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Study on Water and Fertilizer Retention Properties of Bentonite-mushroom Residue Composite Material

Author: YaoZuo
Tutor: DengLiangJi
School: Sichuan Agricultural University
Course: Soil
Keywords: bentonite mushroom residue drought relief and fertilizer conservation substrate cultivation
CLC: S482.99
Type: Master's thesis
Year: 2013
Downloads: 52
Quote: 0
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The sustainable development of agriculture in China is restricted by water and nutrient deficiency. Products used to retain water and nutrients in farmland came into being. However, those macromolecule products have problems such as high cost, poor salt tolerance and potential secondary pollution. On the other hand, China is rich in bentonite and mushroom residue with excellent physical and chemical properties, which played an important role in improving soil structure and fertilizing the soil.The study is based on the characteristics of bentonite and mushroom residue, such as water absorption, adsorption, adhesion and pority, nutrient-rich. We made bentonite-mushroom residue composite material according to the proportion in quality in which bentonite:mushroom residue1:1,1:1.5,1:2,1:2.5. Through the indoor simulation and pot experiment, we compared and analyzed water and fertilizer capacity comprehensively in sandy soil, loam soil and composite materials. We also studied its effects on two crops of cabbage and peppers, to explore the best ratio. The results showed that:(1) Bentonite have high CEC, high base saturation and good capacity in nutrient preserving and fertility. But it also have low content in nitrogen, phosphorus, potassium and organic matter, heavy clay texture. pH is alkaline. So it shouldn’t be used directly. Mushroom residue have neutral pH, high nutrient content, loose texture and aggregate structure similar with soil. But also shortcomings like poor water-stable, poor roots fixed and high salt content which made it inappropriate to be used alone as a culture substrate.(2) Bentonite-mushroom residue composite material can overcome the shortcomings of the two to achieve mutual complementarity. Composite material’s pH7.5-7.8, bulk density0.29-0.47g/cm3, total porosity is greater than75%, aeration porosity15.1-18.4%, water retention porosity58.0-62.5%, CEC40.06-45.03cmol/kg, EC is less than2.5mg/cm3. T3and T4treatment are better than T1and T2, for its’pH is closer to neutral, and have better porosity and physical and chemical properties.(3) Composite material play a good water-holding role in water conservation through absorbing a great deal of water and reducing water evaporation rate. Water retentivity T1>T2>T3>T4>CK2>CK1. T1-T4absorbent multiples are up to3.60-3.97, which is about 3times than sand,2times than loam. It increased with the proportion of bentonite, but the difference was not significant with each other. In inadequate suction condition, composite material decreased water evaporation rate than the sandy soil, but the difference with the loam is very small. So it is difficult to fully display its role in water conservation. However, in sufficient absorbent condition, composite material could maintain a high water content for a long time.(4) Composite material have good nutrient regulate and control ability. N total leakage decreased by38.18-51.50%compared with CK1, decreased by30.57-45.53%compared with CK2. N conservation effect T1>T2>T3>T4. K total leakage decreased by20.02-27.89%compared with CK1, decreased by14.05-22.51%compared with CK2. K conservation effect T1>T2>T3>T4. But for P which was not easy to migrate with water, the total leakage of T1-T4ware higher than CK2but less than CK1. Composite material promoted the release of P, but also increases the possibility of P leaching losses. It also reduced the volume of leachate significantly, which played an important role in the reduction of nutrient loss.(5) Composite material could meet plant requirements and is suitable for plant growth. Cabbage seed germination rate increased by12.5-17.5percentage point than CK1,25.0-30.0percentage point compared with CK2. Survival time under drought conditions extended11.3-23.3d. T2has longest survival time, followed by T1,T3.It promoted chili vegetative growth. Pepper yield increased by75.83-191.09%than CK1,5.91%-75.34%compared with CK2. Yield and biomass of T3and T4ware higher than T1,T2, but the difference was not significant. Because of the strong adsorption to nutrient ions of bentonite, the availability of nutrients was reduced at early stage, resulting in lack of nutrient supply in the short term. Early growth of plant was affected, particularly short growing season crop like cabbage which application was ineffective, even cut down in yield.(6) Considering factors including basic physical and chemical properties, water and fertility conserving ability, effect on plants as well as costs, draw:T3treatment, namely bentonite:mushroom residue mass ratio1:2was optimal.

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