The Feasibility Of Organic Mineral Resources Of Shaanxi Applied In Agriculture

Peat, oil shale and grass charcoal are the rich organic mineral resources in Shaanxi. They are mainly distributed in Weibei Region of the following cities: Tongchuan, Xianyang, Weinan and Yan'an and the arid and ecologically fragile parts in Yulin. They have rich reserves and highly workable extent. Although people have realized the importance of the application of the three resources in agriculture, they have difficulties in exploring these resources owing to their different properties which results from the different carbon-forming plants and the environment conditions. The primary problem in exploring and applying these resources is to know their physical and chemical properties, and then evaluate their value in application, locate the facets and fields of their application, carry out scientific projects in application. The research materials on the properties and the value of application in agriculture of these resources in Shaanxi are still insufficient and unsystematic, lack of scientific evidence of application in agriculture.This paper contributes to solving these existing problems. In the paper, the author makes a systematic testing and analysis of the peat resources in Bin County, the oil shale resources in Tongchuan and the grass charcoal resources in Yulin from the perspectives of composition and content of organic matter, mineral nutrient content, salt components and content, water holding capacity and the content of heavy metals in the three mineral resources. Through this systematic analysis, the author attempts to probe into the problems existing in the application of the three resources in agriculture, offer some measures for improvement and evaluate their value in application. The following are the five major findings:I. The content and composition of organic matter in the three resources differ greatly. The content of humin is the highest, fulvic acid is higher. Grass charcoal has a high content of humic acid and exploration value in industrial extraction and production of new fertilizer additive agent. The three resources have promising prospects as cultural substrate disposition. And it is necessary to carry out sterilization treatment beforehand. The high content of asphalt restricts the safe use of these resources. Their safe use can be ensured under the condition of physical volatility processing or biodegradation processing.All of the three resources contain rich organic matter. The content of organic carbon in peat, oil shale and grass charcoal is 57.83g/kg,117.19g/kg and 272.32g/kg, respectively, which far exceeds that in the soil. And this is one of the conspicuous features of their application in agriculture. The content of humic acid is also rich, which takes up 8.67g/kg,19.84g/kg and 156.86g/kg, respectively, and it is helpful for plant growth. The content of organic matter and maize biomass in the three resources go in the following order from high to low: grass charcoal--oil shale--peat.II. The feature of available nutrient content in the three resources is that available nitrogen is high, available potassium is all right, while available phosphorus is insufficient. The feature of total nutrient content is that total nitrogen and total phosphorus are high, total potassium is insufficient and its supply capacity is rather low. In agricultural application, it is urgent to replenish phosphorus and a long run to replenish potassium.The content of total nitrogen (4.26-12.74g/kg), total phosphorus (1.05-2.59g/kg) and available nitrogen (279-783mg/kg) are high in the three resources, living up to the first grade of evaluation criteria for soil nutrient in the Second National Soil Census. The content of available phosphorus (14.51-21.58mg/kg) and available potassium (144-380mg/kg) are medium in the three resources, living up to the second or third grade of evaluation criteria for soil nutrient in the Second National Soil Census. The content of total potassium (1.07-2.82g/kg) is relatively low, living up to the sixth grade of evaluation criteria for soil nutrient in the Second National Soil Census. The proportion of nitrogen, phosphorus and potassium is imbalanced. Compared with Lou soil in Guanzhong, the proportion of total nitrogen and total phosphorus are relatively high, while the proportion of total nitrogen and total potassium, available nitrogen and available potassium are very high. The content of total nutrient and available nutrient in the three resources go in the following order from high to low: grass charcoal--oil shale--peat. In general, the content of nitrogen is sufficient, while phosphorus and potassium are insufficient in the three resources.III. Total water-soluble salt in the three resources is rather high, especially SO₄^2- in salty ions is very high. This has become one of the interruptive factors of their being used in agriculture. It is necessary to remove salt beforehand and at the same time a proper amount of lime is needed.CEC is high in peat, oil shale and grass charcoal, which takes up 36.22cmol/kg, 39.37cmol/kg and 87.86cmol/kg, respectively. Total water-soluble salt is too high, which takes up 11.02g/kg, 8.27g/kg and 19.30g/kg, respectively, and this is one of the interruptive factors of their being applied in agriculture. Total water- soluble salt is too high in grass charcoal, especially SO₄^2-(4.041g/kg), thus seriously influencing the normal growth of plant roots. CEC in the three resources goes in the following order from low to high: peat--oil shale--grass charcoal. Total water-soluble salt goes in the following order from low to high: oil shale--peat--grass charcoal.IV. Water holding capacity of the three resources is all right, higher than that of the soil. Water holding capacity is high, whereas wilting coefficient is rather high owing to the high content of salt.Water holding capacity of peat, oil shale and grass charcoal are higher than the soil. The content of maximum available water is 25.74%, 24.50% and 36.07%, respectively, which goes in the following order from high to low: grass charcoal--oil shale--peat, and they all demonstrate positive correlation with biomass.V. The content of As in the three resources seriously exceeds the limit standard. The pollution problem resulting from heavy metals in grass charcoal is very severe, seriously threatening food security. Therefore, it is advised that grass charcoal be used as a material to extract hunics acid, not cultural substrate.The content of As in peat, oil shale and grass charcoal is 61.90mg/kg, 58.15mg/kg and 74.75mg/kg, respectively, exceeding the limit standard (40mg/kg) for non-environmental damage agricultural products. Cd (1.49mg/kg) and Hg (9.209mg/kg) also exceed the limit standard (1.0mg/kg and 1.5mg/kg) for non-environmental damage agricultural products. In order to apply the three resources, especially grass charcoal, it is very important to solve the problem of too much heavy metal.