Potential Of Crop Straw Replacing Potassium Fertilizer In Liaoning Province And Its Application In Greenhouse Vegetables

In order to clarify the potential of crop straw to replace chemical fertilizer in greenhouse vegetable production,the yield and nutrient resources of 13 kinds of crop straw in Liaoning Province were estimated by straw-to-grain ratio method,and the spatial distribution,comprehensive utilization and potential of replacing chemical fertilizer were analyzed and evaluated.At the same time,based on the long-term positioning experiment of organic material（straw,vermicompost）replacing chemical fertilizer in greenhouse of Shenyang Agricultural University,the suitable proportion of organic material replacing chemical fertilizer in greenhouse cucumber production can achieve the purpose of reducing fertilizer and increasing efficiency and is conducive to improving soil potassium supply capacity;furthermore,through the straw decomposition simulation experiment in greenhouse,the straw decomposition law and the response of potassium release characteristics to soil fertility in greenhouse were clarified.In order to provide theoretical basis and practical guidance for the appropriate amount of straw instead of chemical fertilizer in facility vegetable production.The main research results are as follows:（1）In 2018,the amount of straw resources in Liaoning Province reached 2.65×10⁷t,of which the total amount of N,P₂O₅and K₂O nutrients were 2.83×10⁵,8.34×10⁴and 4.20×10⁵t respectively;grain crop straw accounted for 89.04%of the total straw output,followed by other crops（7.00%）and cash crops（3.96%）;the crops with the largest straw yield were corn（69.03%）,followed by rice（15.45%）,vegetables（7.00%）and peanuts（3.60%）.Shenyang,Tieling and Chaoyang are the top three regions in terms of straw volume;Fuxin has the highest yield of peanut straw（2.54×10⁵t）;Tieling has the highest yield of corn straw（3.19×10⁶t）;Shenyang has the highest yield of rice and vegetable straw（9.63×10⁵and3.62×10⁵t）;Chaoyang has the most abundant types of straw resources,and at the same time the yields of sugar beet and sunflower seed straw are the highest.Corn and rice straw,as the main source of straw resources in Liaoning Province,can provide 8.79×10⁴,3.36×10⁴,1.83×10⁵t and 1.58×10⁴,0.81×10⁴,7.91×10⁴t of nitrogen,phosphorus and potassium nutrients respectively,in the season after returning to the field,which can save 1.378 billion and 430 million yuan of chemical fertilizers put in.Liaoning Province is rich in straw resources,and the potential of corn and rice straw to replace chemical fertilizers is high.The available nutrient resources in the current season after returning to the field are considerable,which can replace some nitrogen,phosphorus and potassium fertilizers to achieve the goal of reducing fertilizer application in farmland.（2）Micro-plot experiment of organic material replacing chemical fertilizer in greenhouse showed that proper application of straw or vermicompost could significantly increase cucumber yield and economic benefit,and increase potassium absorption of plant.The amount of straw and vermicompost was 1.54×10⁴～3.07×10⁴and 0.98×10⁴～1.97×10⁴kg·hm^-2,respectively.Compared with 100%chemical fertilizer,the yield and economic benefit of cucumber treated with 50%straw increased by 15.2%and 16.4%,respectively.In the treatment with vermicompost,25%vermicompost had the best substitution effect,and had a gain effect on yield and agronomic traits.Straw and vermicompost input affected soil potassium supply capacity and potassium availability.The combined application of 25%or 50%straw or vermicompost was conducive to maintaining the total potassium content in the soil at a high level,and improving the soil available and slowly-available potassium content during the growth period.The soil with 50%straw or 25%vermicompost had high cumulative potassium release and relatively low potassium fixation,showing strong potassium supply capacity.（3）The simulation experiment of straw decomposition in greenhouse showed that straw decomposition was divided into fast decomposition period（0～60 d）and slow decomposition period（60～120 d）.High（H）and medium fertility（M）soil can promote the decomposition of straw,cellulose and hemicellulose.The cumulative decomposition rate of lignin in high fertility soil was significantly higher than that in medium fertility and low fertility（L）soil.The release patterns of potassium nutrients in straws were similar in different fertility soils,and there was no significant difference in the cumulative decomposition rate of potassium during the decomposition period.After 120 d of decomposition,the average cumulative release rate of potassium was 87.22%～88.63%.The content of available potassium in 20～40cm soil layer increased by 71.37 and 67.37 mg·kg^-1respectively in high and medium fertility soil after 120 days,and decreased by 1.00 mg·kg^-1in low fertility soil.The slowly-available potassium content in the 20～40 cm soil layer of low and medium fertility showed an increasing trend with the increase of incubation time.After 120 days of incubation,the slowly-available potassium content increased by 81.83 and 100.41 mg·kg^-1,respectively,that in high fertility soil only increased by 5.99 mg·kg^-1.Therefore,straw input into medium fertility soil is more conducive to its decomposition and improve soil available potassium pool.