Effects Of Cotton Stalk Returning And Subsoiling On Soil Physico-chemical Properties And Cotton Yield And Fiber Quality In Coastal Saline-Alkali Soil

The experiment was carried out in coastal saline soil at liangcai township of binzhou city in 2015-2016.The experiment was based on 2 years of cotton stalk returning in 2013-2014,setting subsoiling after cotton harvesting in late november 2014.The experiment was carried out with the design of the split area.The main area was stalk returning and no stalk returning,and the secondary area was subsoiling and no subsoiling.To study the effects of cotton-residue incorporation and subsoiling on soil physical and chemical properties in 0-60 cm soil layer,cotton yield and fiber quality.In order to provide an important theoretical support for the continuous cropping of cotton field in coastal saline alkali soil and the large area promotion of cotton stalk returning to the area and the application of subsoiling.1.Effects of cotton stalk returning to soil and subsoiling on soil structure and water contentSuccessive cotton stalk returning significantly decreased soil bulk density in 0-30 cm soil layer and soil micro-aggregates with particle size <0.25 mm in 0-10 cm soil layer,while the content of soil macro-aggregates with particle size >5 mm was significantly increased in 0-10 cm soil layer,compared to control(residue removal).Subsoiling significantly decreased soil bulk density in 10-40 cm soil layer and soil micro-aggregates in 0-30 cm soil layer had no significant effect.There was no significant effect on soil water content in 2 years.2.Effects of cotton stalk returning to soil and subsoiling on soil chemical propertiesIn 0-20 cm soil layer,successive cotton stalk returning significantly increased soil organic matter,total nitrogen,available nitrogen,nitrate nitrogen,ammonium nitrogen and available potassium content,respectively,while the soil salinity and available phosphorus content were reduced compared with control.Subsoiling significantly increased the contents of soil available nitrogen and available phosphorus,while soil organic matter,total nitrogen,nitrate nitrogen,ammonium nitrogen and available potassium were decreased respectively compared with control.The effect of subsoiling on soil salinity was different,which mainly reduced the salinity of cotton budding,flower and boll-forming and boll opening period.In 20-40 cm soil layer,successive cotton stalk returning significantly increased soil nitrate nitrogen and ammonium nitrogen,respectively,while the soil salinity were reduced compared with control.Subsoiling significantly increased the content of soil available phosphorus,while soil total nitrogen,nitrate nitrogen and ammonium nitrogen were decreased respectively compared with control.The effect of subsoiling on soil salinity was different,which mainly reduced the salinity of cotton flower and boll-forming and boll opening period.In 40-60 cm soil layer,successive cotton stalk returning significantly increased soil nitrate nitrogen and ammonium nitrogen,respectively,while subsoiling significantly decreased the soil nitrate nitrogen and ammonium nitrogen respectively compared with control.3.Effects of cotton stalk returning to soil and subsoiling on soil Soil respiration rate and enzyme activity.In 0-20 cm and 20-40 cm soil layer,successive cotton stalk returning and subsoiling significantly increased soil respiration rate,urease,sucrase and catalase activity,respectively,compared with control.In 40-60 cm soil layer,successive cotton stalk returning and subsoiling significantly increased soil catalase activity compared with control.4.Effects of cotton stalk returning to soil and subsoiling on biomass and nutrient content of cottonSuccessive cotton stalk returning and subsoiling significantly increased the bioaccumulation of cotton plants,vegetative organs and genital organs during cotton growth.The accumulation of N,P and K in the cotton growth period was SRS>SR>S>CK,and the economic coefficients of N,P and K were SRS>SR>S>CK.5.Effects of cotton stalk returning and subsoiling on growth,cotton yield and fiber qualitySuccessive cotton stalk returning and subsoiling significantly increased plant height,while shedding rate was decreased.It was not significantly affected on the first fruiting branches,the first fruiting height,fruit number and total fruit number.Successive cotton stalk returning and subsoiling significantly increase cotton seed yield and lint yield.There was no significant effect on single bell weight,clothing points,and fiber quality.