Digestion Of Rice And Wheat Straws By Earthworms And Use Values Of Earthworm Casts

Crop stalks are not only agronomic organic solid wastes, but also important resources for comprehensive utilization, such as organic fertilizers, feedstuff, fuel and industrial materials. With the rapid development of Chinese agriculture and the great change of rural energy structures, the excess crop stalks is becoming a serious problem. Safe treatments of crop stalks is helpful to the decrease of environmental pollution and to the agricultural sustainable development.The earthworms can convert agronomic organic solid wastes to casts, which is good organic fertilizers for various crops.The earthworms were used in this experiment to decompose the straws of wheat and rice. For wheat straws five treatments were carried out: 1) straw heap was inoculated with 4kg earthworms and intermingled with sludge layer; 2) inoculated with 2kg earthworms and also intermingled with sludge layer; 3) inoculated with 4kg earthworms and no sludge layer existed; 4) inoculated with 2kg earthworms and no sludge layer existed; 5) inoculated with no earthworms and no sludge layer existed (as the control).The experimental treatments of rice straws included: 1) straw heap was inoculated with 6kg earthworms and straw maintained integrated; 2) inoculated with 6kg earthworms and straw were pulverized; 3) inoculated with 4kg earthworms and straw maintained integrated; 4) inoculated with 2kg earthworms and straw maintained integrated; 5) inoculated with no earthworms (as the control). After 60 days of decomposition, amount of earthworms, casts and unrotten straws were measured, and total N, P, K in earthworm casts and mixture of straw and earthworm casts, organic material content in casts were also analyzed.Pot experiments were used to study the effects of earthworm casts on the vegetable growth. Five treatments were designed: 1) 0 kg casts + 1 kg soil and no casts; 2) 0.25 kg casts + 0.75 kg soil; 3) 0.5 kg casts + 0.5 kg soil; 4) 0.75 kg casts + 0.25 kg soil; 5)1 kg casts + 0 kg soil. 20 day old seedlings were sampled to measure plant height, stem diameter, stem height, soluble sugar content in green vegetable, contents of soluble solid and nitrate in green vegetable and amaranth. The results indicated that:(1) Total N, P, K content in straws decreased with the compost treatment;(2) Total N, P content in the mixture of residual wheat straw and earthworm casts increased with the digestion of earthworms. With the same amount of earthworm inoculation, total N, P content in the mixture with sludge layer was higher than that without sludge layer. Total N, P content in the mixture with less earthworms was higher than that with more earthworms.(3) Earthworm casts with wheat straw decomposition has higher total N, P content when sludge layer existed, compared with the treatment of no sludge layer. Total K contend just exhibited the contrary tendency.(4) Compared with the treatment of no sludge layer, organic materials content was higher when sludge layer existed.(5) Appropriate earthworm casts were helpful to the growth of green vegetable and amaranth. When the ration of casts and soil was 1:1, the germination rate reached highest. Plant height, stem height and stem diameter of two vegetables increased first and then decreased with the increase of cast/soil ratio, and reached the highest at 1:1. The tendency not only existed in the seedling stage, but also in the harvest stage.(6) Soluble sugar content in green vegetables reaches highest when cast/soil ratio was 3:1. Soluble solid content in two experimental vegetables increased first and then decreased with the increase of cast/soil ratio, and reached highest at 1:1. Nitrate content in two vegetables increased with the increase of cast/soil ratio.