低分子量有机酸对土壤磷释放动力学的影响

模拟植物在缺磷条件下,根系所分泌的有机酸种类和数量,用流动法研究了柠檬酸,苹果酸,草酸和酒石酸对土壤磷释放的影响。结果表明：有机酸能明显促进土壤中磷的释放,不同有机酸对石灰性土壤活化能力大小的次序为草酸≥柠檬酸〉苹果酸〉酒石酸;而对酸性土壤磷的释放量与Ｆｅ＋Ａｌ释放量之间呈极 相关,有机酸活化土壤磷能力大小的次序为柠檬酸〉草酸〉酒石酸〉苹果酸。     

土壤磷长期解吸研究的新方法

介绍一种研究磷素解吸动力学的新方法。这种新方法利用装填水合三氧化二铁（作为无限吸附Ｐ源）的透析膜管。由于加入了微生物抑制剂（例如四氯化碳）以阻止膜的水解，该系统在很长的反应期内也相当稳定。在解吸期间，土壤溶液的ｐＨ值基本保持恒定。土壤悬液和磷源作用一段时间后，磷源可很容易地从土壤悬液中分离出来而土壤材料不损失。因而，该方法与氧化铁浸润滤纸磷提取法相比有很大的优点。该方法能保持溶液中恒定的低磷活性，     

土壤磷的化学行为与有效磷的测试

本文对土壤磷的化学行为在理论上作了较系统的论述,包括土壤中不同形态和不同状态的磷化合物的组成、含量、性质及其在土壤中的转化等。并据此对现行主要的土壤有效磷的测试机理作了一定的剖析。     

黄土旱塬施肥对土壤颗粒组成及其有效磷富集的影响研究

通过田间试验与室内分析相结合的方法研究长期不同施肥处理下土壤颗粒组成及其有效磷富集。结果表明,各施肥处理土壤颗粒组成都呈现颗粒愈小比例愈高的规律,而不同施肥处理对同一粒径颗粒含量又有一定的影响。在单施磷肥(P)的基础上,配施氮肥、有机肥(NP、PM、NPM)有利于增加<0.25mm颗粒的比例,以NPM处理最为明显。长期施用有机肥改善了土壤颗粒中有效磷水平,但也提高了土壤颗粒有效磷中水溶性磷的比例。土壤中的有效磷(包括速效磷、水溶性磷)主要富集在<2mm粒径的土壤颗粒中,<0.25mm的土壤颗粒中有效磷富集率最高。氮磷配施(NP)、氮磷有机肥配施(NPM)有利于增加<0.25mm颗粒中土壤有效磷的富集,PM处理更促进土壤有效磷在0.25～2mm粒径中富集。     

几种土壤的磷吸持动力学及其影响因素的研究

本文研究了江苏、江西５种性质变化较大的土壤样品，在不同磷酸根溶液浓度，不同支持电解质浓度，振荡及磁搅拌两种实验条件下土壤磷吸持动力学特性。     

连续施肥对土壤磷钾组分变化的影响

以 10年肥料定位试验土壤为材料 ,研究了连续施肥对 3种土壤磷钾组分含量的影响。结果表明 ,连续施用NPK化肥、化肥基础上增施有机肥 ,均可提高土壤有机磷总量、无机磷总量、全钾含量及其它各组分 (形态 )的含量。有机磷总量平均分别提高 0.34倍和 1.08倍 ,其中AOP提高 1.71倍和 2.45倍 ;无机磷总量分别提高 0.40倍和 0.47倍 ,其中Ca2-P提高 6.3倍和 7.69倍 ;全钾含量提高很少 ,但水溶性钾提高 6.88倍和 11.17倍。连续 10年不施肥土壤磷钾总量及各组分含量均降低。连续施钾与不施钾 ,土壤粘粒X射线衍射图谱没有明显差异 ,但不施K肥土壤粘粒 ( 2 m)全钾含量降低     

磷处理土壤中磷的释放动力学研究

Phosphate release from three selected soils after treatments of 1.6 and 2.4 mmol L^-1 P was investigated using sequential extractions and fitted using six kinetic models, including zero order （Z）, first order （F）, second order （S）,parabolic diffusion （PD）, two constant rate （TC）, and Elovich type （ET） equations. The results showed that the rate of P release was initially rapid and then gradually declined with time. Also, P release increased with added P. Total P release followed the order： paddy soil with 2.4 mmol L^-1 P 〉 red soil with 2.4 mmol L^-1 P 〉 paddy soil with 1.6 mmol L^-1 P〉 fluvo-aquic soil with 2.4 mmol L^-1 P 〉 fluvo-aquic with 1.6 mmol L^-1 P 〉 red soil with 1.6 mmol L^-1 P. For the two P treatments P release from the paddy soils in the first extraction was 44.3% and 45.6% of total released P, respectively,which were higher than those from red and fluvo-aquic soils. The ratio of P release at the end of release time was 14.0%and 13.1% in the paddy soil treated with 1.6 and 2.4 mmol L^-1 P, respectively, but only 5.1% and 9.2% in the red soil and 7.0% and 5.2% in the fluvo-aquic soil, respectively. Comparison of the coefficients of determination （R^2） indicated that ET, TC, and PD equations could describe the P release data better than Z, F, and S equations.     

施用石灰对土壤吸附磷的影响

本文测定了14种酸性土壤的磷吸附等温线,利用土壤磷吸附特征参数与土壤理化性质的关系,研宄了施用石灰对土壤吸附磷的影响及其机理。     

低分子量有机酸对石灰性土壤磷吸附动力学的影响

根据植物在缺磷胁迫下,根系分泌的有机酸种类的数量,用流动法研究了柠檬酸、苹果酸、草酸和酒石酸对石灰性土壤磷吸附动力学的影响。结果表明：有机酸均能明显降低土壤对磷的吸附,不同有机酸降低磷吸附的能力大小的次序为草酸≥柠檬酸〉苹果酸≥酒石酸。     

亚洲热带地区的土壤资源及土地利用

Tropical Asia is a region comprising South and Southeast Asia and under strong influence of the Asian monsoon climate.It is characterized by and extremely high population density and by high land use intensity.Paddy rice cultivation is the most important form of agriculture in the greater aprt of the region.Soil resources of tropical Asia have a specific feature in comparison with tropical Africa and America.Ultisols dominate in uplands,and lowland soils like Inceptisols and Histosols are relatively abundant.The latter point is made clearer if we take the landforms of the region with a vast extent of lowlands into consideration.Geologically,tropical Asia with the Himalayan orogeny and active volcanism exhibits a conspicuous contrast to tropical Africa and America with the dominance of the shield structure.This along with the monsoon climate should have determined the basic features of landforms and soil,and acoordingly all the agricultural and social characteristics of tropical Asia today,Although paddy rice cultivation in the lowland is highly sustainable,upland cultivation in extensive Ultisol areas tends to be handicapped by low fertility and high erodibility of the soil,resulting in low sustainability.Land shortage is compelling people to exploit slopelands in hills and mountains,on the one hand,and thus far unutilized coastal lowlands,on the other,Both of these new reclamations are facing to serious land degradation problems todary.Torpical Asia will continue to be the most densely populated region of the wolrd with ever-increasing population.In order to meet the increasing food demand lowlang rice cultivation should beintensified by the infrastructure development to ease the stresses on slopelands and vulnerable coastal lowlands.At the same time,upland crop production in Ultisol areas should be stabilized and enhanced,providing integrated nutrient management and measures for soil conservation.     

中国亚热带地区土地利用和磷释放的数量关系

The increase of phosphorus concentration is a crucial factor causing the eutrophication of water body.while land use has an important impact on agricultural non-point sources(NPS) phosphorus discharge,Seven sites controlling the water in four sub-watersheds and the main exit of the Meicun Watershed of Xuancheng County,Anhui Provinec,were investigated by dynamic monitoring of stream water and nutrient discharge,integrating interpretation of areial image and GIS analysis to find out how the land use affects phosphorus loss with stream water in typical agriculture-forest watershed in subtropica China.These monitored sites are different in structure of typical agriculture-forest watershed in subtropical China.These monitored sitess are different in structure of land use,Phosphorus concentration of the stream water was analyzed every week and at the next day of rainfall,The velocity of flow was measured by kinemometer to calculate the runoff flux and phosphorus discharge.The results showed that the runoff flux and the discharges of dissolved phosphorus(DP),particle-associated phosphorus(PAP) and total phosphorus(TP) had significant exponential relationships with the area percentages of forest,pond and paddy field.There existed a significant exponential relationships with the area percentages of forest,pond and paddy field.There existed a significant linear relationship between the TP and PAP concentrations in stream water and the area percentages of forest,pond and paddy field,and the discharge of PAP was also significantly linearly correlated with the discharge of suspended soil particles.There was a logarithmic linear relationship between DP and PAP discharges,The study indicated that the adjustment of land used patterns and construction of ecologically sound aldnscape would be an important measure to reduce the runoff discharge of phosphorus,The results would be very useful in building the best management practices(BMPs) of agricultural watershed in subtropics.     

Soil nutrient changes due to land use changes in Northern China: a case study in Zunhua County, Hebei Province

Abstract. Since the 1980s, land use in rural areas of China has changed greatly as the result of political initiatives. These changes have caused soil nutrient changes which are examined in this paper for Zunhua County, northern China from 1980 to 1999. The areas of farmland, grassland, and paddy decreased greatly and were replaced by increases in forest and residential land. The soils under forest in 1999 transformed from farmland in 1980 increased in organic matter by 21%, total nitrogen by 18%, available nitrogen by 65%, available phosphorus by 17% and available potassium by 17%. Similarly, in the area which was converted from farmland in 1980 to grassland in 1999, soil organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium increased by 38%, 37%, 71%, 2% and 28%, respectively. Changes from farmland to forest and grassland not only changed land cover but also improved soil fertility and probably reduced soil nutrient losses.     

Chemical fractionation of phosphorus in calcareous soils of Hamedan,western Iran under different land use

We investigated the effects of land uses on P distribution and availability in selected calcareous soils under different management practices. KCl‐P (labile P), NaOH‐P (Fe‐Al‐bound P), HCl‐P (Ca‐bound P), and residual P (Res‐P) fractions at 0–30 cm depth were determined for soils planted to garlic, orchard, pasture, potato, leafy vegetables, and wheat. Trends in P distribution between chemical fractions were similar between land uses. Ca‐bound P was the most abundant P fraction in the soils, constituting between 61% and 78% of the total P, whereas P associated with labile was less abundant (< 2%). Soils under leafy vegetables and wheat along with pasture presented the highest and lowest values in all fractions of P, respectively. Labile P generally was highest for leafy vegetables and potato. Labile P and Fe‐Al‐bound P comprised < 1.4% and 8% of total P, respectively. Residual P ranged from ≈ 14% (potato and garlic) to 31% (pasture). Long‐term fertilization increased P allocation to inorganic fractions, as Ca‐bound P contained 78% of total P for potato and garlic and 74% for leafy vegetables but 61% for pasture. A strong positive correlation between labile P and Fe‐Al‐bound P (r = 0.534, p < 0.01), labile P and Ca‐bound P (r = 0.574, p < 0.01), Ca‐bound P and Fe‐Al‐bound P (r = 0.504, p < 0.01), Olsen‐P and CaCl₂‐P (r = 0.821, p < 0.01) was found. Principal‐component analysis showed that the first four components accounted for most of the variation, 32.5%, 16.9%, 12.9%, and 7.9% of total variation, respectively.     

Carbon,nitrogen, phosphorus and enzymatic activity under different land uses in a tropical,dry ecosystem

We compared total C, N and P, available forms of N and P and dehydrogenase, urease and acid phosphatase activities in soils from primary forests, 26‐year‐old pastures and 26‐year‐old secondary forests in the tropical dry forest region of Chamela, Jalisco, Mexico. We hypothesized that, because of their natural regeneration and greater plant diversity, secondary forest soils would have higher fertility and enzyme activities than pasture soils and would be more similar to primary forest soils. We predicted also that enzymes would be better indicators of land‐use effects on soil fertility than nutrients. Only one nutrient, available phosphorus, and one enzyme, acid phosphatase, were significantly and consistently affected by land use. As expected, these parameters were greater in primary and secondary forests than in pastures. Principal components analysis using all variables placed secondary forests intermediate between primary forests and pastures, as predicted, and total C, N and P, available P, ammonium, phosphatase, urease and the C:P ratio were the variables associated with this spatial arrangement of land uses. We conclude that secondary forest soils showed improved fertility and were overall closer to primary forests than to pastures in most variables measured.     

长江三角洲地区土地利用方式变化的特征及其过程

As one of the developing countries China has an arable land per capita far below the world‘s average level.With a high-density population an the quick development of economy and urbaniztion,the Yangtze River Delta shows the typical characteristics of land use in developed regions of China,which are:high land reclamation rate and low arable land per capita;intensive land use and high output value;and rapid increasing of construction land area and fast diminishing of arable land.The analysis indicates that the process of the arable land changes in the Yangtze River Delta could be divided into four different change stages over the past 50 years.     

Kinetics of phosphorus release from calcareous soils under different land use in Iran

The rate of phosporus (P) release from soils can significantly influence P fertility of soils. The objectives of this study were to investigate the effects of land‐use types on the kinetics of P release under different management practices and the relationship between kinetic parameters and soil physical and chemical properties from calcareous soils. The kinetics of P release in 0.01 M CaCl₂ was studied in surface samples of 30 calcareous soils planted to garlic, garden, pasture, potato, vegetables, and wheat. Trend in P‐release kinetics was similar between land‐use types. Significantly different quantities of P were released under different land use. The maximum amount (average of five soils) (46.4 mg kg^–1) of P was released in soil under potato and the minimum amount (10.4 mg kg^–1) under pasture. The kinetics of P release from soils can be described as an initial rapid rate followed by a slower rate. Different models were used to describe P release. In general, parabolic diffusion and power equation were found to be appropriate for modeling P release. The P‐release rate for the soils was estimated by parabolic equation for the studied land‐use types. The constant b was lower for pasture and wheat than for garlic and potato. The relationship between the rate of P release with Olsen‐P was linear, while it was curved with respect to the CaCl₂‐P, indicating that release of P was diffusion‐controlled. When the kinetic parameters of models were regressed on soil properties, CaCl₂‐P and CaCO₃ appeared to be the most important soil properties influencing P‐release rates in these soils.     

Land use change and land degradation in China from 1991 to 2001

China has long been experiencing intense land use/cover changes (LUCC). Undesirable land use/cover changes have resulted in widespread land degradation. This study examines the temporal and spatial dynamics of land use change and land degradation as evident from land use survey datasets (1991–2001). Six prominent land degradation processes were identified, namely: desertification, secondary salinisation, loss of agricultural use, deforestation, grassland degradation and loss of wetland. Rates of conversion were calculated and distribution patterns were mapped with the aid of GIS. The results showed that these land use changes have affected the wider environment and accelerated land degradation. It provided a more complete and up‐to‐date picture of China's land degradation which helps to develop improved conservation policies that combat land degradation and promote sustainable land management. Copyright © 2006 John Wiley & Sons, Ltd.     

黄土高原半干旱区不同土地利用下的土壤有机碳、碳组分和土壤营养

Cropland (CP), native grassland (NG) and two shrub land treatments which were converted from cropland in 1985:seabuckthorn (Hippophae rhamnoides L. ) (ST), and branchytamarisk (Tamarix ramosissima) (BT) were investigated to evaluate effects of land use conversion on soil organic carbon (SOC) and soil nutrients in the semi-arid region of the Loess Plateau of China. Total organic carbon (TOC), light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), total N (TN), nitrate nitrogen (NO₃^--N) and nitrite nitrogen (NO₂^--N), ammonium nitrogen (NH₄⁺-N), total P, and available P (AP) were measured. The results showed that SOC in NG, ST and BT were 12.7%, 27.7% and 34.8% higher than that of the cropland, respectively. LFOC, light fraction (LF) dry matter, ratio of TOC to TN (C/N) and the ratio of TOC to AP (C/P) were higher in the shrub land or native grassland than in the cropland. Cropland had the highest TN, the sum of NO₃^--N and NO₂^--N, TP and AP due to the use of chemical fertilizers. TOC significantly correlated with LFOC, HFOC and C/N. LFOC significantly correlated with dry matter of the LF and C/N. TN, the sum of NO₃^--N and NO₂^--N and AP were significantly negatively correlated with TOC and LFOC. Therefore, land use conversion from cropland to shrub land, or maybe grassland, contributed to SOC sequestration and improved soil nutrients stabilization.     

重庆市土地利用变化特征的遥感分析（英）

使用TM影像和参与性农村评估获取的数据,研究了1986-2005年间重庆市土地利用变化的时空特征,结果表明:1986-1997年间,耕地转为建设用地、草地和未利用地开垦为耕地或林地是重庆市3个最大的土地转换类型,而1997-2005年,这一转换则体现为耕地退为林地、建设占用耕地、耕地转换为水体和未利用地开垦为耕地或林地.建设用地的扩张以耕地的减少为代价,而同时又有大量的草地和未利用地开垦成耕地.林地的快速增加来源于草地和未利用地的开发和建设用地的复垦.同时,三峡工程的修建也使得沿江及其支流的部分耕地转换为水域.然而,驱动重庆土地利用变化的这一特征,其主要原因在于政策安排和土地利用覆盖的原始格局.前者决定短时期内重庆土地利用变化的基本方向,而后者则在大的环境背景下,决定重庆土地利用变化异质性的根本性力量.研究有助于理解后备资源短缺下的土地资源压力,对制定合适的土地管理时间策略,监测生态系统状况和态势具有重要意义.