浙江省土地退化及防治对策

浙江省属湿润季风亚热带气候区，地形以丘陵山地为主，土地退化严重，主要方式有水土流失，土地污染及土地养分贫瘠化，本文根据土地退化现状，提出了基本的防治对策。

生防菌剂对不同连作障碍强度土壤上辣椒的影响

研究生防菌剂对不同连作障碍强度土壤上辣椒的影响,结果表明:生防菌剂天绿可提高连作障碍土壤中的有效养分,增强土壤肥力,促进连作障碍土壤上辣椒的正常生长发育,提高辣椒产量。

On Spatial Variability and Distribution of Soil Nutrients in Different Nitraria tangutorum Bobr.Populations in Tsaidam Basin

In this paper,six important distribution areas of Nitraria tangutorum Bobr.in Tsaidam Basin were selected as research objects,to study spatial variability and distribution of soil nutrients in different N.tangutorum populations and analyze the relationship between soil nutrient contents and geographical location,by measuring soil pH and the contents of organic matter（OM）,total nitrogen（N）,total phosphorus（P）,total potassium（K）,hydrolysis N,available P and available K in soils.Results showed that：（1） soil nutrient contents among different populations showed significant spatial variability,and soil depth had a significant effect on soil nutrients contents,but the variation rules were not obvious.（2）Average pH and average contents of OM,total N,total P,total K,hydrolysis N,available P and available K in soils with different depths（0-15,15-30,30-45 cm） varied in the range of 8.37-9.21,3.34-20.68,0.18-1.21,0.35-0.75,16.12-22.04,5.13-553.28,1.10-52.54 and 103.83-562.28 mg/kg,respectively.（3） The analysis results of correlation between average values of pH and contents of nutrient indexes in soils with different depths（0-15,15-30,30-45 cm） showed that the correlation of these indexes were different.（4）OM and total N contents in soils with different depths（0-15,15-30,30-45 cm） all had a significant positive correlation with latitude and negative correlation with longitude and altitude,and the correlation of available P and available K contents in surface soils（0-15 cm） with latitude,longitude and altitude were significant positive,significant negative and significant negative,respectively;moreover,longitude and latitude also showed a significant impact on soil available K contents with the depth of 30-45 cm.In addition,comprehensive analysis result of nutrient contents showed that N.tangutorum populations in Huaitou Tala Town had the highest fertility,and the fertility levels of N.tangutorum populations in Chaka Town and Wulan Keke Town were relatively lower.

Effects of Vegetation Restoration in Different Types on Soil Nutrients in Southern Edge of Mu Us Sandy Land

In order to explore effects of vegetation on nutrients in soils, nutrients characters of soils under natural grass, closed grass, abandoned lands, forest lands returned from farmlands and fixed sandy areas in Mu Us Desert were researched. The results indicated that vegetations in varied types have different effects on organic matter, total N, available N and available P, among which the first three were all higher in soils under closed grass, forest lands returned from farmlands, and fixed sandy lands than those under natural grass and abandoned lands. This was totally contrary with contents of available P in soil. In addition, nutrients in soils at 0-20 cm were more influenced by vegetation, than those at 20-60 cm, and Caragana Korshinskii proved better in improving nutrients in soils.

Study on Status quo of Nutrients in Soils of Farmlands in Gonggar County and Related Countermeasures

[Objective] The aim was to analyze nutrients distribution and proportion in soils of farmlands of Gonggar County in Tibet. [Method] According to survey of soils in Tibet, nutrients of farmlands in Gonggar County were analyzed and the countermeasures were proposed to achieve sustainable development of nutrients in soils. [Result] In Gonggar County in Tibet, farmlands with insufficient and less organic matter occupy 58.38%; farmlands with moderate contents of total N occupy 47.71%; farmlands with insufficient and less alkali-hydrolyzable nitrogen represent 82.36%; the farmlands with moderate and rich total P take up 49.40% and 21.59% ; farmlands with insufficient and less rapidly available P represent 67.33%; farmlands with richer and rich total K occupy 76.14% ; farmlands with moderate and insufficient rapidly available K represent 72.21%. [Conclusion] Based on nutrients in soils of farmlands, the countermeasures for sustainable utilization of nutrients in farmlands are proposed, including increase of organic fertilizer, soil testing and formulated fertilization and adjustment of acid-base balance.

Soil Organic Carbon,Carbon Fractions and Nutrients as Affected by Land Use in Semi-Arid Region of Loess Plateau of China

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 (NO 3-N) and nitrite nitrogen (NO 2-N),ammonium nitrogen (NH + 4-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 NO 3-N and NO 2-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 NO 3-N and NO 2-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.

Relationship Between Water-Stable Aggregates and Nutrients in Black Soils After Reclamation

Water-stable aggregates, which are an index for the evaluation of the structural properties of the soil, are affected by many factors. Zhaoguang Farm, Longzhen Farm, and Jiusan Farm were chosen as the representative study sites in the region of black soils, a typical soil resource in Northeast China. The variation in the content of 〉 0.25 mm water-stable aggregates and its relationship with the nutrients in black soil were investigated after different years of reclamation. The results showed that the 〉 0.25 mm water-stable aggregates were more in the surface than in the subsurface soil and they changed in the following order： Longzhen Farm 〉 Zhaoguang Farm 〉 Jiusan Farm. The water-stable aggregates decreased sharply at the initial stage of reclamation and then became stable gradually with time. They were significantly correlated with the contents of organic C, total N, total P, and CEC in black soil, with the correlation coefficients r being 0.76, 0.68, 0.61, and 0.81 （P 〈 0.01）, respectively; however, their relationships with available P, available K, and total K were unclear. These showed that organic matter was the cementation of soil water-stable aggregates. Increasing decompositions and decreasing inputs of organic matter after reclamation were responsible for the amount of reduction of the water-stable aggregates. Thus, to maintain good soil aggregate structure, attention should be paid to improvement of soil nutrient status, especially the supply of organic C and N.

Degradation of Soil Nutrients in Southeast China

A total of 2 190 soil nutrient data in the Second National Soil Survey of China were collected to assess thedegradation of soil nutrients in the hilly region of Southeast China. The definition of soil nutrient degradationis suggested firstly then the evaluation criteria are set up and the current status of degradation of red soil and latosol is assessed. The percentages of areas in four grades of soil nutrient degradation, i.e., slightlydeficient, medium deficient, severely deficient and extremely deficient, were 21.3%, 43.3%, 16.2% and 3.0%for soil total N; 0.7%, 6.4%, 16.7% and 76.2% for soil available P; and 25.4%, 26.3%, 8.6% and 5.0% forsoil available K, respectively. The severity of soil nutrient degradation was in the order of P > N > K. Themajor factors leading to the degradation of soil nutrients in quantity include soil erosion, leaching and theconsumption by crops. And the principal faCtor affecting the degradation of soil nutrieots in availability isthe fixation of N, P and K, especially the fixation of phosphorus. The average amouat of P fixed by soils is408 mg kg-1, and upland soils can fix more P than paddy soils.

Distribution of Soil Nutrients in Arable Land of Tropical Hilly and Mountainous Area

[Objective] The aim was to explore spatial distribution characters of soil nutrients in arable lands of Hainan mountainous areas and provide references for soil nutrient management in tropical mountainous areas. [Method] The research took arable lands in Wuzhishan City as an example by field survey, sampling and lab analysis and investigated soil nutrients and distributions based on analysis of soil nutrient contents. [Result] The soils were dominated by acid soils, with pH of 5.1; soil nutrients were distributed in a non-uniform manner; contents of soil organic matter, available phosphorus, available potassium, as well as medium elements kept lower or moderate levels; effective copper and available zinc were rich. Local spe- cial climate, uneven distribution of parent material and non-uniform fertilization con- tributed to acid soils and unbalanced distribution of soil nutrients in Wuzhishan. [Conclusion] It is recommended to facilitate soil nutrient balance by promoting re- turning straws to farmlands and technical specification of balanced fertilization by soil testing as per nutrient distribution of arable lands in Wuzhishan City.

Soil Nutrient Variance by Slope Position in a Mollisol Farmland Area of Northeast China

In order to generate scientifically-based comparative information to improve fertilization efficiency and reduce nutrient loss, 610 samples of 122 soil profiles were collected at the 0–60 cm depth to compare soil nutrient contents including soil organic matter(SOM), total nitrogen(TN), total phosphorus(TP), available phosphorus(AP), and available potassium(AK) among different slope positions in a Mollisol farmland area of Northeast China. The contents of SOM and TN typically decreased with increased soil depth at back and bottom slope. Soil loss and deposition tended to decrease SOM and TN at the 0–20 cm soil depth on both the back slope and the slope bottom. The TP firstly decreased from 0–20 cm to 30–40 cm, and then not constantly increased at the back slope and the bottom slope. Due to the characteristics of soil nutrients and crop absorption, the contents of both AP and AK were typically the highest at the summit, followed by the slope bottom and the back slope in the 0–20 cm layer. Generally, in order to sustain the high soil productivity and protect the environment, attention should be paid to soil conservation on back slope; in addition, additional N and P fertilizer is necessary on the back slope.

Soil Nutrient Distribution in Two Typical Paddy Terrace Wetlands Along an Elevation Gradient During the Fallow Period

Soil nutrient concentrations in the top soils from two paddy terraces were determined in order to investigate spatial distributions of soil nutrients along the elevations on the Yunnan plateau of China during the fallow period.Results showed that soil nutrients in both terraces were higher than the reference concentrations except for SOC,TN,TP and Fe.Soil macronutrients didn't show significant differences in both terraces except for Mg and Ca,so did soil micronutrients except for Mn.Spatial distribution patterns of soil nutrients along the increasing elevations were different in both terraces.However,soil nutrients in both terraces were generally not significantly influenced by the elevations and soil pH values.The findings of this study can contribute to soil fertility management and ecological protection of Hani terraces.

Vertical Distribution and Seasonal Fluctuation of Nematode Trophic Groups as Affected by Land Use

A field investigation was conducted at the Shenyang Experimental Station of Ecology, Chinese Academy of Sciences, in an aquic brown soil of Northeast China under three land use types (cropland, abandoned cropland, and woodland) in order to evaluate whether the vertical distribution and seasonal fluctuation for the number of total nematodes and trophic groups could reflect soil ecosystem differences and to determine the relationships between soil chemical properties and soil nematodes. The majority of soil nematodes were present in the 0-20 cm soil layers, and for these land use types plant parasites were the most abundant trophic group. In the abandoned cropland the numbers of plant parasites reached a peak on the August sampling date, whereas the cropland and woodland peaked on the October sampling date. Meanwhile, in all land use types the number of total nematodes, bacterivores, plant parasites, and omnivores-predators was negatively (P < 0.05, except for bacterivores in cropland, which was not significant) correlated with bulk density, and positively (P < 0.05, except for fungivores in abandoned cropland, which was not significant) correlated with total organic carbon and total nitrogen.

Effects of Different Types of Chinese Fir Stands on Nu－trient Status of Soils

The effects of different types of Chinese fir stand, including those with various composition (pure andmixed), in various cropping systems (first and continuous cropping system) and at different ages, on thenutrient status of soils in the hilly regions of southern Anhui Province were studied by means of ecologicalsequential comparison on the basis of similar climate and soil type. The work was carried out in the XiaoxiForest Farm of Jingxian County and the Caijiaqiao Forest Farm of Jingde County, where the soil is parayellowsoil derived from phyllite and sandstone. The results revealed that with the increase of age, Chinese fir purestand could accumulate organic matter and nitrogen in the soil but it resulted in decreasing of soil PH and baseions (especially Ca￣(2+)) compared to its mixed stand with broad-leaf trees such as Chinese sassafra.s. In orderto improve the soil fertility, it would be better to mix Chinese fir with broad-leaf trees when afforestation.In the management of Chinese fir pure stand, base compounds and phosphates should be added to the soilfor maintaining soil fertility and raising forest productivity.

Impact of soil texture and sweetpotato cropping system on soil erosion and nutrient loss in the Three Gorges Reservoir Area of the Changjiang River

This study investigated the impact of soil texture and sweetpotato cropping system on soil erosion and nutrient loss in the drought infield of the Three Gorges Reservoir Area of Changjiang River under field conditions. A factorial experiment was conducted in the study using five soil textures and two cropping systems. The lost soil during the crop season was recovered by a soil-blocking device and the dry weights for the total lost soil and its nutrient components, such as ammonium nitrogen, effective phosphorus, K^＋ and organic matter were analyzed. We found that soil texture significantly affected the dry weights of the total lost soil, effective phosphorus, K^＋, and organic matter, while sweetpotato cropping systems and interaction between soil texture and sweetpotato cropping system affected the dry weights of the total lost soil, the effective phosphorus and organic matter. Among the five soil textures tested, Da and Huang caused significantly less soil erosion and nutrient loss compared with the other three soil textures; intercropping sweetpotato with corn significantly reduced soil erosion and nutrient loss.

Soil Organic Carbon and Nutrients along an Alpine Grassland Transect across Northern Tibet

Soil carbon and nutrient contents and their importance in advancing our understanding of biogeochemical cycling in terrestrial ecosystem, has motivated ecologists to find their spatial patterns in various geographical area. Few studies have focused on changes in the physical and chemical properties of soils at high altitudes. Our aim was to identify the spatial distribution of soil physical and chemical properties in cold and arid climatic region. We also tried to explore relationship between soil organic carbon （SOC） and total nitrogen （TN）, total phosphorus （TP）, available nitrogen （AN）, available phosphorus （AP）, soil particle size distribution （PSD）. Samples were collected at 44 sites along a 300 km transect across the alpine grassland of northern Tibet. The study results showed that grassland type was the main factor influencing SOC, TN and TP distribution along the Gangdise Mountain-Shenzha-Shuanghu Transect. SOC, TN and TP contents were significantly higher in alpine meadow than alpine steppe ecosystems. SOC, TN, TP and AN contents in two soil layers （0-15 cm and 15-3o cm） showed no significant differences, while AP content in top soft （0-15 cm） was significantly higher than that in sub-top soil （15-30cm）. SOC content was correlated positively with TN and TP content （r = 0.901and 0.510, respectively）. No correlations were detected for clay content and fractal dimension of particle size distribution （D）. Our study results indicated the effects of vegetation on soil C, N and P seem to be more important than that of rocks itself along latitude gradient on the northern Tibetan Plateau. However, we did not found similar impacts of vegetation on soil properties in depth. Inaddition, this study also provided an interesting contribution to the global data pool on soil carbon stocks.

Application of Matter-element Model in Soil Nutrient Evaluation of Ecological Fragile Region

On the basis of the soil environment investigation in Da＇an City, Jilin Province, China, 40 soil samples from main land use types were obtained and tested by standard method. Soil organic matter （SOM）, total N （TN）, total P （TP）, total K （TK）, available N （AN）, available P （AP） and available K （AK） were chosen as the evaluation factors. A regional soil nutrient evaluation model was developed based on the matter-element model. The results show that the soil samples with nutrient grade Ⅱ-Ⅴ respectively account for 10%, 30%, 32.5% and 27.5%, and those with grade Ⅳ and Ⅴ account for 60% in all samples. The relationship between soil nutrients and land types indicates that the nutrients of farmland are relatively good, with 41.7% of soil samples with the nutrient grade Ⅳ and Ⅴ. The nutrients of saline-alkali land and sandy land are the worst, with 100% of soil samples with the nutrient grade IV and V. And the ratios of soil samples grade IV and V in grassland and wasteland are respectively 62.5 % and 54.55%. Generally speaking, the soil nutrients status in Da＇an City is poor, 60% of soil samples are in poor and extremely poor conditions, indicating that the soil has been severely eroded. Being a relatively superior evaluation method with more accurate resuits and spatial distribution consistency, matter-element analysis is more suitable for regional soil nutrient evaluation than previous models.

Comparative analysis of some selected macronutrients of soil in orange orchard and degraded forests in Chittagong Hill Tracts,Bangladesh

Status of organic carbon (C), total nitrogen (N), available potassium (K), calcium (Ca) and phosphorus (P) in three different depths (0-5 cm, 5-15 cm and 15?30 cm) on two hill slopes of 35% and 55% in orange orchard cultivated by the Mro tribe of Chittagong Hill Tracts (CHTs) were evaluated and compared with those in degraded bush forests, through digging three profiles in each land use. The content of all the five nutrients was found to be higher in the soil of orange orchard than in the soil of forest. But the variation was not consistent for both the slopes. The content varied depth wise also, having the highest value in surface soil in case of both the land uses on both the slopes. A mean available K content was significantly higher in orange orchard than in forest on 55% slope, while it was lower on 35% slope. Surface soil contained the nutrients of K and Ca with the amount of 0.2905-mg·g^(-1) soil and 3.025-mg·g^(-1)soil respectively in the orchard, while 0.1934-mg·g^(-1) soil and 1.6083-mg·g^(-1) soil were respectively in the forest. Organic carbon and total nitrogen were found more or less similar in surface soil on both the land uses showing a slight difference. Available P was found only in orange orchard, and in forest it was too little in amount to detect by the spectrophotometer. The degraded forests were poor in nutrient content due to high rate of soil erosion, which would be possible to be improved by bringing it under tree cover as proved by the adaptation of orange orchard there.

Efficiency of Biological Nitrogen Fixation of Bradyrhizobium under Different Soil Fertility Levels as Measured by 15N Dilution Analysis

The objective of this study was to determine the efficiency of biological nitrogen fixation （BNF） of local Bradyrhizobium isolates in soil of various fertility levels using 15N dilution technique. Local isolates were obtained from cowpea rhizosphere in fields of different Iraqi provinces. Six isolates were selected in this study, which was conducted as a pot experiment under greenhouse conditions. Effects of the following fertility levels were evaluated： at F1, 0 mg N, P and K was added; at F2, 25 mg N/kg soil, 10 mg P/kg soil and 25 mg K/kg soil were added, respectively; the other two levels were F3 at which 50, 20 and 50 mg/kg soil and at F4 75, 30 and 75 mg/kg soil for N, P and K, respectively, were added. Urea, labeled with 15N 10% access atom （aa）, was used as a source of N. The highest BNF was observed under the lowest fertility level, i.e., F1. BNF across all isolates was markedly decreased with the increase of nutrient application to soil, being totally eliminated at the highest fertility level F4. Numbers of nodules per plant root of all isolates were the least under the zero nutrients application and the highest nodules number were found under the highest levels of N, P and K application. Number of nodules does not necessarily reflect the best BNF efficiency of all isolates. However, fertility levels were of significant effect on average nodule number of all isolates. The lowest plant dry weight was under the first fertility level F1 irrelevant of Rhizobium isolates. In general, the highest plant dry weight was under the second soil fertility level F2.

Spatial Variability Analysis of Soil Nutrients Based on GIS and Geostatistics:A Case Study of Yisa Township, Yunnan, China

Hani rice terraces system is one of the Globaly Important Agricultural Heritage Systems （GIAHS） pilot sites selected by FAO. Soil nutrients are an important symbol of soil fertility, and play an important role in the sustainable utilization of land. Based on geo-statistics and GIS, the spatial variation of pH, organic matter, total nitrogen, alkaline hydrolyzable nitrogen, available phosphorus and available potassium in the soil in Yisa （a town in Honghe County, Yunnan Province） was studied. The results show that the spatial variability of pH, organic matter, total nitrogen, alkaline hydrolyzable nitrogen and available potassium exhibited medium spatial variability, and the coefficients of variation are 12.54%, 40.14%, 40.00%, 34.89%, and 40.00% respectively. Available phosphorus exhibited strong spatial variability, and the coefifcient of variation is 102.13%. The spatial variation of pH, organic matter, total nitrogen, alkaline hydrolyzable nitrogen and available potassium fit the index mode, however, the spatial variation of available phosphorus ifts the spherical model. Total nitrogen, available phosphorus and available potassium were greatly affected by soil structural factors, while pH, organic matter and alkaline hydrolyzable nitrogen were affected by both structural and random factors. The spatial distribution of soil nutrients in Yisa was intuitively characterized by Kriging interpolation. It is very important to understand the spatial distribution of soil nutrients, which wil provide the guidance for adjusting agricultural management measures such as fertilization.