer inputs meet the crop nutrient demands (nutrient loss from harvest). However, if some other nutrient pools (e.g. nutrient leaching, storage in the plants) are accounted for the total nutrient budget, these inputs of fertilizer may not be enough to balance total nutrient losses.     

Does Tephrosia candida as fallow species, hedgerow or mulch improve nutrient cycling and prevent nutrient losses by erosion on slopes in northern Viet Nam?

Agroforestry is considered to be a promising alternative to short-fallow shifting cultivation or other monocropping systems. An on-farm experiment was established in 1996 in northern Viet Nam to examine the contribution of the leguminous bush Tephrosia candida (Roxb.) D.C. as a fallow or hedgerow species and as a mulch producer to improve nutrient cycling and prevent nutrient losses by erosion. The systems tested were upland rice monocropping (Mono), natural fallow (NaFa), fallow of Tephrosia (TepFa), hedgerow intercropping with upland rice (Oryza sativa L.) and internal mulching using pruned Tephrosia biomass (TepAl), and upland rice with external mulching using Tephrosia biomass (TepMu). Over two cropping seasons, from April 1996 to April 1998, nutrients recycled and inputs and exports were recorded, as well as changes in C-, N- and P-pools, and in pH in the 0–5 cm topsoil layer.The Tephrosia systems (TepFa, TepAl, TepMu) prevented nutrient losses by erosion effectively. Compared to the NaFa system, the TepFa system accumulated 34% more N in the above-ground plant parts and increased topsoil N by 20%, probably due to N-fixation. There was a trend that the less labile P-pools (NaOH-P) were reallocated into the more labile P-pools (Bicarb-P) in the soil of the TepFa system. Burning released significant amounts of the inorganic P-pools in both the NaFa and TepFa systems and this effect seemed to be more pronounced in the TepFa than in the NaFa. Organic input to crop export ratios for N and P were >1 in the TepAl and TepMu treatments. This was due to a sufficient quantity and quality of the Tephrosia mulching material. However, moderately labile NaOH-extractable organic P seemed to be depleted in the topsoil due to high P uptake in the TepMu treatment. Thus, nutrient cycling and nutrient balances were improved under the Tephrosia systems. But for long-term P sustainability, there is a belief that a combined use of mulching and mineral P fertiliser is needed.     

外源氮输入对生长季黄河口碱蓬-土壤系统磷分布规律的影响

为研究氮负荷不断增强情况下黄河口湿地磷的生物循环状况,选择黄河入海口北部滨岸高潮滩的碱蓬湿地为研究对象,基于野外原位氮（N）输入模拟试验,研究不同氮输入梯度[N0（对照处理）,6.0 g/（m2·a）;N1（低氮处理）,9.0 g/（m2·a）;N2（中氮处理）,12.0 g/（m2·a）;N3（高氮处理）,18.0 g/（m2·a）]下生长季碱蓬湿地植物-土壤系统中w（TP）分布特征的差异.结果表明:外源氮输入对湿地表层（0~10 cm）土壤中w（TP）变化的影响较为明显,N2和N3处理下w（TP）整体高于N0和N1处理.不同氮处理下植物各器官的w（TP）生长初期表现为根>叶>茎,生长旺期和末期表现为叶>根>茎,说明叶是磷的主要累积器官.外源氮输入改变了碱蓬湿地的养分限制状况,随着氮输入量的增加,土壤和植物-土壤系统磷储量、氮供给的增幅远低于植物亚系统,说明氮、磷之间的养分供给存在不同步性.研究显示,在未来黄河口氮养分负荷不断增加的情况下,碱蓬湿地植物-土壤系统极有可能通过加速磷的生物循环来缓解日益加剧的磷养分限制状况,进而使得氮、磷养分之间可能形成正反馈机制,而这将有利于维持湿地系统的稳定与健康.      

黄河三角洲湿地不同植被类型下土壤营养元素空间分布及其生态化学计量学特征

选取黄河三角洲芦苇湿地、柽柳湿地、盐地碱蓬湿地和光滩这4种典型自然湿地及农垦地棉花田作为研究对象,阐明不同植被类型自然湿地土壤营养元素分布特征和生态化学计量学特征,并进行农垦地同自然湿地的对比研究.结果表明,自然湿地内土壤总有机碳（TOC）和总氮（TN）含量总体表现为：芦苇湿地、柽柳湿地>盐地碱蓬湿地>光滩,TOC和TN含量同土壤电导率值（EC）和pH值呈显著负相关（P<0.05）;棉花田TOC、 TN和全磷（TP）含量显著高于自然湿地（P<0.05）,其中硝态氮（NO^-₃-N）含量为自然湿地的9.4～11.4倍,但棉花田碳、氮和磷含量同EC值和pH值无显著相关性（P>0.05）.相关分析表明,自然湿地土壤碳氮比（C/N）主要受控于TN含量（P<0.05）,棉花田土壤C/N显著低于自然湿地（P<0.05）.自然湿地及棉花田土壤碳磷比（C/P）和氮磷比（N/P）均值较低,且与土壤TOC和TN含量变化趋势一致.对比分析发现,整体上棉花田土壤营养元素含量、 C/N、 C/P和N/P差异显著（P<0.0...     

Nitrate leaching from a free-draining volcanic soil irrigated with municipal sewage effluent in New Zealand

Land application of municipal sewage effluent is becoming increasingly popular worldwide as a means of disposal, treatment, nutrient recycling, irrigation to meet plants' water requirements, and groundwater recharge. Nitrate leaching from a volcanic soil (Typic Udivitrand) was investigated under a Pinus radiata plantation near Rotorua, New Zealand, which had received, on average, 0, 29, and 88 mm per week of tertiary-treated municipal sewage effluent for the previous 4 years. Four replicates of undisturbed soil monolith lysimeters (200 mm diameter×200 mm depth) from surface soil from each treatment were used to study the influence of the three different rates of effluent application on N leaching. A rapid emergence of nitrate–N occurred in the drainage samples, and indicated that approximately up to half of soil nitrate was readily leached beyond the topsoil. Nitrate–N concentrations in the drainage water increased substantially with effluent application rate, almost reaching the World Health Organisation recommended limits (approximately 10 g m⁻³) in plots receiving effluent at the highest rate. Given that nitrate leaching from the soils may threaten the viability of the land treatment system, due to large N loads being observed in streams which drain irrigated catchments during winter periods, possible strategies for minimising nitrate leaching losses under effluent irrigation may need to be considered.     

Nutrient recycling during the decomposition of apple leaves (Malus domestica) and mowed grasses in an orchard

Each year, significant fractions of nutrients absorbed by trees and orchard grasses, return to the soil by abscised leaves and mowed biomass. Using litter bag technique and labelled (¹⁵N) litter, we assessed the decay dynamics and the related nutrient releases in a mature, drip irrigated, apple (Malus domestica) orchard located in the Eastern Po Valley (Italy) on a silty clay loam soil. Litter bags containing abscised apple leaves were placed in December 2001 on the soil surface and collected over a 2-year period, while the decomposition of perennial ryegrass was studied over a 6-month period from May 2002. The dynamics of mass and C losses from decomposing apple leaves fitted to a single exponential decay model. At 1 year from their placement, about 50% of original mass was lost, while and additional 20% was not recovered in the second year. Initial C losses were not accompanied by degradation of cellulose which started only in the spring of the year after their placement on the soil. Along with the decomposition process, the remaining litter was progressively enriched in lignin-like compounds. Net N and S immobilization occurred during the winter–spring period and net release of these nutrients occurred only in the second year. Ryegrass lost about half their mass and original N content after 6 weeks and most of sward derived N was recovered in the underneath soil volume. Both apple and ryegrass released most their initial K content during the period of decomposition. The knowledge of the dynamics of nutrient release on the orchard floor will be useful for predicting nutrient availability for tree uptake and therefore for managing amounts and dynamics of nutrient supply.     

有机肥施用对田面水氮磷流失风险的影响

为探明化肥配施有机肥对田面水氮、磷流失及水稻系统养分吸收的影响,采用田间小区试验,设置常规施肥处理（FN）、常规施肥减氮磷量20%处理（F0）、减氮磷20%+有机肥处理（F1~F4处理有机肥施用量分别为1 500、3 000、4 500和6 000 kg/hm2）共6个处理,探索化肥减量20%配施有机肥的最优组合.结果表明:不同施肥处理下,田面水中ρ（TN）、ρ（NH₄+-N）均于施肥后第1天达到峰值,随后迅速下降,于第7天后逐渐趋于稳定,ρ（TN）和ρ（NH₄+-N）分别维持在各自峰值的5.1%~10.9%与4.8%~9.6%,田面水中ρ（TP）的变化趋势与ρ（TN）相似;F0与F1处理均能有效降低田面水中ρ（TN）和ρ（TP）.与FN处理相比,F1处理下ρ（TN）、ρ（NH₄+-N）与ρ（TP）平均值分别降低了6.5%、9.1%和3.1%,该处理能够有效地降低氮、磷养分流失风险,且增施有机肥可使水稻增产0.2%~19.8%,地上部分氮、磷累积量随有机肥施用量的增加而显著增加（P < 0.05）.综合水稻产量、养分吸收和田面水养分动态等指标发现,F1处理不仅能提高区域双季稻产量,还能有效控制田面水氮、磷养分浓度,降低氮、磷地表径流产生的农田面源污染风险,是针对南方双季稻田的一项"控源节流"优化施肥模式.      

Influences of nitrification inhibitor 3,4-dimethyl pyrazole phosphate on nitrogen and soil salt-ion leaching

An undisturbed heavy clay soil column experiment was conducted to examine the influence of the new nitrification inhibitor, 3,4- dimethylpyrazole phosphate （DMPP）, on nitrogen and soil salt-ion leaching. Regular urea was selected as the nitrogen source in the soil. The results showed that the cumulative leaching losses of soil nitrate-N under the treatment of urea with DMPP were from 57.5% to 63.3% lower than those of the treatment of urea without DMPP. The use of nitrification inhibitors as nitrate leaching retardants may be a proposal in regulations to prevent groundwater contaminant. However, there were no great difference between urea and urea with DMPP treatments on ammonium-N leaching. Moreover, the soil salt-ion leaching losses of Ca^2＋, Mg^2＋, K^＋, and Na^＋ were reduced from 26.6% to 28.8%, 21.3% to 27.8%, 33.3% to 35.5%, and 21.7% to 32.1%, respectively. So, the leaching losses of soil salt-ion were declined for nitrification inhibitor DMPP addition, being beneficial to shallow groundwater protection and growth of crop. These results indicated the possibility of ammonium or ammonium producing compounds using nitrification inhibitor DMPP to control the nitrate and nutrient cation leaching losses, minimizing the risk of nitrate pollution in shallow groundwater.     

蚯蚓、秸秆和柠檬酸对少花龙葵与翅果菊修复锌铅镉污染土壤的影响

外源物质调控和间作是提高重金属污染土壤植物修复效率的有效方法.采用盆栽试验研究蚯蚓、秸秆和柠檬酸对少花龙葵和翅果菊单作与间作修复Zn、 Pb和Cd复合污染土壤的影响.结果表明,蚯蚓对Zn、 Pb和Cd的富集系数(BCF)分别为0.07～0.13、0.10～0.26和5.64～15.52.土壤中添加秸秆能使蚯蚓生物量增加22.29%～223.87%、重金属含量下降8.15%～62.58%.蚯蚓对土壤重金属有效态含量的影响不大,但秸秆和柠檬酸对土壤重金属有效态含量分别表现为钝化和活化作用.蚯蚓对翅果菊的重金属含量影响不大,但会降低少花龙葵的重金属含量;秸秆对翅果菊重金属含量表现为抑制效应,但对少花龙葵Cd含量表现为促进效应;柠檬酸对少花龙葵重金属含量影响不大,但是会显著提高翅果菊的Pb含量.间作显著降低土壤重金属有效态含量,明显提高植物根的重金属含量,但对植物地上部重金属含量影响不大.植物对Zn、 Pb和Cd的总提取量主要表现为：翅果菊>间作>少花龙葵.添加蚯蚓可以使翅果菊Zn、 Pb和Cd总提取量分别提高12.49%、35.89%和29.01%;添加秸秆+蚯蚓可以使翅果菊Pb...     

土壤中氯苯类化合物的迁移行为

为了污染土壤的恢复 ,应用土壤污染实时模拟系统 ,研究土壤中氯苯类化合物的迁移行为 .结果表明 ,氯苯类化合物主要滞留在土壤相中 ,在气、液 2相中的含量随着其蒸汽压和水溶性的增大而增大 ;15cm以上土壤中的氯苯类化合物由最初的均匀分布 ,变为从上至下浓度逐渐增大的分布 .渗滤液中的氯苯类化合物随渗滤水量变化为 2个阶段 ,渗滤水量 <1000 ml时 ,浓度随水量逐渐下降 ;而渗滤水量 >1000 ml后 ,浓度变化不大 ,趋于某一稳定的浓度值 .氯苯类化合物在土壤层和渗滤水中浓度的变化可较好地用吸附模型来解释 .不同氯苯类化合物的挥发速率随时间延长而降低 ,挥发速率与氯苯施加量的对数和蒸汽压呈良好线性关系 .     

Differential N uptake by maize cultivars and soil nitrate dynamics under N fertilization in West Africa

Nitrate is prone to leaching in the sandy soils of the West African moist savannas. Better management of nitrogen (N) resources and maize cultivars with enhanced genetic capacity to capture and utilize soil and fertilizer N are strategies that could improve N-use efficiency. In two field experiments conducted at Zaria, northern Nigeria, five maize (Zea mays L.) cultivars planted early in the season were assessed under various N levels for differences in N uptake, soil N dynamics, and related N losses. Cultivar TZB-SR accumulated more N in the aboveground plant parts in both years than the other cultivars. All, except the semi-prolific late (SPL) variety, met about 50–60% of their N demand by the time of silking (64–69 DAP). In both years, SPL had the greatest capacity to take up N during the grain filling period, and it had the highest grain-N concentration and the least apparent N loss through leaching in the second year. There were no significant differences in soil N dynamics among cultivars in both years. At harvest, the residual N in the upper 90 cm of the profile under all the cultivars ranged from 56 to 72 kg ha⁻¹ in the first year and from 73 to 83 kg ha⁻¹ in the second year. Apparent N loss from 0 to 90 cm soil profile through leaching ranged from 35 to 122 kg ha⁻¹ in both years. N application significantly increased N uptake by more than 30% at all sampling dates in the second year of the experiment, but had no effect on apparent N loss. Results indicate that the use of maize cultivars with high N uptake capacity during the grain filling period when maximum leaching losses occur could enhance N recovery and may be effective in reducing leaching losses of mineral N in the moist savanna soils.     

基于机器学习的长江流域农田氮径流流失负荷估算

定量解析长江流域农田氮径流流失特征是实现长江及其河口氮污染有效控制的关键科学基础.基于收集的长江流域570个旱地和434个水田田间氮径流流失数据组,采用相关性分析、结构方程模型、方差分解和机器学习方法,探究了影响旱地和水田总氮径流流失强度的主要因素,建立了基于机器学习的长江流域旱地和水田总氮径流流失强度预测模型,量化了长江流域农田总氮径流流失负荷.结果表明,径流深、施氮量和土壤氮含量是影响旱地总氮径流流失强度的主要因素;径流深和施氮量是水田总氮径流流失强度的主要影响因素.与分类与回归树、多元线性回归和增强回归树方法相比,采用随机森林算法构建的长江流域旱地和水田总氮径流流失强度预测模型具有更高的精度（R²为0.65~0.94）.基于随机森林算法的预测模型估算的2013年长江流域农田总氮径流流失负荷（以N计）为0.47 Tg ·a^-1（旱地：0.25 Tg ·a^-1;水田：0.22 Tg ·a^-1）,中下游地区贡献了58%的流失负荷.模型预测5种防治情景下的长江流域农田氮流失负荷可削减2.4%~9.3%,其中减少径流量的削减效果最为显著.长江流域农田氮面源污染防治必须协同加强氮肥精准管理、减少农田径流量和提高土壤氮利用,且应将重点放在中下游地区.所发展的基于机器学习建模方法克服了氮径流流失强度与影响因素之间函数关系难以确定的问题,为估算区域或流域农田氮流失负荷提供了简便且可靠的方法.     

秸秆还田配施化肥对土壤养分及冬小麦产量的影响

为探究关中地区秸秆还田配施化肥对土壤养分和冬小麦产量的影响,研究采用裂区试验设计,主区为：秸秆不还田（S₀）和秸秆还田（S）;副区为：不施肥（WF）、氮肥（NF）和氮磷肥（NPF）.应用生态化学计量的方法,探究秸秆还田配施化肥下土壤碳氮磷含量变化及其和产量的关系.结果表明,秸秆和施肥互作对表层（0~20 cm）土壤有机碳、全氮和全磷含量均产生显著影响（P<0.05）.与S₀WF处理相比,SNPF处理显著提高表层（0~20 cm）土壤有机碳和全氮含量（P<0.05）.秸秆和年份互作对表层（0~20 cm）土壤全氮含量产生显著影响（P<0.05）,随着秸秆还田时间的增加,在2021年SWF处理下表层（0~20 cm）土壤全氮含量显著高于S₀WF （P<0.05）.秸秆和施肥及其互作对20~40 cm土层有机碳和全氮含量无显著影响（P>0.05）,但对20~40 cm土壤全磷含量产生显著影响（P<0.05）,与SWF处理相比,SNPF处理显著增加了20~40 cm土层全磷含量（P<0.05）.秸秆还田配施化肥对土壤化学计量特征也产生显著影响.与S₀WF处理相比,S₀NPF处理能够降低表层（0~20 cm）土壤C：N,提高表层（0~20 cm）土壤C：P和N：P.与SWF处理相比,SNF处理能够降低表层（0~20 cm）土壤C：N.秸秆还田配施化肥对冬小麦产量也产生显著影响,2020年和2021年SNPF处理与S₀WF处理相比分别增产24.23%和28.9%.相关性分析表明,产量与C：N （P<0.05）和C：P （P<0.01）呈显著正相关关系.全氮和N：P与处理年份呈极显著正相关关系（P<0.001）.综上所述,在关中地区秸秆还田配施氮磷肥处理（SNPF）会改善土壤养分,改变土壤化学计量特征,同时提高产量.因此,本研究结果表明秸秆还田配施氮磷肥（SNPF）是优化区域农田养分管理,提高粮食生产能力的有效途径.     

安徽庐江潜在富硒土壤硒生物有效性及其影响因素

为研究潜在富硒土壤硒生物有效性,采集安徽庐江潜在富硒地区64组水稻及对应根系土壤样品,分析土壤理化性质、土壤养分、全硒、不同形态硒及大米硒含量,采用线性回归法探究土壤硒生物有效性的影响因素.结果表明,大米硒含量（记作Se_rice,下同）为0.037~0.120 mg/kg,土壤全硒含量（记作Se_tot,下同）为0.260~1.177 mg/kg,土壤硒以腐殖酸态硒（15.5%~44.7%）、强有机态硒（12.5%~53.3%）和残渣态硒（8.1%~68.5%）为主.土壤有效硫、有效磷通过提高强有机态、腐殖酸态和浸提性硒含量并促进水稻籽实（大米）对硒的吸收,而土壤阳离子交换量（cation exchange capacity,CEC）、速效钾、全铁和全锰通过降低水稻生物可利用态硒含量（包括水溶态、腐殖酸态、强有机态和浸提性硒）抑制水稻籽实（大米）对硒的吸收.Se_tot与Se_rice显著正相关（R=0.616,P < 0.01）,非残渣态硒含量与有机质含量之比（记作NRE-Se/OM）与Se_rice相关性最强（R=0.774,P < 0.01）.土壤NRE-Se/OM、有效硫、有效铁、全锰构建的多元逐步线性对数回归模型可解释水稻籽实（大米）吸收硒的76.0%的方差.因此引入变量NRE-Se/OM,并结合土壤有效硫、有效铁和全锰能有效评价和预测研究区土壤硒生物有效性.      

Effects of a winter legume on phosphorus,potassium, calcium and magnesium cycling in a humid subtropical agroecosystem

Phosphorus, potassium, calcium and magnesium cycling were compared in sorghum agroecosystems with winter legume (Trifolium incarnatum L.) or inorganic fertilizer nitrogen inputs. The system with fertilizer N input had winter rye (Secale cereale L.) as a winter cover crop. Nutrient uptake by winter and summer crops, double acid extractable soil nutrients, soil pH and soil ammonium/nitrate ratio were measured. The legume took up more of all nutrients than the rye and also provided higher amounts of available nutrients in soil for the subsequent summer crop. Soil pH was also increased in the clover-N treatment. Nutrient uptake by winter crops is important for reducing leaching losses and chemical fixation of nutrients in humid subtropical regions.     

低分子量有机酸提取土壤中部分重金属的拟合模型研究

为研究不同浓度低分子量有机酸与提取的土壤重金属含量之间的关系,本文以采自安徽省安庆市某铜矿区及其周围的土壤为例,通过浸提法,研究了不同浓度苹果酸、甲酸对采样点土壤中重金属Cu、Mn、Zn、Pb提取能力的影响并进行模型拟合.结果表明:不同浓度苹果酸和甲酸对采样点土壤中重金属的提取量不同,两种有机酸对低pH、高重金属含量采样点及其周围土壤中的重金属提取量较大,两种低分子量有机酸对S6采样点的重金属Mn的提取量最大,分别为322.5 mg·kg~(-1)和193.58 mg·kg~(-1),提取率达70.02%和42.03%,Zn、Pb次之,Cu最低;随着苹果酸、甲酸浓度的升高,土壤中重金属Cu、Mn、Zn、Pb的提取量增加,苹果酸对土壤中重金属的提取能力大于甲酸;拟合模型对于两种低分子量有机酸与其提取的土壤中部分重金属含量之间的关系,具有较好的拟合性,其决定系数R~2在0.8293～0.9990之间,都具有显著性(p0.05),该模型可以定量表征低分子量有机酸对土壤重金属的提取能力,此研究结果为土壤中重金属的固定化和增强植物修复受重金属污染的土壤提供了理论支持.     

Control division of agricultural non-point source pollution at medium-sized watershed scale in Southeast China

This paper presents the study carried out for controlling agricultural non-point source pollution (NSP) in a medium-sized watershed covering 1.47 × 10⁴ km² in Southeast China using quantitative analysis coupled with geographic information system (GIS), universal soil loss equation (USLE), soil conservation service-curve number (SCS-CN), nutrient loss equations, and annualized agricultural nonpoint source model (AnnAGNPS). Based on the quantitative results derived from GIS and environmental models, five control division units were generated for NSP control in Jiulong River watershed, namely, controlling unit for soil losses, controlling unit for livestock breeding and soil losses, controlling unit for excessive fertilizer use and livestock breeding, controlling unit for soil losses and fertilizer use, and controlling unit for excessive fertilizer use and soil losses. This study proved that integrating GIS with environmental models can be adopted to efficiently evaluate major sources and contributors of NSP, and identify the critical source areas of NSP, which enables adjusting measures to local conditions by further control division units developed through such study for control and management of water quality degradation induced by NSP in the Jiulong River watershed. __________ Translated from Research of Environmental Sciences, 2006, 19(4): 119–124 [译自: 环境科学研究]     

生物炭配施磷肥对土壤养分、酶活性及紫花苜蓿养分吸收的影响

生物炭作为一种既能单独施用,又能与化肥共同施用的土壤改良剂,在农业生产实践中被广泛施用.然而,关于不同粒径生物炭与磷肥联合施用对土壤和植物的影响研究较少.采用盆栽试验,研究在两个磷水平下,不同粒径生物炭对土壤养分、酶活性以及紫花苜蓿养分吸收的影响[生物炭根据直径分为：C1(>1 mm)和C2(<0.01 mm)这两种处理].结果表明,生物炭和磷联合施用显著提高了土壤养分、酶活性和苜蓿养分吸收;其中,C2处理显著提高了土壤有效磷含量(P<0.05)和磷酸酶活性(P<0.01),而C1处理对铵态氮、硝态氮、脲酶和过氧化氢酶活性有显著影响(P<0.05).并且,不同粒径生物炭处理间的养分及酶的差异受到土壤磷水平的影响,P0水平下,C1和C2处理的铵态氮和硝态氮含量并没有显著差异;而在P1水平下,C1处理的铵态氮和硝态氮含量比C2处理高24.19%和18.68%(P<0.05),但C1和C2处理的有效磷之间并无显著差异;磷添加显著提高了苜蓿地上和地下部的N和P含量(P<0.05),但是不同粒径生物炭之间苜蓿养分含量并没有显著影响.综上所述,生物炭与磷肥...     

Winter losses of nitrogen and phosphorus from Italian ryegrass, meadow fescue and white clover in a northern temperate climate

We have studied to what degree Italian ryegrass (Lolium multiflorum Lam.), white clover (Trifolium repens L.) and meadow fescue (Festuca pratensis L.) are able to preserve nitrogen (N) and phosphorous (P) in shoots and roots from one growing season to the next in a northern temperate climate. Field experiments were performed during four consecutive winters in central southeast Norway (60°42′N, 10°51′E), and N and P in plant biomass were measured in the autumn and in the spring. We also measured the contents of total N, total P and organic carbon (C) in seepage water that percolated through the aboveground plant material. Uptake of N and P in Italian ryegrass and white clover was substantially larger than in meadow fescue. The winter losses varied greatly from year to year, depending on the winter climate. On the average for all three of the plant species, the winter losses of N from aboveground biomass were 6, 35, 68 and 10% in the four experimental years, respectively. The corresponding P losses were 11, 36, 60 and 22%. On the average for all plant species and experimental years, 43 (±12)% (S.E., n = 12) of the N, 34 (±9)% of the P and 4 (±1)% of the C that was lost from the aboveground plant biomass during the winter, was recovered in seepage water, basically as a nutrient pulse in melt water in early spring. The very low C recovery rate in seepage water suggested a considerable microbial growth on lost plant C. Assuming that all un-recovered plant C was consumed by microorganisms not included in measurements of the seepage water, modelling showed that microbial immobilisation theoretically might explain the unexpectedly low recovery rates of N and P. The study was not designed to investigate the possible effects of psychrophilic microbes on N and P cycling. Therefore, it is inconclusive and underlines the need for more knowledge on this matter.