Physical And Chemical Properties Of Several Agriculture Waste Compost Substrates And Utilization In Landscape Mulch And Culture

More and more restrictions have being imposed on peat use due to greatly-reduced peat resources and wetland conservation, the peat substitute studies have become hot research project worldwidely in recent years. Foreign scholars use municipal solid waste compost, bark, wood fibres, etc. as peat substitute according to various national condition, and properties of peat substitute were studied. In our country, agriculture by-product resources are excessive and badly wasted and resulted in environment problems. The substrates cost can be greatly reduced if use agriculture by-product resources as peat substitute, so it is important to study it. Moreover, in our country, the theory studies of growing media is relative lagged behind, and the current researches of growing media are simple media formulations and effect of growing media on plants growth, it is necessary to conduct a deep research to properties of growing media, if we know clearly of the properties of growing media, we can have clear objectives when we mix and manage growing media. The research is to deal with agriculture waste by composting process, and use the international research methods of growing media, also learn research methods from soil science, to deep study physicochemical properties of agriculture waste compost substrates and improve it, which may provide the theory and the technical support for its proper usage as peat substitute in the soilless horticulture, and to research their utilization in landscape mulch and culture.1. At the beginning of the composting process, the temperature of each material rapidly elevated and lasted for a while, followed by a quick drop, the speed of temperature rise and the maximum temperature differ from material to material.Turn piles may enhance the compost temperature. Corn straw don't need to add water in the entire compost process. Wheat straw is very difficult to absorb water before composting, but after short composting time, its water-absorptivity boost up greatly. The cotton straw dehydrate quickly, it needs to add water unceasingly in the composting process. Bean straw and spent mushroom compost only need to water in the earlier period. In the composting process, each kind of materials tends to increase water-holding pores. For corn straw, wheat straw and bean straw, changes tendency of their pH value present decline first, then elevate, and decline again subsequently. pH value of cotton straw and spent mushroom compost elevate first and then decline, yet two curves are different. The changes tendency of each material's electric conductivity (EC value) present elevate first, then reduce. When it comes to anti-decomposed ability, spent mushroom compost is strongest, dicotyledonous plant straw has stronger anti-broken ability than monocotyledonous plant straw,and volume and weight reduction of the latter is more than the former in the composting process. Bulk densitys of materials increased at the different degree along with composting process. Each material's NH4+ N and total N elevated at the earlier period, then reduced at later period, and the C/N ratio (C/N) of all materials showed a downward trend. Germination Indexes(GI) of various substrates increased rapidly after different composting period, and GI close to or exceed 100% in later stage.2. Bulk densities of corn straw and wheat straw substrates are smaller, and they have more air pores, and bulk densities of cotton straw and bean straw substrates are bigger, and have more water-holding pores. Corn straw and wheat straw substrates have more available water (EAW) and less buffer capacity(BC) than cotton straw and bean straw substrates. Maximal moisture absorption and water content under the same pressure increase along with the particle size increased as by weight water content expression, and they reduce along with the particle size increased as by volume water content expression. Initial moisture contents of corn straw and wheat straw substrates are lower, and their evaporation rates are faster in the early period,but initial moisture contents of cotton straw and bean straw substrates are higher, and their water retention abilities are stronger. Evaporation rate of straw substrates can not be reduced by adding super absorbent polymer, but can increase their container capacity and everyday moisture content in the evaporation process. The rising heighte of capillary water of four kinds of straw substrates have smaller differences, and the velocity of capillary water upward movement speeds up as the particle size reduced. permeability coefficientes of corn straw and wheat straw substrates are 74.81 mm·s-1 and 99.09 mm·s-1, but permeability coefficientes of cotton straw and bean straw substrates are 22.82 mm·s-1 and 23.50 mm·s-1, and the effect of particle size variation on permeability coefficient is strong, vermiculite can reduce permeability coefficient of each straw substrate, however, wheat straw and corn straw substrates was greater affected than cotton straw and bean straw substrates. With the substrate decomposition, the permeability coefficient will decline at different levels.3. pH values of wheat straw, corn straw, bean straw and cotton straw substrate are 6.12, 6.58, 7.64 and 7.42, only pH value of wheat straw substrate is in the ideal range between 5.5 to 6.5, corn straw substrate is slightly higher, bean straw and cotton straw substrates are significantly higher. The pH value can be reduced by adding sulfur powder in the composting process, but the electrical conductivity (EC value ) of substates also increased significantly. As the pH value and electronic conductivity(EC) value of peat are low, pH value and EC value of the straw substrate can be obviously lowered by mixed with peat. pH value can also be lowed by using dilute sulfuric acid, yet the pH value can increase at a faster rate along with increasing water times. FeSO4·7H2O can also cause the pH value of straw substrate to lower, but bean and the cotton straw substrate need a lot of FeSO4·7H2O. EC values of straw substrates all reach ideal range(<2ms/cm)after washed two times. EC value spatial distribution of each straw substrate is different significantly in the less moisture situation. There are more initial nutrients in the straw substrates, and washing can reduce macro-element contents, but effect of washing on middle and trace element contents is not significant. CEC of corn straw and wheat straw by weight expression are higher, but CEC of wheat straw by volume expression is the lowest. The effect of different particle size on CEC of straw substrates depend on by weight expression or by volume expression. The anti-leaching ability of wheat straw substrate is weak, more nutrient was leached out, but the anti-leaching ability of the other three straw substrates is stronger. The leaching nutrients of bean and cotton straw substrate are few relatively in the earlier period, and more in the later period.4. To study the feasibility of spent mushroom compost and peat substitute, the physical and chemical properties of the peat and spent mushroom compost were compared, and growth barrier factors of spent mushroom compost were analyzed and adjusted. The results indicate that spent mushroom compost has more larger-size particles, more air pores, better permeability, less water-holding pores than peat. So it need less water volume and more times, but it's water losing rate is lower than that of peat. The velocity of capillary water upward movement of spent mushroom compost is higher than peat, and the effect of wetting agent on spent mushroom compost is not significant. Spent mushroom compost has similar moisture retention curves with peat. The nutrient retention property of spent mushroom compost is lower than that of peat, so the frequency of fertilization need to be increased. Electronic conductivity value of spent mushroom compost is high, but the one of peat is low, so the EC value of the former can be adjusted by mixing with peat in proper proportion or washing with water. pH value of spent mushroom compost is high, but it can be lowered by adding sulfur powder as well as dilute sulfuric acid or mixing with peat.5. Landscape mulch of agricultural waste compost may reduce the soil bulk density, increase the soil porosity, enhance the soil permeability coefficient, reduce evaporation, reduce soil and water loss. When landscape mulch of agricultural waste compost is used, ground temperature variation in one day become gentle, varying of temperature significantly reduced, and annual variation of temperature significantly reduced too, spring soil warming is slowing down. Weeds control effect of landscape mulch of agricultural waste compost is ideal, if mulch thickness is suitable, weeds can be completely inhibited. Landscape mulch of agricultural waste compost can raise the soil organic matter and nutrients obviously, but it lie on different materials and different thickness. Corn straw and wheat straw and bean straw decomposed faster, and wheat straw decomposed fastest, cotton straw and spent mushroom compost decomposed slowly, especially for spent mushroom compost. Mulch of agricultural waste compost can promote the growth of landscape plants.6. Substrates of agriculture resource waste compost can greatly promote the growth of garden plants compared with the traditional soil cultivation. Seeds germination rate can be increased if substrates of agriculture resource waste compost were washed, or reduced particle size with screen, and mixed with peat and other measures. Most of substrates of agriculture resource waste compost mixed with peat can make up their deficiency by acquiring strong points of peat, and promote the growth of plants.