【作者】 Talpur Khalid Hussain；

【导师】 蔡典雄；

【作者基本信息】 中国农业科学院 ， 土壤学， 2014， 博士

【摘要】 小麦和玉米是全世界重要的种植作物,而在中国华北平原是重要轮作种植区域。土壤水分和养分管理是影响华北平原小麦玉米产量和品质的两大主要因素。在华北平原小麦-玉米轮作体系下,不当水氮管理已被广泛报道,特别是当氮施用量到超出植物需要时,会转换成不同形态氮,从而容易挥发到大气中或向下淋溶到土壤中,这样不仅造成经济损失,并且还污染空气和地下水源。在气候变暖和该地区极端降雨天气频度增加背景下,进一步加强水氮管理、减少水氮损失尤为重要。因此,本文重点探讨在气候变化情景下,降水和不同施氮量影响作物生长各部位生物量、产量以及提高其水氮利用效率,为华北平原可持续小麦和玉米高产提供科学依据。两年田间试验设在中国农业科学院廊坊实验站(39°60’27”N,116°60’09”E),土壤类型为碱性沙壤土,实验设计为4个肥料水平(F0=NO PO K0, F1=N120P84K120,F2=N240P168K240,F3=N360P254K360公斤/公顷)、5种降水年型(根据30降水分布资料模拟不同降水年型降水)灌水水平(干旱年W1=483mm/年,欠水年W2=650mm/年,正常年W3=850mm/年,丰水年W4=1200mm/年,实际降水年W5=年间降水+66mm播前水),灌溉水分处理(W1,W2,W3,W4)在移动防雨棚(防止降雨)内进行,降雨水分处理(W5)在露天场地进行。完全随机设计,每个处理三次重复。生长季为2011-12年和2012-13年两个生长季。本文重点是研究不同氮肥和用水对小麦和玉米生长、干物质量、产量的影响,评价在不同气候变化情景下,土壤和植物体各部位氮累积。主要结果如下：水氮影响作物各部位干物质累积量的研究表明：两个生长季(2011-2012年和2012-2013年)小麦在开花期叶片干物质随水分和氮处理水平增加而显著增加；在2012-13年,穗干物质在不同水分及氮处理中显著变化,W4F1产量最高；茎和根干物质也有类似趋势,其中在2011-12年度,所有处理均表现不显著,但在2012-13年,W4F3处理呈显著差异,表现为茎>穗壳>叶>根；在两个生长季节中,氮肥用量和水含量显著影响小麦收获期各个部位干物质量；在2011-12年,在W4F3处理下,籽粒产量达到最大,其次为F2W4,F2W3处理,而2012-13年干旱年,W3F2处理茎秆干物质产量较高；茎干物质量在2011-12年W4F3处理较高,在小麦收获期表现为籽粒>茎>穗壳>根>叶；在两个年度内,F3W4和F2W3处理最大叶干物质重达到最大,然而,在2012-2013年期间F3W4处理的茎秆干物质量较高；在2011-12年F3W4和F4W4处理下根干物质量最高；2011-12年各处理千粒重明显高于2012-13年,但处理间无显著差异。2012年玉米在吐丝期,在W5F2处理具有最大叶和棒轴干物质量,其次为F3F1处理,同样,在W5F3处理下根干物质量较高,吐丝期干物质累积量依次为表现为茎>叶>根>棒轴,而收获期则为表现为籽粒>茎>棒轴>叶>根,但氮和水分水平对株高没有显著影响；F3W5、F2W5处理下到玉米籽粒产量更高,F2W3、F1W4、F3W4、F2W4处理的产量也相对较高,而产量随水和施氮水平增加表现增加趋势。通过各生育期氮转移量NT,氮转移效率NTE,籽粒中来自花期/吐丝期氮的贡献CNS和氮收获指数NHI测算,对小麦和玉米花期/吐丝期和收获期各部位中N吸收和积累的研究表明：2012-13生长季,作物氮素吸收和积累随水分和氮肥施用而增加；在小麦中,大部分土壤氮肥主要在花期吸收,尽管土壤中氮继续保证了植物氮吸收,之后吸收速率稳定或略有下降,在灌浆期各部位氮累积量依次为茎>叶>穗>根,而收获期则表现为籽粒>茎>穗壳>根>叶;在玉米生长期,N吸收在吐丝和收获阶段趋于稳定,在吐丝期,玉米各部位氮累积量依次为茎>叶>棒>根,而在收获期则表现为籽粒>叶>茎>根>棒轴；相对自然降雨水分处理条件下,灌溉水分处理下作物能够吸收更多的氮,特别是在2012-2013年表现更突出；NT、NTE、CNS和NHI显著受水分和氮肥水平影响；在所有水分处理下,NT、NTE、CNS和NHI随氮肥水平的增加而增加,表明氮肥和灌溉影响植物氮的吸收和转运。因此,干旱条件下生长敏感阶段补充灌溉,是提高水分利用率和作物氮吸收量的一个有效管理措施。此外,水和氮肥极大地影响水分与氮的吸收效率,因此有效地利用水分和氮肥将有助于减少过度水和氮的输入,进一步增加净收入。土壤N平衡计算结果表明：无论水肥处理水平、年份和作物类型,铵态氮最高积累量均出现在0-20厘米表层土壤剖面；铵态氮累积量达到最大期的时间,W5F4处理是在2012年小麦收获后,而W5F3和W3F4处理均在2012年和2013年小麦收获后；无论作物和年份,所有土壤剖面深度的硝态氮累积随氮肥料剂量的增加而增加,施肥处理对土壤硝酸盐含量有显著作用；相对施肥处理,未施肥处理土壤硝态氮浓度最低,高施氮肥以及灌溉处理土壤硝态氮浓度最高；由于硝酸盐是组成矿质氮的主要部分,土层中无机氮含量或多或少受施氮肥影响,存在硝态氮积累趋势。每种作物播种前土壤含水量会随灌溉水平和降雨而显著变化。最经济施氮量和灌溉水平均低于最高产量要求的最大施氮和灌溉水平,施氮量在225-330kgha-1和476-638mm总用水量时,小麦可以获得最佳经济产量4849-8838kgha-1,而玉米施氮量在250-345kgha-1和833-1164mm总用水量时,可获得最高经济产量9466-11463kgha-1。在试验年度里,作物水分利用(蒸散)与灌溉量存在线性相关的。WUE随着灌水量增加而降低,低灌溉处理下WUE比高灌溉处理高。试验年度,WUE随施氮量增加而显著增加,施肥氮量到240kgha-1时达到最高。在不同的施氮处理中,N240处理水分利用效率最高。氮肥利用效率随灌溉量增加而增加(表现较好的氮水协同作用),但随施氮量进一步增加而下降,在F3W1处理在所有作物生长季的氮利用效率最低。总之,本研究提供的证据表明,合理水氮管理可以部分抵消气候变化带来的干旱影响,并获取小麦和玉米高产、较高水分和氮肥利用效率的重要措施。更多还原

【Abstract】 Wheat and maize are important grain crops grown worldwide. In China, these crops are mostly grown in north china plains (NCP). The water and nutrient content in the soil are two main factors that affect crop yield and quality. Nitrogen is the main elemental component of nutrient management for crop production; its injudicious use is widely reported in wheat-maize cropping system of NCP. Due to conversion of nitrogen in different forms when it is applied beyond to absorption capacity by plants, it evaporates in to atmosphere or, leaches down into the soil. This results not only economic losses but also pollutes air and adversely affect the underground water quality. Nitrogen losses are further enhanced by warming and infrequent rainfall conditions of this area. So, judicious use of N and water is prerequisite for improving their use efficiencies to sustain high yields of wheat and maize under changing climatic conditions.A two-year field study was conducted in randomized complete block design on sandy loam soil at the experimental farm of Chinese Academy of Agricultural Sciences (39°60’27"N,116°60’09"E) at Lang fang in the growing seasons of2011-12and2012-13. The main objectives of current study were to determine the effect of N fertilization and water levels on growth, dry matter and yield production of wheat and maize and to investigate the N accumulation in the soil and various parts of plants under changing climatic conditions. Four rates of fertilizers (F0=NO P0K0, F1=N120P84K120, F2=N240P168K240, F3=N360P254K360kg ha-1) and five water level (W1, W2, W3, W4and W5) were applied to both crops. Irrigation water treatments for wheat were W1(250.00mm), W2(316.67mm), W3(383.33mm) and W4(483.33mm) and for maize were W1(233.33mm), W2(333.33mm), W3(466.67mm) and W4(616.67mm). These irrigated treatments (W1, W2, W3, and W4) were protected from rainfall with moveable shelter, while rainfall water treatment (W5) was placed in open zone to intercept rain water for both wheat and maize.The results showed that leaf dry matter of wheat at anthesis stage was significantly increased at increasing water and nitrogen levels in both growing seasons (2011-2012and2012-2013). During2012-13spike dry matter was significantly varied at all water levels and nitrogen treatments. However, W4at Fl produced higher yield. The similar trend was observed for stem and root dry matter production. In the first growing season2011-12all water and fertilizers combination levels showed non-significant response. However, in second growing season2012-13, W4at F3level revealed maximum stem and root dry matter production. Generally a trend of dry matter accumulation at wheat anthesis was found in the order of stem>spike>leaf>root. Moreover, same water and fertilizer combination significantly influenced dry matter yield of all investigated parts of wheat crop at harvesting stage during both the growing seasons. Highest grain dry matter was recorded in W4at F3level during2011-12followed by F2of W4and F2of W3, respectively, whereas, it was higher in F2of W3during2012-13. In both growing seasons, W4at F3level produced significantly higher values for chaff dry matter. For stem dry matter production, F3at W4level, showed maximum values in2012-13. Combination of F3and F4at W4level during2011-12proved best for the production of root dry matter. At wheat harvest the order of dry matter accumulation was grain>stem>chaff>root>Leaf.1000kernel weight was higher in all treatments during2011-12compared to2012-13but there was non-significant response among treatments. In maize, at silking stage, maximum leaf and cob dry matter was recorded in W5at F2, followed by F3and F1during2012. Similarly, higher dry matter of root was also measured in W5at F3level. Grain dry matter of maize was observed higher in F3and F2of W5, which also was higher in F2of W3, F2, Fl and F3of W4, respectively during2012than or compare to other water and fertilizers combination levels. Dry matter accumulated in the order of stem>leaf>root>cob at maize silking stage and at harvesting stage order of dry matter accumulation was grain>stem>cob straw>leaf>root. There was non-significant effect of N and water levels on plant height; however, higher grain yield was recorded at increasing level of water and N rate.N uptake and accumulation in various parts of wheat and maize were investigated at anthesis/silking and harvesting stages. In addition, nitrogen translocation (NT), nitrogen translocation efficiency (NTE), contribution of pre-anthesis/silking nitrogen to grain nitrogen (CNS) and nitrogen harvest index (NHI) were also measured. On average, total N uptake and accumulation were increased by irrigation and N fertilization in the second growing season2012-13in both crops. In wheat, most fertilizer N was taken up from at anthesis; then it either stabilized or slightly declined, while soil N contributed further to plant N uptake. At wheat anthesis order of nitrogen accumulation was stem>leaf>spike>root and at wheat harvest nitrogen accumulated in the order of grain>stem>chaff>root>leaf. In maize, N uptake was stabilized both in silking and harvesting stage. At maize silking order of N accumulation was leaf>stem>cob>root and N accumulated in order of grain>leaf>stem>root>cob straw at maize harvest. Compared to rain-fed conditions, more soil and fertilizer N was utilized by the irrigated crop under the irrigation treatments, particularly in2012-13. N parameters including NT, NTE, CNS, and NHI were significantly affected by water and N fertilizers levels. The higher values for these parameters were obtained at increasing N fertilizers levels under all water levels. These results indicated that nitrogen fertilization and irrigation affected the uptake and translocation of nitrogen. Thus, supplemental irrigation, applied at a sensitive growth stage, would be a valuable management practice for improving water-use efficiency and crop N uptake under the dry conditions. Moreover, both factors (water and N fertilization) greatly affect their efficiencies, hence efficient use of these factors will help to reduce the excess use of water and nitrogen input and increases the sufficient net income.Nitrogen content in the soil was calculated; results showed that the highest concentrations of ammonium N were accumulated in0-20cm surface layer of soil profile regardless of water and fertilizer levels, type of crop and year. The water and fertilizer combination of W5F4showed highest accumulations after the harvest of wheat2012and wheat2013, whereas W5F3and W3F4revealed maximum accumulation of NH4-N after the harvest of maize2012and maize2013respectively. Nitrate N accumulations in all depths increased with increasing rate of N in each fertilizer dose despite of crop and year. Fertilizer treatments had the significant effect on nitrate content of soil. The unfertilized plots showed the lowest and the fertilizer N treated plots revealed the highest nitrate concentration with irrigation water. Mineral N content more or less followed the trend of nitrate N accumulation in soil layers as nitrate contributed major proportion of mineral nitrogen.Soil water content before sowing of each crop varied significantly due to irrigation levels and rainfall. The most economical N rates and irrigation levels were lower than the maximum N rates and irrigation levels required for maximum yield. Nitrogen application rate of225-328kg ha-1and475-638mm water were found to be better combination for getting economical yield4849-8837kg ha-1of wheat. Maize produced better yield9466-11462kg ha-1by utilizing economical nitrogen amout of248-345kg ha-1and834-1163mm water. In both years, crop water use (evapotranspiration) was linearly related to the amount of irrigation. The WUE decreased with increasing irrigation application rates. The low irrigation treatment had higher WUE than that of high irrigation treatment. In both years, the WUE increased significantly with nitrogen application rates up to rate of240kg ha-1. The N240treatment had the highest WUE among the various N treatments. Nitrogen use efficiency increased with increasing water application and decreased with increased nitrogen application levels. In all crop seasons lowest values of nitrogen use efficiency were noted in highest fertilizer (F3) and lowest water (W1) treatment combination.In conclusion, the present study provided evidence that proper N fertilization and irrigation management are important strategies to offset climate change effects and to get reasonable yield of wheat and maize with improved WUE and NUE.更多还原