The Coupling Effect Of Soil Water Content And PH On The Switchgrass And Their Optimization

Switchgrass(Panicum virgatum L.), a perennial grass, which can be planted in marginal lands to avoid competition with food crops, has emerged as an ideal candidate for bioethanol production. The soil of marginal lands is poor, high salt and alkali, water deficiency. To introduce switchgrass to the northwest of our country, to be energy grass and plant for revegetation and water conservation, to plant in large area successfully, determining the optimal soil water content and pH value for bioethanol production using switchgrass is urgent. Therefore, using the vegetative period switchgrass Alamo as experimental material, the experiments were designed to incorporate two factors at five levels using orthogonal matrix, a total of 22 treatments, 3 replicates per treatment. The soil water content(X1) had five levels: 8%, 16%, 20%, 24%, and 32%; pH(X2) had five levels: 4.9, 6.3, 7.0, 7.7, and 9.1. After 7 weeks’ treatment, we cut it to evaluate yield indice(fresh weight, dry weight,shoot length and No. of tillers), quality indice(acid detergent fiber, neutral detergent fiber, acid detergent lignin, cellulose, hemi-cellulose, and lignin) and physiological indice(soluble sugar content, proline content, MDA content, chlorophyll content and relative conductivity) in Alamo switchgrass.The results of our experiment were as follows:1) The effect of soil water content and pH on the dry mass yield of switchgrass was synergistic. The adverse effect of acid on the No. of tillers of switchgrass was more than alkali.2) Cellulose content and acid detergent cellulose content of switchgrass reached their maxima and acid detergent lignin content reached its minimum when soil water content was 20%, which was not significantly different with the condition when soil water content were 24% and 32%.3) The soluble sugar, proline, MDA content and relative conductivity of switchgrass reached its maximum under extreme water deficiency, which was significantly different with other treatments.4) Soil water content and pH stress yielded a significant coupling effect fresh mass, No. of tillers, neutral detergent fiber content and proline content of switchgrass.5) By model operation, the optimization result is the optimal condition for biomass production of switchgrass was soil water content =32.0% to 44.4% and pH=6.3 to 8.1.6) There was a significant and positive correlation between the cellulose content and dry mass, fresh mass, acid detergent fiber content, neutral detergent cellulose content, shoot length, No. of tillers, and a significant and negative correlation between the cellulose content and acid detergent lignin content, hemi-cellulose content, soluble content, proline content, MDA content and relative conductivity.