棉花氮肥高效利用生理机制研究

Cotton production, playing an important role in China's national economy, is now facing new problems for its sustainable development, such as rising of production cost (fertilizer comsumption, labor price), low fertilizer utilization rate, high eutrophycation of water body, and stagnation of cotton yield. In which, low fertilizer utilization rate (30 - 35% for N fertilzer) is the fundamental factor..Results including ours indicated that, among the normal 3 splits applications of N, first bloom application (FBA) had the highest N utilization rate, followed by peak bloom application (PBA), and pre-plant application (PPA) had the lowest for the high yielding cotton plant. Therefore, postponing the application of N fertilizer by minimizing the N split ratio for PPA and maxmizing the ratio for PBA enhanced cotton yield, increased the amount of N absorbed, improved the N utilization rate, and at the same time minimized the release of nutrients to the environment..The proposed program is going to, based on the N utilization features of high yielding cotton stated above, adopting the major commercialized cotton variety, 15N isotope tracing technique, under the condition of both pot and field trials, detect the responses of cotton characteristics in its growth progress, yield formation, dynamics of biomass and nutrients accumulation, N metabolism such as N (15N) absorption, transportation, distribution, and transformation (absorption rate, distribution destination and percentage, amount of different N contained chemicals and related enzymes activity), 15N amount retained and scattered in the soil of plowing layer, as affected by the application stage, ratio and rate of N during the flowering and boll setting period - - the period most N absorbed. The purposes of the proposed program are to make awareness in the field of the characteristics of N metablism and N fertilizer utilization for high yielding cotton plant, to understand the relationships between N efficient utilization and N metabolism, and N metabolism and cotton yield formation..Therefore, the proposed research would be beneficial to the effort to develop more efficient technique of fertilization for cotton production, and beneficial to the awareness of cotton physiological mechanism of N efficient utilization as well.

我国棉花生产的持续发展面临新挑战，如生产成本（施肥量、劳动力价格）较高，肥料利用率较低，水体富营养化较重，棉花产量徘徊等。其中肥料利用率低（其中N肥利用率30-35%）是决定因素。.研究表明，高产棉花对初花肥N利用率最高，盛花肥其次，底肥最低；因而减少底肥、增加花铃肥施N比例可提高棉花产量、棉株吸N量、N肥利用率、同时减少环境释放量。基于棉花N肥利用规律，拟采用主推棉花品种、15N示踪、盆栽和大田试验，研究花铃期不同施N时期、不同施N比例、不同施N数量时，棉花生育进程、产量形成、生物质和养分积累动态、N吸收、分配、转化等代谢特性（包括吸收速度、分配方向和强度、不同形态N含量、及相关酶活性动态）、以及15N土壤残留与分布等变化，以了解高产棉花N代谢特点，揭示N肥高效利用与棉花N代谢、N代谢与产量形成之间的联系。.可见本研究有助于探索棉花高效施肥技术、明确棉花高效利用N肥的生理机制。

在前人和本课题组已有研究结果的基础上，采用主推棉花品种、15N示踪技术，在盆栽和大田（中等土壤肥力）试验条件下，研究了推迟播种、增加密度、减少肥料用量时，棉花的适宜施肥（N）时期、适宜施N数量，以及相应条件下棉花生物学特性、营养特性、N代谢特性等。.1.棉花一次施肥适宜时期探讨.固定施N量225 kg/ha（N:P2O5:K2O=1:0.3:1），全部肥料（含15 kg/ha硼砂）于开花后1次施用时期（开花后天数，DAF）设置5个处理：0DAF（开花当天），5DAF，10DAF，15DAF，20DAF，对照（底肥：初花肥：盛花肥=3:4:3）。.大田试验随机区组设计，4次重复，小区面积左右，5月20日直播，密度6株/m2。盆栽试验采用PVC桶（h45 cm，Ф35 cm），装土45 kg/盆。5月20日直播，每盆3株，15N标记。.1.1见花施肥棉花产量达到1130-1380 kg/ha，高于或相当于对照，高于湖北省平均产量。表现为单位面积铃数增加，生物质累积特征值最合理，生物质量最大，向生殖器官分配数量最多；棉田冠层积温较低。.1.2见花施肥棉株对养分累积量最大，累计特征值最合理，向生殖器官的分配量最大；与对照氮磷钾累积动态特征值接近。因此棉花肥料利用效率最高，达到61%。.1.3见花施肥棉花叶柄硝态氮含量维持较高或最高水平，尤其是上部叶片；棉花叶片亚硝态氮、游离氨基酸、可溶性蛋白质、可溶性糖等代谢产物含量水平合理，叶片硝酸还原酶等酶活性较强。.2.棉花一次施肥适宜N肥用量探讨.见花施肥，N肥用量设置5个水平（处理）（kg/ha）：120，150，180，210，240。磷钾肥用量，按N180水平N:P:K=1:0.3:1计算。另外施硼砂15 kg/ha。.大田和盆栽试验设置同前。.2.1N180处理棉花产量最高或较高（1260 – 1370 kg/ha），其差异主要来源于单位面积铃数（盆栽棉花铃重、衣分也有差异），年际间趋势一致。.2.2N180处理棉株生物量最高达到1000 – 1200 g/m2，尤其是其生殖器官生物量达到最大值；其棉株生物质累积特征合理。.2.3N180处理棉株养分吸收量最大，分配到生殖器官的量也最多，年际间趋势一致。