| The study was conducted at Dezhou Economic Development Zone with two treatments(straw returning soil and no straw returning soil) in 2014-2015. Each treatment was provided with three replicates and each cell area was 957 square meters(33 m length, 29 m width). The dry weight of returning straw to field is about 3500 kilograms per hectare. The cotton variety Denong 09068 was used to research the effects of cotton straw returning soil on soil physicochemical properties, microbial characters, cotton growth status, cotton yield components and fiber quality of cotton, in order to offer theoretical knowledge for larger area application and extention of cotton straw returning soil. The key results were listed below. 1. Effect of cotton straw returning soil on soil physical propertiesCotton straw mixed soil after returning into soil, weakened the soil capillary effect, thereby blocking the loss of water in deep soil, and improved the water content of the soil, comparing to no straw returning treatment. Cotton straw returning soil decreased volume weight of soil across 0–30 cm soil layer in 2014-2015, comparing to no straw returning treatment, the difference was significant at the 0-10 cm soil layer in 2014. Cotton straw returning soil improved >5mm aggregate percentage significantly, reduced the <0.25 mm micro-aggregates percentage at the 10-20 cm soil layer, while straw returning soil had no apprecible impact on soil different aggregates percentage at 0-10 cm and 20-30 cm soil layer, comparing to no straw returning treatment. 2. Effect of cotton straw returning soil on soil chemical propertiesSoil organic matter content, alkaline hydrolyzed nitrogen content and available potassium content after cotton straw returning soil significantly increased comparing to no straw returning soil treatment. The two years? results investigated that cotton straw returning soil had no great influence on soil available phosphorus content. The content of soil available phosphorus was gradually lower than the beginning of the test soil as time goes on. Cotton straw returning is beneficial to reduce the loss of soil Mo and Mn elements. 3. Effect of cotton straw returning soil on soil microbial propertiesCotton straw returning soil significantly increased the quantity of total microbe by on average 19.87%(0-20 cm), 20.07%(20-40 cm) and 56.15%(40-60 cm), including soil bacteria and fungi quantity significantly increased by on average 20.91%, 26.38%(0-20 cm),20.59%, 31.18%(20-40 cm) and 56.85%, 32.30%(40-60 cm), respectively, comparing to no straw returning soil treatment; soil actinomyces quantity increased by on average 4.29%(P>0.05), 11.62%(P<0.05) and 54.00%(P<0.05) at 0-20 cm?20-40 cm and 40-60 cm soil layers, respectively, comparing to no straw returning treatment. Cotton straw returning soil had no appreciable impact on soil urease activities at 0-20 cm soil layer, comparing to no straw returning soil treatment, while straw returning soil increased soil urease activities across 0-20 cm and 20-40 cm soil layer by on average 13.43% and 23.03% significantly, respectively. Soil microbial C and active microbial biomass after cotton straw returning soil significantly augmented across 0-60 cm soil layers. Cotton straw returning soil significantly increased soil respiration rate across 0-20 and 20-40 cm, while straw returning soil had no significant effect on soil respiration rate at 40-60 cm soil layer. Soil sucrase activities after cotton straw returning soil significantly increased by 27.08%, 46.96% and 57.59% across 0-20 cm, 20-40 cm and 40-60 cm soil layers, comparing to no straw returning soil treatment. Cotton straw returning soil significantly increased soil catalase activity at 0-20 cm soil layer by on average 8.73%, comparing to no straw returning soil treatment, while straw returning soil had no great influence on soil catalase activity across 20-40 and 40-60 cm soil layres. 4. Effect of cotton straw returning soil on cotton growth and development, cotton yieldcomponents and fiber qualityCotton straw returning soil increased plant height, first branch height, fruit branch and fruit node of cotton, comparing to no straw returning treatment, while cotton straw returning soil had no appreciable impact on first branch location and shedding rates. Cotton straw returning soil significantly enhanced seed cotton yield and lint yield, absolutely owning to larger total boll numbers and boll weight, but there was no marked effects to lint percentage and fiber quality, comparing to no cotton straw returning field. |
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