| Sichuan is a major rapeseed planting province,with a rapeseed planting area of 19 million mu.With the improvement of agricultural mechanization,the direct return of rapeseed straw to the field has become the main way of straw recycling.The treatment measures of rapeseed straw returning to the field not only avoid the harm to the environment caused by straw burning,but also return the nutrients in the straw to the farmland soil,increase the nutrient recovery and utilization rate,and save the cost of agricultural production.However,with the practice of rapeseed straw returning to the field in agricultural production,the different ways and quantities of returning to farmland in different places resulted in different effects on the growth of later cropping rice.Therefore,it is very important to study the suitable method and quantity of rapeseed straw returning to the field and the new way of straw returning to the field for the production of rice.In this paper,we designed three experiments,including(1)the effects of straw returning method and amount on rice growth(2)the nutrient effects of straw returning to the field(3)the preliminary exploratory experiment of new slow-release fertilizer,to study the effect of rapeseed straw returning to the field on rice growth and nutrient effect after the straw returning to the field,as well as other possible utilization ways of rapeseed straw returning to the field.And the main conclusions of this study are as follows:(1)Regardless of straw mulching or incorporation,straw returning inhibited the growth of aboveground parts and roots in the early stage of rice growth,and the inhibitory effect on rice growth increased with the increase of the amount of straw returning.Different returning methods had significant effects on plant height,tiller number and fresh weight of rice,while the returning quantity had significant effects on tiller number and fresh weight.In addition,the interaction of straw returning method and amount had the significant effect on the white root of rice after transplanting.(2)In mulching conditions,the early stage of the rice transplanting,rape straw returned amount under 6.0t/hm~2 when no significant impact on rice growth,but continue to increase the quantity can inhibitory the growth of rice root system.In the later stage of the rice transplanting(36-65d),the growth of total root was weaker than control,and the fresh weight of root decreased with the increase of returning amount.In incorporation conditions,the effect of straw incorporation on rice root growth in the early stage was the same as that of straw mulching,but it was beneficial to the improvement of root activity in the later period of straw returning.Under different straw returning treatments in the early mulching stage,the root length and fresh weight of rice in the same soil layer were significantly different(P<0.05),the low returning amount(FG1,FG2)could promote the root growth in the upper layer(0-30cm)and inhibit the root growth in the deep layer(30-50cm),and the excessive returning amount(FG3)had adverse effects on the root growth in different soil layers.In the later stage of transplanting(36-65 d),the appropriate amount of straw returned to the field promoted the growth of roots in the deeper soil layer(10-50cm).Straw incorporation treatment is not conducive to the root growth of in each soil layer in the early stage of transplanting,and the inhibitory effect increases with the increase in the amount of returning to the field,and promotes the total root system in the 0-10cm and 10-30cm layers in the later stage of transplanting,at the same time,it promotes the growth of new roots in the 30-50cm soil layer.(3)Straw returning will aggravate the death of tillers at the turning-green tillering stage.The effect of straw incorporation treatment on rice tiller growth is more serious than that of mulching treatment,and it will increase with the increase in the amount of returning to the field.The tiller is even reduced to zero under the full amount of straw buried and returned to the field(FM3).With the decomposition of straw and the growth of rice.In straw mulching treatment,only FG1 treatment was lower than control treatment in tillers number,and the number of tillers in the incorporation treatment was higher than control.The ear-forming rate reached the maximum and the minimum under the FG1 and FG2 treatments,respectively,and the ear-forming rate decreased with the increase in the amount of returning to the field under the incorporation treatment.Appropriate return to the field can increase rice yield.Under the straw mulching,the thousand-grain weight,seed setting rate,number of grains per ear,and yield of FG2 and FG3 treatments were significantly higher than control treatment.Under the incorporation treatments,the yield components under the full and over-returning treatments were significantly greater than control.From the rice yield,the rice yield reaches the maximum when the amount of straw returned to the field is 6.0t/hm~2(full return to the field),and the straw incorporation is better than mulching treatment.Under the rape-rice planting pattern,the best treatment method for rape straw returning is to incorporation the whole straw to the field.(4)After rape straw returned to the field,the decay rate and nutrient release a quantity to have peaked in the 0-20d,the decay rate range of mulching and incorporation under different nitrogen treatment from 30.87%-33.60%and 33.65%-36.70%,The burial treatment is more conducive to the decomposition of the straw in the early stage.On the 140th day after returning,the degradation rate of straw under the mulching treatment increased with the decrease of nitrogen fertilizer,and the degradation rate of straw under the incorporation treatment increased with the increase of nitrogen fertilizer.The p H of the water first decreases,then increases and then decreases until it finally stabilizes.The amount of dissolved oxygen decreased rapidly within 20 days before returning to the field,and the water body approached an anaerobic state,and gradually increased within 20 days to 100days until it reached a stable state.The amount of dissolved oxygen decreased rapidly within20 days after returning to the field,and the water body approached an anaerobic state,and gradually increased within 20 days to 100 days until it reached a stable state.(5)When the straw powder particle size is 100 meshes,the water swelling performance of the slow-release fertilizer is the best.Among the 5 binders,ammonium persulfate treatment has the best water swelling performance.The effects of different binder treatments on rice plant height,tillers,fresh weight,dry weight and chlorophyll content reached significant levels.Among them,the plant height,tiller and fresh weight under different binder treatments are all lower than those of commercially available fertilizer treatments.Under the treatment of the five binders,polyacrylamide is the best binder for the growth of rice,but the specific nutrient content and ratio need to be further studied.In conclusion,the rapid decomposition and nutrient release of straw in the early stage of returning to the field changed the growing environment of rice,and then affected the normal physiological process of rice roots and aboveground parts,and had adverse effects on the growth of rice roots and the greening and tillering of aboveground parts in the early stage of transplanting.At the later stage of transplanting,with the release of straw nutrients,the growing environment of rice was gradually restored,and then the growth of rice was promoted.In this study,the direct return of straw to the field should be the full amount of straw incorporation to the field.In addition,this paper also made a preliminary study on the new way of straw returning to the field,the results showed that the straw and chemical fertilizer in proportion to produce a new type of compound fertilizer is a more feasible method,the specific formula and the influence mechanism on plant growth need to be further studied. |
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