Studies On Goosegrass Competition With Cotton And Its Resistance To Glyphosate

Goosegrass [Eleusine indica(L.) Gaertn.] is one of the worst agricultural weeds on a worldwide basis. In China, it is a noxious weed in the cotton field which results in significant yield loss by competition for light, water, feitilizer and space with cotton. The emergence time of goosegrass, its interference on cotton and the usage of herbicides were different in three cotton-producing areas of China. This research focused on the competition between cotton and goosegrass, the biological characteristics and the resistance of goosegrass to glyphosate. The results will be of great significance for establishing reasonable chemical control scheme. The main results were as follows:1. The outdoor pot experiment and field experiment were carried out to determine the effects of fertilizer levels on the competition between cotton and goosegrass during 2014-2015. Results of the pot experiment showed that normal fertilizer treatment could promote the growth of cotton and cwhen the fertilizer rate increases to conventional fertilizer consumption, cotton yield increased.compared with no-fertilizer treatment.nutrition can promote cotton growth and cotton yield, and can improve the competitiveness of cotton to goosegrass. But when the amount of fertilizer increased rate for doublely fertilizer, cotton growth compared were not advantage compared with the conventional normal fertilizer ratetreatment since, insteadmore fertilizer promoted the growth of the goosegrass and enhanced the competitiveness of goosegrass. Density thresholds for goosegrass were 4, 8 and 2 plants/pot that cotton yields significantly reduced under three fertilizer levels, respectively. Cotton fiber character quality were unaffected by weed competition and fertilizer levelnutrients. And the effect of intraspecific competition on the growth and development of goosegrass. The shoot dry weight, tiller number and inflorescence number of goosegrass increased as the increase of soil fertility. Goosegrass plant height, tiller number and single dry weight tended to decrease with the increase of weed density due to intraspecific comprtition under the condition of the same fertility. The results of field experiment showed that cotton yield, stem diameter and dry weight of single plant decreased as the increase of weed denisity when the soil fertility of medium. Cotton growth and yield were not unaffected by N fertilizer levels, but cotton fiber quality were influenced when it’s twice time the level of normal fertilizer. Under the four levels of N fertilizer, the density thresholds of goosegrass at which cotton yields was significantly reduced were 4, 2, 2, and 1 plants·m-1, respectively. The shoot dry weight, tiller number and inflorescence number of goosegrass were not unaffected by weed denisity and N fertilizer levels.2. The outdoor experiments were carried out to determine the the time of emergence on the growth and reproduction of goosegrass. This research showed that the growth and reproduction of goosegrass were affected significantly by the time of emergence. Plants that emerged early in the growing seasons, such as in May, were significantly taller and produced more biomass and seeds than those that emerged in June, July, August and September. Delayed emergence resulted in a shorter vegetative phase and less seed production. Very early sowing in April did not generate any advantage for growth and reproduction of goosegrass due to sub-optimal temperature, while plants that emerged after September did not flower, suggesting that control action is required before September to control the soil seedbank. Delayed emergence had a little effect on thousand seeds weight. Goosegrass species responded to environmental stress in that the whole plant clump began to show plasticity change. Both vegetative and reproductive parts were gradually reduced as the emergence time was delayed, but their rate of change was not synchronized and such change was to increase the chance of producing offspring. For example, the heading rate and reproductive allocation were increased between May and July. These changes were to combat rough environmental conditions, and were also a survival strategy for goosegrass.3. 48 goosegrass populations were collected in cotton field in eight provinces of China, and then the resistance of these weed species to glyhosate was evaluated by whole plant bioassays. The results showed that goosegrass populations from different cotton-producing areas had different levels of resistance to glyphosate. The highest resistant index(RI) was 14.4, which was found in populations from Hanchuan city, Hubei province, followed by the populations of Hukou and Zaoqiang, the resistant index of which were all equal to 11.7. Such information is important to formulate effective weed control methods.