Abstract:Sustainable agriculture is a way of thinking or a target for the establishment of a farming system which is sustainable for protection of resources and environment for it's economic success and for social satisfaction. For the long-term goals, the only way out for Chinese agriculture is to establish and to develop the sustainable agriculture. However, the changes of Chinese agriculture in recent years implied that it was far from the sustainable aims. The healthy development of agriculture in China needs not only the stimulation from market mechanism but also, more important, the government guidance and the advancement of agriculturel sciences. One of the tasks facing soil science is to develop the theory and practice in land reclamation, soil managerrient and to establish the relevant techniques for the sustainable development of agriculture.

Abstract:The present paper deals with a study on redoxic features of calcareous purple soils after waterlogging through a simulated incubation test. The results show that (1)as compared with haplie purple soils and dystric purple soils, calcareous purple soils were difficult to develop strong reduction status, which was related to the contents of CaCO₃ and active iron of soils (2) the different organic substances had different influences on soil reduction intensity and (3) the intensity factor (redox potential) was highly correlated with the amount factor (content of reducing materials) and was consistent with the growth status of rice. When Eh<-100mV and the total amount of reducing substances>3.63cmol/kg, soils were easy to develop strong reduction ststus, which would poison the rice growine.

Abstract:Under the condition of urea fertilization, the hydroquinone (HQ), as a urease inhibitor, was applied to postpond the hydrolysis of urea for decreasing the volatilization of ammonia and restraining its nitrification. As a protective measure of urea fertilization, HQ was very effective in alleviating the inhibition effect of urea fertilizer on the symbiotic nitrogen fixation System of soybean. HQ was found to have no unfavourable effect on the growing of the purecultured soybean rhizobia, the growing of the seedings of soybean and primary forming of the nodules at an applied levels of HQ. Furthermore, the respiratory activity of isolated-cultured active root nodule and the activity of succinic dehydrogenase were promoted remarkably. Under pot and field conditions, fertilizing urea with HQ, compared with check (no HQ), could notably raise the nodule quantity and increase the total nitrogen fixation activity of single plant and enhance the content and relative abundance of ureide nitrogen in plant hadromestome of soybean. Therefore, fertilizing urea with HQ could improve the development of the soybean symbiotic nitrosen fixation system and coordinate the supply of the nitrogen sourced from nodule or soil (fertilizer) needed by soybean. Thereby, the rich nitrogen could be provided for synthesizing protein of seed. For this reason, fertilizing urea with HQ could increase soybean yield very remarkably.

Abstract:Based on pot-experiments with ¹⁴C-hydroquinone and ¹⁵N-urea, the distribution, forms and transfer of hydroquinone (HQ) in a soil-rice system were discussed. Residues of hydroquinone in soil increased with the soil depth, with an average of 0.041mg/kg. 13% of hydroquinone was decomposed as CO₂ and H₂O due to biochemical and physiochemical actions. 49% of the residue-¹⁴C entered into high moleeular compounds and could not be extracted by solvents, while 45% into low molecular compound. Metabolism, distribution and absorption of hydroquinone in rice were determined. The contents of hydroquinone in brown rice and stem (and leaf) were 0.07mg/kg and 0.05mg/kg respectively. Results of pot-experiment show that exogenous hydroquinone participated in metabolism of C in rice and promoted the utilization of urea-N in soil. Limiting value of hydroquinone residual in soil after long-term application of slow-release urea was calculated to be 0.044 mg/kg, which was far lower than the hydroquinone standard 0.20mg/kg soil for human health in U.S.A. It could be concluded that long-term application of slowreleasing urea is very safe.

Abstract:Pot experiments were conducted to study the effects of boron on floral organs development and seed-setting of rapeseed (Brassica napus L.).The results are as follows: In boron-free (B₀) and boron-normal (B₁) plants, boron concentrations of floral organs were greater than those of leaves, especially with boron in pistil and stamen twice as high as that in leaves. But leaves had the greatest boron concentration when boron was excess (B₂). Boron deficiency led in reduction of the length and weight of stamen and in abnormality of anther tapetum development. Differentiation of pollen sac was inhibited. It was found that both boron deficiency and excess reduced the numbers of effective siliques per plant and seeds per silique, rate of siliques, rate of seed-setting, and rape seed yield. The effect of boron on the number of ovules per silique was not significant. Compared with Ningyou No.7 (a high erucic acid type), Ningyou No. 8 (a low erucic acid type) was more sensitive to boron-deficiency and boron-excess.

Abstract:Factors related to the content of available Mo in soils of Anhui Province were investigated. Soils derived from siliceous shale and lacustrine sediments had the highest available Mo content, averaging 0.176 and 0.157 μg/g respectively; soils from the inundated deposits of the Yellow River, loess fossil lake deposits and purple sand stones had the lowest available Mo content, averaging 0.005-0.070 μg/g, with 90% of the soils below the critical value of 0.150μg/g soil. Available Mo content of 140 paddy soils were about 0.150 μg/g, but those of 81 upland soils below 0.100μg/g. Variation of 1Vjp content were found among various paddy soil types. Gleyed paddy soils contained apparently more available Mo than other paddy soils. The effect of P addition on soil available Mo content varied with the P rate, soil type, time, and cropping system. The shortage of soil available Mo due to long-term cropping was a serious problem in the agricultural production of Anhui Province, though it could be partly supplemented by returning crop residue to the fields. Extra fertilization of Mo is needed.

Abstract:According to the results of an eight-year study, the effects of soil region, the distribution of zonal soil type and pH, carbonate and organic matter on regional differentiation of critial concentrations and environmental capacities of Cd,Pb,Cu and As in soils are analysed, and the pH value of soil and the distribution of soil type are concidered as the main influenting factors. there was a negative correlation between the critical levels and environmental capacities of Cd and Cu in soils and the pH of soils. The critical levels and environmental capacities of Cd and Cu in soils decreased with the distribution of soil types from south to north. The critical levels and environmental capacities of As in soils increased with the soil pH and the distribution of soil types from south to north, but there was no correlation between them.

Abstract:In the semi-arid and soil erosion region of western Liaoning, we should develop forests to conserve water and soil above all so as to prevent soil erosion and recover soil fertility. In contrast to the pure forest the Chinese pine mixed forest had obvious superiority in improving physical and chemical as well as antierosion properties of the soils. The mixed forest of Chinese pine and broadleaf trees (including shrubs) could increase soil wetness by 10-30% and humus content by 7-76.4% and decrease the volume weight of the soil by 10%.In addition, the mixed forest of Chinese pine and broadleaf trees could raise the water-stable soil aggregate by 22.2-124.4% and reduce the soil erosion rate by 6.6-26.3%. In this area the suitable species to be used as the mixed trees should include Acer trumcatum, Quercus m ongolica, Caraaana microphylla etc.

Abstract:Based on analyzed results of major elements of 181 samples from 34 profiles and trace elements of 176 samples from 36 profiles, this paper discusses soil geochemical forming processes and the spatial differentiation of major elements and trace elements such as Zn, Cu, Ni, Co and V in soils of the Tianshan Mountains and their neighboring regions. During formation of the soils there are three main geochemical processes which are Ca and Na-leaching process, Mg and Ca-enrichment process and Na-enrich-went process. Spatial differentiation of the elements was from the leaching of Ca, Na and Mg in high mountain to the precipitating of salts of Ca, Mg and Na，respectively, according to the increasing of their solubility and gradual decrease of the total content of trace elements from high mountain to basins with lowering of altitude, decreasing of moisture, and increasing of temperature.

Abstract:The vertical distribution of salt in the soil profile in the salt-affected areas of the Huang-Huai-Hai Plain is characterized by intensive salt accumulation at the soil surface and its rapid changes with seasons. To regulate salt distribution in the soil profile, an additional fraction of irrigation water, other than leaching specially, would let crops stand to survice. The additional amount of water is called Irrigation Leaching Requirement (ILR). By soil column experiments and numerical procedure, a method to ascertain the minimum amount of ILR is discussed, Results of ILR under different salt conditions are given. Based on salt tolerance of crop, ILR changed from 191 to 1350 m³/ha at seedling stage, and from 690 to 3950 m³/ha in growing period. The paper provides an approach to reclamating salt-affected soil and making efficient use of water resources.

Abstract:From the continuation of pore distribution, the uncertainty in quantity for the wettness of the capillary moisture bound disruption and the classification of soil water moving stages is discussed. According to the measured data of the moisture thermodynamic functions in the soil-plant-atmosphere continuum, we identified the limitation of the principle of entropy increasing and the suitability of the principle of partial molar gibbs free energy decreasing when judging the direction of soil water movement. Moreover, a further interpretation is made on three basic points of the second law of water flow and the misunderstanding when using the law.

Abstract:The thermal analyses (DTA and TG) of various organo-mineral complexes is seven soil types of Tibet were carried out based on the fractionation and assessment of soil organic matter. The results show that the degree of organo-mineral completation in the test soils was lower. The loosely combined carbon and tightly combined carbon occupied a relatively dominant position in total completed carbon. Exothermic peaks were found at about 310℃ and 430℃ for original soil samples and its various organo-mineral completes. Another etothermic peak at 510℃ existed in a few soil samples in the study. An obvious，weight loss followed each etothermic peak. From the results of the thermal analyses (DTA and TG) and the fractionation and assessment of organic matter in the soils discussed, it can be concluded that the heavy fraction of organic matter stably and tightly combined with soil mineral particles was the dominant factor of the etothermic peak at 310℃, the loosely combined organic matter was pyrolyzed at about 430℃, and the light fraction of organic matter which did not complex with soil minerals was pyrolyzed at about 510℃. The results also indicated that the pyrolytic enthalpy changes (ΔH) of organic matter in the alpine steppe soil and subalpine steppe soil were greater than those in the alpine meadoav soil and subalpine meadow soil respectively.