适宜膜下滴灌频次提高北疆机采棉光合能力及产量

在北疆大田条件下,以机采棉品种新陆早57号为供试材料,研究不同灌水分配对机采棉光合特性和产量形成的影响。试验设滴灌定额为4 500 m~3/hm~2,3个灌水分配次数分别为10次(D10)、8次(D8)、6次(D6)。结果表明:D6处理头水时间推迟,由非气孔限制因素导致净光合速率的下降,胁迫程度较高,最大光化学效率、光化学猝灭系数、光化学量子产量显著低于其他处理(P0.05),非光化学淬灭系数明显增加,同时恢复能力较差,地上部分生物量积累受限。盛蕾后充分供水但并没有较高的补偿强度,且蒸腾速率较高,叶片水分利用效率降低。由于D10处理花铃期灌量分配不合理,净光合速率的下降主要受气孔限制因素影响,棉株受到轻度胁迫,吐絮期的灌水有效提高了其光化学猝灭系数,与D6处理差异显著。降低了非光化学淬灭系数,延长了叶片光合功能期,生物量积累偏向营养生长,使其营养器官显著高于其他处理,但生殖器官差异不显著(P0.05),不利于产量的形成。而D8处理在整个生育期保证了高效的光合生产能力,明显提高了光合物质向生殖器官运移的比例,比D10、D6处理高出21.1%、23.5%,叶片水分利用效率表现最优,且产量与D10差异不显著,但比D6处理显著高647.4 kg/hm~2(P0.05)。因此在滴灌定额为4 500 m~3/hm~2的条件下,配合D8处理的灌水分配方式,有利于提高叶片光合能力,促进光合物质优先向生殖器官分配,从而获得高产。由此可见,盛蕾前灌头水且增加盛花期后灌溉定额,同时减少吐絮期水分供应,可有效提高叶片光合生产能力,促进光合物质优先向生殖器官运移,实现机采棉节水高产高效。

Optimal irrigation frequency improving photosynthetic characteristics and yield of machine-harvested cotton with drip irrigation under mulch in Northern Xinjiang

Due to the unique geographical environment, North of Xinjiang is exceptionally early mature cotton region with short cotton growing season. Therefore, how to achieve efficient allocation of irrigation water saving and high yield efficiency of cotton production in the short growth period has become a key problem in the production of cotton in northern Xinjiang. This study investigated the effects of irrigation treatments on photosynthetic characteristics and yield of machine-harvested cotton. An experiment was carried out in the year of 2015 in Xinjiang Agricultural University Experimental Base (44°39′N、86°08′E with an altitude of 367 m) of Changji by an single factor randomized block design. Three irrigation times of 10 (D10), 8 (D8) and 6 (D6) were designed following local experience. The total irrigation quota was 4500 m3/hm2. The machine-harvested cotton variety of Xinluzao 57 was for the experiment. During the experiment, soil moisture content, photosynthetic parameters, fluorescence parameters and yield formation characteristics were measured. The results showed that the D6 treatment delayed the time of first water, and its stress degree was higher than those of the other treatments. For the D6, the non-stomatal limitation caused the decrease in the net photosynthetic rate, the max photochemical efficiency, photochemical quenching coefficient and photochemical quantum yield of photosystem Ⅱ were also significantly lower than those of the other treatments. Meanwhile, the non-photochemical quenching coefficient was increased dramatically, while the recovery capability was poor, which limited the accumulation of above-ground biomass. Due to unreasonable irrigation water allocation at flowering and fruiting stages in the D10 treatment, the net photosynthetic rate decreased as affected by stomatal limitation factors under light water stress, while photochemical quenching coefficient was improved effectively by irrigation in the boll opening stage. At the same time, leaf photosynthetic function duration was extended while the biomass was accumulated more for the vegetative growth and the vegetative organs biomass were higher than the other treatments, which resulted in no significant difference in biomass of the reproductive organs. The D8 treatment could ensure the higher efficient photosynthetic capacity during the whole growth period, and the biomass of reproductive organ was 21.1% and 23.5% than the D10 and D6, respectively. Water use efficiency of leaf in the D8 reached the highest among the treatments, and the yield of D8 was not significantly different from the D10 (P>0.05), but 647.4 kg/hm2 higher than the D6 (P<0.05). Therefore, under the condition of drip irrigation quota for 4500 m3/hm2, the irrigation allocation method in the D8 treatment was beneficial to improve the photosynthetic capacity of the leaves and promote the distribution of the photosynthetic material to the reproductive organs. Therefore, irrigation before the full budding stage, increasing irrigation quota after the full flowering stage and reducing the water supply in the boll opening stage can effectively improve the photosynthetic capacity of leaves, promote the migration of the photosynthetic substances into the reproductive organs, so as to fulfill the water saving goal and achieve high efficiency of machine-harvested cotton production as well.