| The balances of competition and interaction of resources between cotton and wheat during the intergrowth period are of importance to determining yield and benefit in cotton-wheat double cropping system, and the competition and interaction of resources between underground organs are paid much attentions by many scientists in this field. At the experimental station of Shandong Agricultural University and the Cotton Research Institute of Chinese Agricultural Academy of Science in the growth season of 2001-2002, wheat variety Lumai 15 and cotton variety Meimian 33B were planted as the cotton-wheat double cropping systems. Total four treatments were implemented, i.e. monocultural system as CK, cotton-wheat double cropping system in which the roots of cotton and wheat mixed (DSRM), DS in which the roots of wheat and cotton were separated with nylon net (DSRN), and DS in which roots of wheat and cotton were separated with plastic film (DSRP). The characteristics of accumulation and distribution of nutrient and dry matter, growth and temporal and spatial distributionof root, root physiology, soil nutrient contents, soil enzyme activities, changes in species and number of microbe in the rhizosphere and non-rhizosphere zones of cotton were studied. The results were as follows: 1 Accumulation and distribution of dry matter and nutrientOver the intergrowth period, accumulation of dry matter and nutrients in cotton with cotton-wheat double cropping system (DS) were lower than than that with monoculture (CK). After harvest of wheat, absorbing of N, P and Kbetween early-bud and bolling stage increased quickly, and was about 5 times higher in cotton plants with DS than that with CK. The accumulation of dry matter showed the same tendency. This indicated that the accumulation of dry matter and nutrients expressed a speedup when the competition between cotton and wheat dismissed after the harvest of wheat. Compared with CK, contents of N, P and K in cotton plant with DS was lower,and the nutrients distributed to vegetative organs were higher, while those to reproductive organs were lower.Accumulation of N, P and K in cotton plants with cotton-wheat double cropping system in which the roots of cotton and wheat mixed (DSRM) and DS in which the roots of wheat and cotton were separated with nylon net (DSRN) were lower than that with DS in which roots of wheat and cotton were separated with plastic film (DSRP). Total accumulation of N and K in cotton with DSRM was lower than that with DSRN.Dry matter of cotton plants with DSRM was the lowest, indicating that the accumulation of dry matter and nutrients was strongly impacted by wheat. After harvest of wheat, the accumulation of nutrients and dry matter in cotton plants with DSRM was still lower than those with DSRN and DSRP. 2 Temporal and spatial distribution of root growthThe changes of root length, root length density, root area and root average diameter of cotton plants showed a single-peak curve with the developmental stages. The stages of the highest root length, root length density and root area showed little difference between cotton plants with interplant systems and single crop system. After bolling stage, however, the decline speed of root area, root length and root length density in soil layers below 40 cm of cotton plants with interplant systems were obviously lower than that with single crop system. The average root diameter showed little difference between cottons with interplant and single crop systems. The dry weights of root in the top soil layers were lower of plants with interplant systems before bolling, while obviously higher after bolling, compared with those of single cropsystem.Within the observed area of 0-25cm apart from cotton, root length, root length density and root area were the highest in the 0-20cm soil layer, and descending with soil layer. In the topsoil layers, root density was the highest at the locations of about 12.5 and 0-7.5cm away from cotton plant with single crop system and interplant systems, res...
|
PDF Full Text Request