Studies On The Preliminary Treatment Of Cotton Straw Composting As Soilless Culture Substrate And Effect On The Cucumber Growth

Eco-organic soilless culture has been the main type of soilless culture, so farmers need more andmore substrate. The research on how to change cotton straw into soilless culture substrate throughcomposting is not only a solution of recycling organic waste but also a reduction of cost for soillessculture, which has a certain theoretical value and practical significance. Cotton straw size,carbon-nitrogen ratio and nitrogen source were investigated to find out the effects on the process ofcotton straw composting by using the orthogonal design method. The parameters included compostingtemperature、C/N ratio、bulk density、 pH、 EC、accumulated temperature、water holding capacityand air filled porosity etc. The aim was to find the better condition of cotton straw composting asSoilless Culture Substrate through the parameters. According to the result, cotton straw after15days、30days、45days、60days composting and peat were mixed with cinder to be four treatments D15、D30、D45、D60and CK（V/V=1：1）. Study the effect on the growth of cucumber plants to determine thephysicochemical properties of the suitable composting of cotton straws. The main results are as follows:1. The Favorable Condition of Cotton Straw Composting as Soilless Culture Substrate was25:1ofC/N ratio,1cm of cotton straw and mixture of chicken manure and urea as added nitrogen source. Itindicated that during the composting period,25:1of C/N ratio,1cm of cotton straw and mixture ofchicken manure and urea as added nitrogen source were a favorite condition to keep the hightemperature(＞50℃) of pile of cotton straw, and it was up to9days、10days、8days respectively. C/Nratio had significant influence on total porosity reduction, and the highest record (66.0%) occurred inC/N of25:1. Cotton straw size had significant influence on water holding capacity、accumulatedtemperature and bulk density increase, and the highest record (59.2%、1315.75℃、0.30g/cm~3) occurredin Cotton straw size of1cm. Nitrogen source（chicken manure and urea）had significant influence onaccumulated temperature, and the highest record (1354.41℃) occurred in Nitrogen source of mixture ofchicken manure and urea. It increased by7.6%and9.2%respectively, compared with urea and chickenmanure added separately.2. Physical and chemical parameters of cotton straw of different composting time(15day、30day、45day、60day) had significant difference and relativity. Water holding capacity、EC and bulk densitywere positively correlated with each other and increased as composting time expanded. Air filledporosity and pH were positively correlated with each other and decreased as composting time expanded.Air filled porosity、pH and EC of cotton straw with different composting time had significant difference.Bulk density and of cotton straw in30、45、60days’composting had significant difference. Waterholding capacity of cotton straw in30、45、60days’composting had no significant difference.3. Physical and chemical parameters of cotton straw of different composting time mixed withcinder had significant difference with CK. The result of principal component analysis showed thatwater-holding porosity、pH、 air filled porosity/water holding capacity ratio、bulk density, air filledporosity of substrate had great influence on cucumber growth. Before cultivating cucumber, waterholding capacity、 bulk density air filled porosity and air filled porosity/water holding capacity ratio ofCK were56.36%、0.58g/cm~3、6.42%、0.11respectively. Water porosity and bulk density of D15were significantly lower than that in CK about25%,21%respectively, and air filled porosity and air filledporosity/water holding capacity ratio were significantly higher than that in CK about117%,191%respectively. Water porosity and bulk density of D30were significantly lower than that in CK about26%,21%respectively, and air filled porosity and air filled porosity/water holding capacity ratio weresignificantly higher than that in CK about82%,154%respectively.4. Physical and chemical properties of the cotton straw of composting from15days to30days weresuitable for cultivating cucumber. it could be used as substrate to cultivate cucumber when physical andchemical parameters of cotton straw composting were up to water holding capacity(40-55%)、air filledporosity (33-22%)、bulk density（0.23-0.24g/cm~3）. The yield of single plant of D15(707.63g) wassignificantly higher than other treatments and CK, followed by D30(620.79g) and four treatments weresignificantly higher than those of CK about51%、32%、15%、8%respectively.