中国杉连作对土壤肥力的影响

The changes in soil fertility under continuous plantation of Chinese fir were studied by comparing soil samples from different forest stands:the first and second plantations of Chinese fir,evergreen broad-leaved forests,and clear-cut and burnt Chinese fir land located at Xihou Village,Nanping of Fujian Province.The soils were humic red soil originated from weathered coarse granite of the Presinian system.Soil pH,CEC,base saturation ,exchangeable Ca^2 ,exchangeable Mg^2 and A1-P declined after continuous plantation of Chinese fir.The same trends were also found in the soils under broad-leaved stands and slash burnt lands.The explantation was that not merely the biological nature of the Chinese fir itself but the natural leaching of nutrients,soil erosion and nutrient losses due to clear cutting and slash burning of the preceduing plantation caused the soil deterioration .Only some of main soil nutrients decreased after continuous plantation of Chinese fir,depending on specific silvicultural system,which was different from the conclusions in some other reports which showed that all main nutrients,such as OM,total N,available P and available K decreased,Some neccessary step to make up for the lost base,to apply P fertilizer and to avoid buring on clear cut lands could be taken to prevent soil degradation and yield decline in the system of continuous plantation of Chinese fir.     

黄土高原某些耕作土壤中土壤微生物生物量C、N与矿化N的关系

The chloroform fumigation-incubation method was used to measure the soil microbial biomass C (SMBC) and N (SMBN) in 16 loessial soils sampled from Ansai, Yongshou and Yangling in Shaanxi Province. The SMBC contents in the soils ranged from 75.9 to 301.0 μg C g^-1 with an average of 206.1 μg C g^-1, accounting for 1.36%~6.24% of the total soil organic C with an average of 3.07%, and the SMBN contents from 0.51 to 68.40 μg N g^-1 with an average of 29.4 μg N g^-1, accounting for 0.20%~5.65% of the total N in the soils with an average of 3.36%. A close relationship was found between SMBC and SMBN, and they both were positively correlated with total organic C, total N, NaOH hydrolizable N and mineralizable N. These results confirmed that soil microbial biomass had a comparative role in nutrient cycles of soils.     

中国云南省滇池盆地东南区由于土地利用方式的变化（从水田变为旱地或温室土壤）导致土壤理化性质的变化研究

Paddy fields in the southeastern basin of Dianchi Lake have rapidly changed to greenhouses since 1999. A total of 61 surface soil samples, including 43 greenhouse soils, 12 upland soils, and 6 paddy soils, were collected from a flat lowland area mainly used for agricultural production fields in the southeastern basin of Dianchi Lake. Analyses of the soil samples indicated that the greenhouse soils were characterized by a lower organic matter content, lower pH, and higher soluble nutrients than the paddy soils in the area. The lower organic matter content of the greenhouse soils was ascribed to environmental or management factors rather than the clay content of the soil. Accumulation of soluble nutrients, especially inorganic N, was due to over-application of fertilizers, which also caused soil acidification. The average amount of readily available N, P, and K accumulated in the greenhouse soils was estimated to be equal to or higher than the annual input of these nutrients as a fertilizer, indicating that a reduction in fertilizer application was possible and recommended. In contrast, a very low available Si content was observed in the paddy soils, suggesting the need for Si application for rice production.     

Human Activity and Soil Fertility-Nutrients Depletion of Arable Soils in China

The reserve of soil nutrients is limited.In case of irrational use of land,nutrients would be depleted sooner.Before the 1950s the low grain production in China was maintained only by expanding the cultivated area and by recycling of nutrients in agriculture.Calculation of nutrients balance showed that in the year of 1949 there were great deficits of N,P and K elements in agriculture of China.It revealed that there would have really been danger of soil nutrients exhaustion if such a situation had continued.Things have changed since the beginning of 1950s.The nutrients balance in agriculture has been getting better and better.In the year 1987 N and P balance got rid of their great deficits.But for K and deficit grew even larger.This resulted in a rapid expansion of soil area deficient in K in China since the mid 1970s.In spite of the fact that the P balance in the arable land of the whole country was positive,the field which did not receive P fertilizer had become deficient in P.So the area deficient in P also increased.It is stressed that great attention should be paid to the depletion of soil nutrients,especially K in the northern part of China where the soil is relatively rich in K.Of course,soil sulfur and microelements should be considered next.     

在施钾条件下灌溉水稻的养分吸收和利用效率研究

Potassium is one of the most important nutrients for rice production in many areas of Asia, especially in southeast China where potassium deficiency in soil is a widespread problem. Field experiments were conducted for four consecutive years in Jinhua City, Zhejiang Province, to determine utilization of nutrients (N, P and K) by inbred and hybrid rice and rice grain yields as affected by application of potassium fertilizer under irrigated conditions. Grain yield and nutrient harvest index showed a significant response to the NPK treatment as compared to the NP treatment. This suggested that potassium improved transfer of nitrogen and phosphorus from stems and leaves to panicles in rice plants. N and P use efficiencies of rice were not strongly responsive to potassium, but K use efficiency decreased significantly despite the fact that the amount of total K uptake increased. A significant difference between varieties was also observed with respect to nutrient uptake and use efficiency. Hybrid rice exhibited physiological advantage in N and P uptake and use efficiency over inbred rice. Analysis of annual dynamic change of exchangeable K and non-exchangeable K in the test soil indicated that non-exchangeable K was an important K source for rice. Potassium application caused an annual decrease in the concentration of available K in the soil tested, whereas an increase was observed in non-exchangeable K. It could be concluded that K fertilizer application at the rate of 100 kg ha^-1 per season was not high enough to match K output, and efficient K management for rice must be based on the K input/output balance.     

中国东南部红壤地区不同植被对土壤侵蚀和土壤养分的影响

The effect of different vegetation systems including bamboo plantation (BP), forest ecosystem (CF), citrus orchard (Ctr) and farmland (FL) on erosion and nutrients of red soil were investigated in hilly region of southeastern China to find effective control measures for soil erosion. The results showed that all the vegetation systems could significantly reduce soil erosion and nutrient losses compared to bare land (Br). The ability of different vegetation systems to conserve soil and water was in the order of Ctr > BP > CF > FL > Br. Vegetation could also improve soil fertility. The soil organic matter, total N and total P contents were much higher in all the vegetation systems than in bare land, especially for the top soils. Vegetation systems improved soil physical properties remarkably. Compared to the bare land, soil organic matter, TP, TK and available K, especially soil microbial biomass C, N and P, increased under all the vegetation covers. However, they were still much lower than expected, thus these biological measurements are still needed to be carried out continuously.     

黑土开垦后水稳性团聚体与土壤养分的关系

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.     

土壤非交换态钾与结构态钾能够区分吗?（英文）

Nonexchangeable K(NEK) is the major portion of the reserve of available K in soil and a primary factor in determining soil K fertility.The questions of how much NEK is in soils and how to quantify total NEK in soils are so far still unclear due to the complicated effects of various minerals on K fixation.In this study,the NEK in 9 soils was extracted with sodium tetraphenylboron(NaBPh_4) for various time periods longer than 1 d.The results showed that the NEK extracted by NaBPh4 gradually increased with time,but showed no more increase after the duration of extraction exceeded 10-20 d.As the temperature increased from 25 to 45 ℃,the duration to obtain the maximum extraction of NEK was reduced from 20 to 10 d,and the maximum values of NEK released at both temperatures was almost the same for each soil.The maximum NEK(MNEK) of the 9 soils extracted by NaBPh.4 varied from3074 to 10081 mg kg~(-1),accounting for 21%-56%of the total soil K.There was no significant correlation between MNEK released by NaBPh4 and other forms of K,such as NH_4OAc-extracted K,HNOg-extracted K and total K in soils,which indicates that NEK is a special form of K that has no inevitable relationship to the other forms of K in soils.The MNEK extraction by NaBPh4 in this study indicated that the total NEK in the soils could be differentiated from soil structural K and quantified with the modified NaBPlu method.The high MNEK in soils made NEK much more important in the role of the plant-available K pool.How to fractionate NEK into different fractions and establish the methods to quantify each NEK fraction according to their bioavailability is of great importance for future research.     

在土壤不受干扰条件下N矿化2/3规律研究

It is reported in literature that globally, only about two-thirds of N in nutrient sources is available to plants and microbes in soils under undisturbed conditions. The present study explores this phenomenon and suggests a new theory to explain this. Diffusion of NH4^＋ from microsite sources is considered here and analyzed for a capillary of the soil system. It has been found that 68% of NH4^＋ diffused from the nutrient source is initially preserved in the proximity of the nutrient source, whereas, the remaining 32% is diffused away from the nutrient source and possibly immobilized in the nonexchangeable abiotic pools or lost. The NH4^＋ that has been initially retained near the microsites is gradually released to the mineral pool. Thus, about two-thirds of NH4^＋ released from microsites is available only to plants and microbes in the soil. This is a universal, natural mechanism of nutrient conservation for plant and microbial availabilities. The theory has important implications and applications in recommending N fertilizations in the forms of organic or mineral sources to plants grown across various soil textures, for which further studies are needed. Any deviations from this theory can mainly be attributed to various disturbances to the soil; for example, mechanical disturbances, nutrient leaching, and variations in pH and soil faunal activities. This theory may apply to other elements mineralized in the soils under undisturbed conditions, which must be investigated in future studies.     

Clay Addition to Sandy Soil——Influence of Clay Type and Size on Nutrient Availability in Sandy Soils Amended with Residues Differing in C/N ratio

Addition of clay-rich subsoil to sandy soil results in heterogeneous soil with clay peds(2-mm) or finely ground( 2 mm) clay soil(FG), which may affect the nutrient availability. The aim of this study was to assess the effect of clay soil particle size(FG or peds)and properties on nutrient availability and organic C binding in sandy soil after addition of residues with low(young kikuyu grass,KG) or high(faba bean, FB) C/N ratio. Two clay soils with high and low smectite percentage, clay and exchangeable Fe and Al were added to a sandy soil at a rate of 20%(weight/weight) either as FG or peds. Over 45 d, available N and P as well as microbial biomass N and P concentrations and cumulative respiration were greater in soils with residues of KG than FB. For soils with KG residues,clay addition increased available N and initial microbial biomass C and N concentrations, but decreased cumulative respiration and P availability compared to sandy soil without clay. Differences in measured parameters between clay type and size were inconsistent and varied with time except the increase in total organic C in the 53 μm fraction during the experiment, which was greater for soils with FG than with peds. We concluded that the high exchangeable Fe and Al concentrations in the low-smectite clay soil can compensate a lower clay concentration and proportion of smectite with respect to binding of organic matter and nutrients.     

喀斯特山区土地利用方式对土壤质量演变的影响

通过调查喀斯特山区典型土地利用方式对土壤养分和土壤容重的影响 ,结果表明 ,森林的破坏以及随后的耕种显著增加了土壤容重 ,并降低了大部分土壤养分。和林地相比 ,灌木林、灌丛、草地和退耕 3年的蒿草地容重分别增加了 32 % ,2 0 .3% ,4 6 .9% ,5 2 .3%。除全钾外 ,草地和退耕蒿草地土壤养分显著下降 ,和林地相比 ,草地有机质减少了 2 9.3% ,全氮减少了 4 8.2 % ,全磷减少了 6 6 .3% ,碱解氮减少了 4 5 .8% ,有效磷减少了 5 6 .3% ,有效钾减少了 6 0 % ;退耕 3年的蒿草地土壤有机质、全氮、全磷、碱解氮、有效磷和有效钾分别减少了 85 .6 % ,84 .7% ,81.4 % ,74 .9% ,87.5 %和 90 .6 %。土壤退化指数的计算结果表明 ,草地和退耕蒿草地发生了非常严重的退化     

坡耕地不同水土保持措施下的养分平衡和土壤肥力变化

在贵州省罗甸县坡耕地上布置长期定位试验 ,研究几种水土保持措施对作物产量和土壤肥力变化的影响。9年的测试结果表明 ,在旱坡耕地上 ,水土流失是造成坡地地力下降、养分损失 ,的主要原因。未采用水土保持措施的坡地种植 ,因水土流失产生的全氮、全磷、有效钾损失 ,分别占总养分消耗量的 5 3.0 % ,6 7.6 %和 19.0 % ,相当于施入土壤的氮素化肥 ,施入的有机和无机磷素 ,有机质的损失与施入的有机肥中有机质含量相当 ,土壤全氮、有机质和有效钾含量趋于下降 ,全磷维持在较低的水平。采取水土保持措施后 ,这些土壤养分可维持平衡或在土壤中逐步积累 ,试验中的植物篱水保处理 ,9年玉米产量平均增产 8.6 % ,并趋于逐年上升。长期的试验证明 ,采用适宜的水土保持措施可提高地力 ,增加产量 ,实现坡耕地的可持续利用     

我国土壤氮、磷、钾的基本状况

本文根据我国建国以来主要的研究结果对我国土壤氮、磷、钾的基本状况进行了概略的阐述。我国土壤氮磷钾含量的变幅：N是0.04-0.38%；P是0.017-0.11%；K是0.05-2.50%。耕地土壤几乎全部都需补给氮素，大约有1/2-1/3缺磷；1/4-1/3缺钾。缺钾土壤主要分布在长江以南，但北方土壤的缺钾问题也需要及时注意。成土母质、风化程度和人为的耕作施肥措施是影响土壤氮、磷、钾状况的主要因素。     

丘陵红壤耕作利用过程中土壤肥力的演变和预测

通过区域尺度上两个时段的定位采样 ,结合田块尺度上的长期试验 ,研究了耕作利用变化对我国中亚热带低丘红壤区土壤肥力演变的影响。分析了土壤肥力演变的驱动力 ,建立了土壤养分变化与养分平衡间的相关预测模型。对比分析表明 ,丘陵红壤肥力的变化与养分平衡量的变化趋势一致。在保持荒地和水田利用方式时 ,土壤有机质含量显著降低 ;旱地系统中速效磷和速效钾含量增加 ,但在不施肥的针阔混交林中却下降 ;荒地开垦为水田后 ,土壤肥力有增加趋势。旱坡地红壤全氮和速效钾的变化量与氮、钾的平衡量的显著相关 ,而土壤速效磷与磷的平衡量间相关不显著 ,其原因是没有考虑磷的固定和矿化。     

土壤养分状况系统研究法及其应用初报

本文介绍了一个土壤养分状况系统研究方法，该方法包括土壤样品１１种元素的速效含量测定、土壤对７种营养元素的吸附试验、盆栽试验和田间试验。应用该方法研究了１０４个土壤养分状况，盆栽试验发现１００个土壤缺氮，１０１个缺磷，６０个缺钾，３８个缺锌，２３个缺硫，２２个缺硼，分别有１９、１８、１４、１３、１１和３个土壤缺钼、钙、镁、铜、锰和铁。盆栽试验得到的结果在部分土壤的田间试验中得到了验证。     

人为干扰对典型草原生态系统土壤养分状况的影响

从土壤N，P，K及土壤有机质等方面研究了人为干扰（包括放牧、开垦和禁牧）对典型草原生态系统土壤养分含量的影响。研究结果表明：开垦和放牧会导致土壤，主要是表层土壤养分含量的下降，而开垦对土壤养分的影响更为明显；禁牧会提高土壤各种养分的含量，而且随着禁牧时间的增加，土壤养分含量有逐渐增加的趋势。对深层土壤养分含量没有明显影响。同时，草原生态系统土壤全氮、速效氮及有机质含量与土层深度呈明显的负直线相关关系；速效K、速效P含量则与土壤深度的关系符合二次幂函数关系；全磷含量随深度的增加有逐渐升高的趋势；土壤全钾含量随土壤深度的增加呈微弱的降低趋势，但变化不明显。本研究表明，禁牧可以提高典型草原土壤养分元素的含量，有利于遏制草原土壤的退化。     

The cost of soil lost from fields due to removal on harvested sugarbeet: a case study in Turkey

Abstract. Soil removed on sugarbeet ( Beta vulgaris L .) at harvest may be an important factor in soil degradation causing significant decline in soil productivity. This study evaluated soil losses on sugarbeet and estimated the cost of plant nutrients lost by this process. The losses were calculated using data from the agricultural reports published by the General Directorate of the Turkish Sugar Industry. Organic matter and plant available nutrient contents of soils removed from sugarbeet fields were determined. It was estimated that approximately 30 000 t of soil is lost annually in Erzurum, and 1.2 million t in the whole of Turkey. The cost of N, P and K losses is approximately 60 000 US$ annually for the study area.     

县级区域粮田土壤养分的空间变异性

采用传统统计和地统计相结合的方法 ,对面积约 470km2 的玉田县粮田耕层土壤养分进行了空间变异特征研究。结果表明 ,土壤N、P、K、Mn和Zn普遍缺乏 ,不同土壤养分的变异情况各不相同 ;土壤主要养分N、P、K、Mn和Zn含量的空间变异结构明显 ,在较大范围内存在着空间相关性 ,具有一定的渐变性分布规律 ,这一基本趋势对土壤养分分区管理是有利的     

Changes in soil aggregate‐associated enzyme activities and nutrients under long‐term chemical fertilizer applications in a phosphorus‐limited paddy soil

Paddy soils in subtropical China are usually deficient in phosphorus (P) and require regular application of chemical fertilizers. This study evaluated the effects of chemical fertilizers on the distribution of soil organic carbon (SOC), total nitrogen (N) and available P, and on the activity of the associated enzymes in bulk soil and aggregates. Surface soils (0–20 cm) were collected from a 24‐yr‐old field experiment with five treatments: unfertilized control (CK), N only (N), N and potassium (NK), N and P (NP), and N, P and K (NPK). Undisturbed bulk soils were separated into >2, 1–2, 0.25–1, 0.053–0.25 and <0.053 mm aggregate classes using wet sieving. Results showed that both NP‐ and NPK‐treated soils significantly increased mean weight diameter of aggregates, SOC, available P in bulk soil and aggregates, as compared to CK. Most SOC and total N adhered to macro‐aggregates (>0.25 mm), which accounted for 64–81% of SOC and 54–82% of total N in bulk soil. The activities of invertase and acid phosphatase in the 1–2 mm fraction were the highest under NPK treatment. The highest activity of urease was observed in the <0.053 mm fraction under NP treatment. Soil organic carbon and available P were major contributors to variation of enzyme activities at the aggregate scale. In conclusion, application of NP or NPK fertilizers promoted the formation of soil aggregates, nutrient contents and activities of associated enzymes in P‐limited paddy soils, and thus enhanced soil quality.