| With insect-resistant transgenic Bt (Bacillus thuringiensis) cotton 33B (here in afterreferred to as the 33B) and Nongdamian 6 (here in after referred to as the Nong 6) asexperimental materials, growth and development and characteristics of senescence wereresearched on three different tillage treatments: plowing, rotary tillage, direct drilling. Thisstudy, which was aimed to find out the tillage methods of staying senescence of cotton,would help to provide scientific criterion for cultivation of high yield and highquality of cotton. The results were as the follows:1. The effect that plowing altered the structure of plough layer was the strongest, thesoil bulk density of plowing was the least, the soil bulk density of direct drilling was themost, and that of rotary tillage was in the middle. The soil bulk density of plowing androtary tillage increase along with time processing, that of direct drilling descend ratherish.2. Plowing not only boosted the content of chlorophyll and dissolvable protein of themain stem leaf and fruit branch leaf, but also kept strong physiological function in latergrowth period.The order of the content of MDA in the main stem leaf and fruit branch leafwith different treatments was direct drilling＞rotary tillage＞plowing. The content ofchlorophyll and dissolvable protein of the main stem leaf and fruit branch leaf in latergrowth period in Nong 6 were greater than that of 33B, the content of MDA in Nong 6 wasless than that of 33B. The activity of SOD and POD under plowing were the most, there isno significant rule between rotary tillage and direct drilling. The order of the activity ofCAT was also direct drilling＞rotary tillage＞plowing. The photosynthesis ratio of functionleaves on main stem had the rough trend: plowing＞rotary tillage＞direct drilling.3. The orders of the plant height, the main stem diameter of the plant and the leaf areaindex with different treatments were all plowing＞rotary tillage＞direct drilling. The numberof the decayed bolls per cotton plant had the same trend. The plant height, the main stemdiameter of the plant, the leaf area index and the number of the decayed bolls per cottonplant in Nong 6 were greater than that of 33B.There are some effects on the procreatingcourse with different tillage treatments: the growth stages after the buding stage wereadvanced under plowing and rotary tillage.4.The dry matter weight of cotton plant with different tillage treatments had thetrend: plowing＞rotary tillage＞direct drilling.The difference among the different treatmentswas increasing along with the procreating course processing. The dry matter weight of leaves, main stem and branch, bud and bell had the same trend: plowing＞rotarytillage＞direct drilling. The dry matter weight of the whole cotton plant, leaves, main stemand branch, bud and bel in Nong 6 were greater than that of 33B.5. Different tillage treatments had some effects on the dry matter weight of root.Compared with rotary tillage and direct drilling, plowing boosted the dry matter weight ofroot. Direct drilling boosted remarkably the dry matter weight of root in the 0-10cm depthsoil and the proportion in total amount, and plowing boosted remarkably the dry matterweight of root in the 20-40cm depth soil and the proportion in root's total amount. Thetrend of weight of root bleeding sap with different treatments was plowing＞rotarytillage＞direct drilling, the content of phosphorus and amino acid in root bleeding sap hadthe trend: drilling＞rotary tillage＞plowing, but the total amount of phosphorus and aminoacid in root bleeding sap had the same trend as the weight of root bleeding sap.6. The number of bolls per plant and the seed cotton yield and lint cotton yield had thesame trend: plowing＞rotary tillage＞direct drilling. The seed cotton weight per boll ofplowing was most, there are differences between rotary tillage and direct drilling withdifferent varieties. The order of lint percentage with different treatments was plowing＜rotary tillage＜direct drilling for 33B, plowing＞rotary tillage＞direct drilling for Nong 6.The number of bolls per plant and the seed cotton weight per boll, the cotton yield and thelint percentage in Nong 6 were higher than that of 33B.According to all above analysis, it can be concluded that: compared with rotary tillageand direct drilling, senescence manifestation of plowing was slightest, plowing was thebest tillage treatment, we should reduce the area of rotary tillage and advocate plowing inplanting cotton in field to create a favorable soil condition for preventing prematuresenescence of cotton.
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