Abstract:Modern agriculture,as a modernizing stage of agricultural development, is the inevitable developmental trend of,Gins's contemporary agriculture. The developmental orientation of the modern agriculture of China is to take the way of intensive agriculture, i.e.,to strengthen intensive management, to stabilize food grain production and to persist in sustainable development. Under the future circumstances when facing serious challenges of population, resources and the environment, modern agriculture must contribute to providing human beings with sufficient and healthy food and a clear environment. The main problems challenging the development of the modern agriculture of China currently result from the sustainable development of agriculture and the construction of ecological environment as well as their interactions. To solve the problems, four main concepts should be consolidated and adopted, four principal contradictions should be solved, four key countermeasures should be intensified and four main relations should be well dealt with. Only by conscientious implementation of these policies can china's modern agriculture be developed further, thus making modern agriculture play a greater role in promoting the development of agriculture and economy in China.

Abstract:There are three soil types in South China Sea Islands, namely, Phosphic Lithomorphic Isohumisols, Holisols and Entisols, which are derived from bio-clastic and strongly calcareous sediments.In comparison with their parent materials, the Phosphic Lithomorphic Isohumisols have higher contents of P, Zn, Cu, Ba, and Cd, which tend to increase gradually with time, and lower contents of Mg, Ca, Sr, B, V, Pb, and Mo, which tend to decrease gradually with time. The above-mentioned constituents in Entisols and Holisols are similar to those in their parent materials except for P and Na, whose contents are higher than those in parent materials. The factors affecting element distribution are mainly special bioclimate and parent materials, which also result in the remarkable influence of soil-forming time on element distribution. Element availabilities of Phosphic Lithmorphic Isohumisols are characterized by enrichment in P, Zn, and Cu, and those of Holisols by enrichment in B. The factors affecting element bioavailabilities in soils are soil acidity, soil organic matter, cation exchange capacity and total element content, among which total element content has the strongest effect on P, Zn, and B availabilities, resulting that distribution of their element availabilites are similar to that of their total element contents.

Abstract:In this work, the characteristics of organic matter in different particle fractions of albic soil were studied by using Kumada's method. The results showed that the contnet of orc C in fertile soils and their particle fractions was higher than that in poor soil and it decreased with the increase of particle diameter. The decrement was smaller in fertile soil than that in poor soil. Soil organic matter and clay content the consistency between the storage curve of organic C and the content curve of particle fractions. Organic C storage of clay or fine sand particles in fertile soil was significantly higher than that in poor soil. The humus in soils and their particle fractions were mainly free form which can be extracted by 0.1 mol/L NaOH.Some indexes such as humic acid content and the PQ value of free form were higher in fertile soil than those in poor soil. But the degree of humification based on ΔlogK and RF values was lower in fertile soil.than that in poor soil. Those trends were much clear for silt and fine sand particles. With the increase of particle diameter, the contents of free humus and its humic acid. tended to decline, but the PQ₁ value was higher in silt particle than that in other particle fractions. The type of free humic acid changed with the increase of particle diameter in the order of A type (clay)→B type(silt)→Rp (fine sand). The content of combined humus which was extracted by 0.1 mol/L Na₄P₂O₇ and its humic acid content and the degree the humification were the highest in the silt particle, but PQ₂ decreased with the increase of particle diameter. Both in fertile soil and in poor soil combined humic acid mainly belonged to A type in which the degree of humification was higher, only a few belonged to B type or P type.

Abstract:The parameters of unrease kinetics were studied using sixteen samples from seven main soils in ShaanXi Province.The kinetic parameters (V_O、K_m、V_max、V_max、/K_m、K) and the active energy E_a could be used to express the characteristics of unease activity under different conditions of acology,and there were apparent differenoes between the soil samples of high and low fertility.Except for the paddy soil, the V₀,V_max,K and V_max、/K_m of urease in the high fertility soils are all greater than those in the low fertility soils. By means of correlation and principal component analysis, the kinetic parameters V_max、 and V_max、/K_m could act as the indexes of soil fertility;The sequence of average values of E_a showed a difference of enzyme reaction mechanism between high and low fertility soil samples.

Abstract:A salt water irrigation test was carried out to study soil salt-water dynamics and its effect on crop yields under conditionsof different salt water irrigation systems and to further study the suitable system of salt water irrigation in the Huqu irrigation area of Yuncheng Basin. The results show that the suitable quota of salt water imigation ranged from 825 to 975m³/ha and the suitable irrigation was 4 times in the area with a mineralization degree changing from 1 to 3g/L, 2~3 times in the area with a mineralization degree ranging from 3 to 5g/L, and 1 time in the area with a mineralization degree ranging from 5 to 7g/L.

Abstract:Fate of fertilizer N was investigated by the ¹⁵N mass balance method, and ammonia volatilization was measured by the micrometeorological technique after urea or ammonium bicarbonate was applied to spring wheat growing on a meadow chestnut soil at Zhangbei County, Hebei Province. The application rate of N fertilizer was totally 72.SkgN/ha, of which 1/3 was applied as basal dressing with seeding, and the rest 2/3 was applied as top dressing imn>adiately followed by irrigation.Results showed that plant recoveries, N remaining in 0-0.8m soil and total N losses of the applied N were 37.8%-48.3%, 33.8%-40.4% and 14.3%-25.4%, respectively. There was no apparent difference between the fates of urea N applied as basal dressing and top dressing. However, while N fertiliser was applied as top dressing, plant recovery was 10% higher from urea than from ammonium bicarbonate, and in contrast, N loss was 7.5% lower from the former than from the latter.volatilization was as low as 1% and 5% of the applied N when urea and ammonium bicarbonate were applied as top dressing, respectively. Results also showed that less than 1/3 of the N taken up by wheat was derived from the applied N fertilisers, and thus the rest was derived from the soil.

Abstract:Currently, in the Taihu region, the application of N fertilizer in the high-yielding paddy fields of rioewheat double cropping system averages around 520kg N per hectare per year.Experiments for years showed that N fertilization at a rate of 300kg N per hectare per year increased the crop yield significantly by 13.Skg of grain per kg of N applied, with the N recovery rate reaching 40.3%;but the increase was not significant at a rate of 450kg N, and 7.29kg of grain was increased by per kg of N applied with the N recovery rate dropping to 17.2% at a rate of 600kg N per hectare per year. In the last case, the N content in rice straws and sterility grain rate went up while the thousand-grain weight and the yield declined. Consequently, at the current yield level of 10-12 ton per hectare on the high yielding paddy field, the N fertilization rate was recommended to be at 375kg N per hectare per year,which could save 20-30% N-fertilizer as compared with the rate for large-area production.

Abstract:By a wind tunnel experiment with an aeolian sand soil sample collected from a field, a study was carried out to ascertain the wind erosion characteristics of the soil under reclamation. Two factors influencing soil wind erosion, surface destruction and vegetation coverage were studied. After a seies of laboratory work, the quantitative relationships between wind erosion rate and surface destruction rate and between wind erosion rate and vegetation coverage percentage were established. It was found that the former relationship complied approximately with a second power function, while the latter could be expressed by an exponential function.By means of computerized simulation the correlation between wind erosion rate and land reclamation rate was found to follow an exponential function. Furthurmore, some surface destruction, vegetation coverage and land reclamation thresholds are suggested to prevent aeolian sand soils from wind erosion, and some required soil conditions and measures of aeolian sand soils to be reclaimed for wind erosion control are pointed out in the present article.

Abstract:The results from a nine-year field experiment on a carbonate cinnamon soil indicated that the continuous low-input of phosphorus fertilizer with 14.4 kg P/ha annually could slighty increase soil Olsen-P and labile-P to the level as "non-deficiency" of phosphorus but far from setting up a large available phosphorus pool. The application of phosphorus fertilizer combined with recycled phosphorus from pig manure every year seemed to be able to set up a large available phosphorus pool finally. The role of phosphorus in pig manure was similar to that of fertilizer phos-phorus in improving soil available phosphorus pool. However, the application of phos-phorus every year with low dose was much better in increasing soil Olsen-P,labile-P and Ca₂-P than the treatment with high dose once every six years.

Abstract:The results showed that burning turf could accelerate the decomposition of organic matter, increase the available nutrient contents and raise grass output. But after 3-4 years of burning turf, the contents of available nutrients in the soil decreased obviously and the grass output dropped rapidly, Burning seriously destroyer the soil enzyme so that urease and protease activities could be recovered to 50-80% of the original levels, but alkaline phosphatase, catalase and invertase to only 20-40% of the original levels. Accumulation of organic matter and the activities of soil enzymes tended to be enhaned as time went on. In alpine meadow soil the enzymatic activities were closely related to organic matter content but little related to soil available nutrient content and grass output. So the content of organic matter and the activities of soil enzymes could not be taken as the indexes of soil fertility.

Abstract:A pot experiment was carried out to study the effects of two species of VAM fungi (Glomus sp.)on the vegetative growth and physiology of tea trees(Camellia sp.) and the quality of tea. The results showed that infection of host plants with mycorrhizal fungi markedly raised the activity of phosphorylase in the soil and the dehydrogenase of their roots, promoted the absorption of P, Cu and Mn, and increased their growth volumes and rates. In addition, the contents of chlorophyll and coffeine increased, but the activity of peroxidase and the contents of Fe and catechins reduced.

Abstract:黄土高原由于历史上森林砍伐过度,植被破坏严重,水土长期流失,导致当前农业生产干旱加剧、地力减退、水土流失严重。要从根本上使这一地区水、肥状况有所改善,就必须对传统耕作模式进行改革^[2,3],建立一套适应于高产优质高效农业的新耕作模式^[2].为此,我们开展了玉米整秸覆盖免耕条件下黄土高原旱地养分消长积累及增产效应的研究。

Abstract:金属材料在土壤中的腐蚀状况与土壤性质有明显的关系^[1]。从已有的结果来看,金属管道的腐蚀程度、穿孔数量主要与土壤的电阻率、含盐量有关,如北方苏打盐土和滨海盐土就是如此^[2]。而对于南方酸性土壤或淹水还原性强的土壤则有所不同,因此,不能不考虑另外的腐蚀因素,如pH和Eh的影响,这两个因素虽已被能源部列为土壤腐蚀性指标之一^[3],但由于过去这方面缺乏较为严格的对比实验,指标定得比较粗略,因此,本工作就这方面做一点探讨,同时也借此探索并评价金属材料腐蚀状况的土壤化学方法。