作物水肥利用过程及调控试验研究

节水中心2009届博士研究生杜红霞，在导师吴普特研究员、冯浩研究员、王百群副研究员的指导下，经过三年努力完成了作物水肥利用过程及调控试验研究。

研究方向：水土资源高效利用

摘  要

如何充分利用自然降水和更大限度发挥有限灌溉作用，实现同步提高作物产量和作物水肥利用效率及减少氮、磷肥污染是现代农业发展过程中急待研究的重要课题之一。本研究以夏玉米、冬小麦为供试作物，采用田间试验和土柱模拟试验相结合的方法，研究了水、氮、磷调控措施对夏玉米/冬小麦生长的影响，揭示了作物养分吸收累积和转运规律，调控措施对作物水肥利用效率和玉米根系特性的影响，得出以下主要结论：

1、在无灌溉条件下，氮、磷肥均能提高夏玉米叶面积指数和干物质累积量，随生育期推进，增长趋势逐渐明显，均以氮、磷肥用量分别为240、120 kg.hm-2水平时最好。氮、磷调控未改变茎、叶对氮、磷累积的单峰型动态变化规律，但能增加玉米植株各器官氮、磷累积量，且氮、磷肥配施效果更好。夏玉米植株对氮、磷吸收规律相似，拔节和灌浆期是两个高峰期，氮累积量随施氮量增加而增大。氮、磷调控措施下，夏玉米磷素累积最大速率出现时间较氮素晚，且氮、磷分别为240、120 kg.hm-2水平时最高，分别为1.66和0.29 g?d-1?m-2。

2、夏玉米土壤剖面水分和硝态氮随深度的变化趋势基本一致，0~50 cm土层水分和硝态氮含量高，且呈降低趋势，50~110 cm土层含量低且波动小，灌浆期两者均达到最低值。随施氮量增加，成熟期土壤中硝态氮含量急剧上升；随施磷量增加，土壤硝态氮呈先增后减趋势。0~50 cm土层含水量施氮低于不施氮处理，50~110 cm土层则相反。氮、磷肥能提高夏玉米水分利用效率，并以氮、磷肥用量分别为240、120 kg.hm-2水平时最好。

3、氮、磷肥能显著提高夏玉米产量，随施氮量增加其增幅呈先增后减趋势。当施磷量增至120 kg.hm-2水平时，产量有下降趋势。夏玉米达到最高产量时的氮、磷肥用量分别为：259.40、116.92 kg.hm-2，且氮肥对产量影响大于磷肥。氮、磷配施亦能提高玉米植株吸氮量和氮收获指数，氮、磷肥用量分别为240、120 kg.hm-2时最高，并可减小土壤氮素损失，提高籽粒品质。氮肥利用率与氮素利用效率均随施氮量增加而减小。

4、水、氮及以秸秆为主要原料的新型土壤改良剂均能提高冬小麦干物质累积量，秸秆改良剂与288 kg.hm-2氮肥配施时可提高37.8 %，但未改变其累积规律，拔节和灌浆期是两个累积高峰期，分别占16.7 %~25.5 %、49.8 %~58.7 %。施加秸秆改良剂可提高冬小麦光合速率和叶片水分利用效率。冬小麦茎、叶中氮、磷含量随生长期延续减小，成熟时钾大量贮存于茎秆中。秸秆改良剂和氮肥均能显著提高氮、磷在茎叶和籽粒中的含量以及植株氮、磷累积量，对钾含量影响不明显，且两者配施再配以灌水效果更好。氮、磷出现最大累积速率时间较对照早，无灌水条件下氮素最大累积速率出现时间随施氮量增加而提前，灌水则反之。氮素最大累积速率出现时间较磷早。灌水条件下秸秆改良剂与288 kg.hm-2氮肥配施处理和其与160  kg.hm-2氮肥配施处理氮、磷最大累积速率最高。叶对氮、磷转运量和转运效率均小于茎杆，氮素转运量较磷素多。

5、高氮肥与秸秆改良剂配施冬小麦增产效果显著，配以灌水后增产10.77 %。水、氮及秸秆改良剂能改善冬小麦返青和成熟期土壤水分和硝态氮含量，返青期0~100 cm土层水分变化剧烈，成熟期反之。秸秆改良剂与氮肥配施后0~200 cm土层蓄水量增幅较大，配以灌水更为显著。施氮量越多土壤中硝态氮累积量增幅越大，且对0~30 cm土层影响较大，灌溉后此层含量稍有降低。冬小麦氮素利用效率、氮肥利用率及氮素生产力均随氮施入量增加而降低。单施秸秆改良剂或氮肥对冬小麦水分利用效率影响不大，两者配施能使其显著提高，且秸秆改良剂与288 kg.hm-2氮肥配施处理最好。

6、夏玉米土柱模拟试验结果发现，水分对根系干重、根系活力、根系表面积的影响较氮、磷肥大。根系干重随土层深度增加而减小，0~10 cm土层尤为明显。0~20 cm根长密度较高，根长密度随土层深度增加先减小后上升。根系干重和根长密度随施氮量增加而降低，随施磷量增加一直增长，且玉米根冠比有减小趋势。氮肥和磷肥能提高玉米根系活力，在水分较好情况下其对磷肥更为敏感。

7、由籽粒产量和根系各指标之间相关分析可知，根干重、根长密度、根表面积和根系活力与籽粒产量和玉米地上部分干物质量均呈极显著相关关系。根冠比只与地上部分相关。根表面积和根系活力之间呈极显著相关关系。根系活力和根系吸氮能力对玉米生长和籽粒的形成有很重要的作用，存在显著正相关性。

8、结合各种调控措施对夏玉米/冬小麦籽粒产量及水肥利用效率影响，从控制土壤硝态氮积累量和减小氮素损失综合考虑，夏玉米适宜施氮量范围是120~240 kg.hm-2，施磷水平为120 kg.hm-2；在有限的灌水条件下，秸秆改良剂和氮肥配施能有效地为冬小麦生长提供良好的生长环境。

关键词：水、氮、磷调控；秸秆改良剂；养分累积量；根系；水肥利用效率

AN EXPERIMENTAL STUDY ON UTILIZATION AND REGULATION OF WATER AND FERTILIZER OF CROPS

ABSTRACT

It is one of the important subjects in the development of modern agriculture that how to make full use of natural precipitation, give full play in limited irrigation conditions, improve crop yields as well as water-fertilizer use efficiency synchronously, and reduce continuation of nitrogen and phosphorus fertilizer. Taking summer maize and winter wheat as experimental crop and by using combination research method of field experiments and earth column simulation, this paper has researched the influence of different adjustment measures of water, nitrogen as well as phosphorus on summer maize and winter wheat, nutrient uptake, transfer regularity, water-fertilizer use efficiency, and physiological characteristics of maize roots.

The contents and major conclusion of this paper are as follows:

1、Under the condition of no irrigation, nitrogen and phosphorus fertilizer can improve the leaf area index as well as cumulant expansion of dry matter above ground parts of summer maize, and the growth trend is gradually significant following the growth stage, moreover, the situation reached the summit at 240 kg.hm-2 and 120 kg.hm-2 of nitrogen and phosphorus fertilizer respectively. When nitrogen and phosphorus cumulant expansion is single peak type, nitrogen and phosphorus regulation do not modify the dynamic change law of stem and leaf, but they can increase the nitrogen and phosphorus cumulant expansion of different organs of maize plant, and the effects are better if nitrogen and phosphorus fertilizer are used cooperatively. The absorption regulation of nitrogen and phosphorus is similar in summer maize plant, i.e., jointing stage and filling stage are two peak periods, and nitrogen cumulant expansion shows increase tendency following the increase of nitrogen application rate. Under the regulation measure of nitrogen and phosphorus, the appearance time of maximal rate of phosphorus cumulant expansion of summer maize is later than nitrogen, moreover, the nitrogen and phosphorus cumulant expansion are highest when they are at the level of 240 kg.hm-2 and 120 kg.hm-2, reaching 1.66 g?d-1?m-2 and 0.29 g?d-1?m-2 respectively.

2、Following the changing of depth, the variation tendency on soil profile water and nitrate nitrogen of summer maize is basically identical, i.e., the water and the content of nitrate nitrogen are high and show decreasing tendency in 0 to 50 cm soil layer, also the water and the content of nitrate nitrogen are low and little fluctuation in  50 to 110 cm soil layer, moreover, they all reach to minimum in filling stage. Following the increase of nitrogen application rate, the content of nitrate nitrogen in soil of mature period is a steep rise, and following the increase of phosphorus application rate, the content of nitrate nitrogen in soil first increased and then decreased. Nitrogen treatments is lower than no nitrogen treatments of soil moisture content in 0 to 50 cm, but the situation of soil moisture content in 50 to 110 cm is opposite. Nitrogen and phosphorus fertilizer can improve the water use efficiency of summer maize, and the effects are best when the nitrogen and phosphorus amount is 240 and 120 kg.hm-2 respectively.

3、Nitrogen and phosphorus fertilizer can improve the yield in summer maize, and increase amplitude first increased and then decreased following the nitrogen application rate. When the phosphorus application rate increases to 120 kg.hm-2, the yield shows decrease tendency. Moreover, the yield of summer maize reaches the highest when the application rate of nitrogen and phosphorus is 259.40 kg.hm-2 and 116.92 kg.hm-2 respectively, and the influence on yield of nitrogen fertilizer is greater than phosphorus fertilizer. With nitrogen and phosphorus fertilizer cooperating application, nitrogen uptake and N harvest index of maize plant can be improved, reaching the highest level when the application rate of nitrogen fertilizer and phosphorus fertilizer reaches 240 kg.hm-2and 120 kg.hm-2 respectively, moreover, soil nitrogen loss can be reduced, also grain quality can be increased. The utilization rate of nitrogen fertilizer and phosphorus fertilizer all decreases following the increase of nitrogen application rate.

4、Water, N fertilizer, and the new soil conditioner that mainly material was straws (PJG) can improve accumulation of dry matter of winter wheat, PJG was mixed with 288 kg.hm-2 N fertilizer, it was increased 37.8 %, but it hasn’t change the accumulation regularity. Jointing stage and filling stage is 2 accumulation peak period, accounts for 16.7 %~25.5 % and 49.8 %~58.7 % separately. Applied with the straw modifier can improve the photosynthesis rate and water use efficiency of blades. N, P content of winter wheat stem and blades decreases with the pro-long of growth period. K content is high in mature winter wheat. Straw modifier and N fertilizer can significantly increase the N 、P content and N, P cumulates in stem and blades. It has litter influence on K content in stem and blades. The beginning time of maximum accumulation rate of N and P is earlier than that of CK. Under the condition of no-irrigation, the beginning time of maximum accumulation rate of N advances with the increasing of nitrogen rate and it is opposite to irrigation. the beginning time of maximum accumulation rate of N is earlier than that of P. Under the condition of irrigation, the maximum accumulation rate of N and P is highest which applied by straw modifier and 288 kg.hm-2, 160 kg.hm-2nitrogenous fertilizers. N and P transportation amount of leaves is lower than that of stem, and N transportation amount is higher than that of P.

5、The combined application of high N fertilizes and straw modifier can increase the yield of winter wheat remarkable. The yield is increased to 10.77 % after irrigation. Water, N and straw modifier can improve the water and Nitrate N of winter wheat during green stage and mature stage. Soil moisture of 0~100 cm changes strenuous during green stage, on the contrary, it's in mature stage. After combined application of Straw modifier and N fertilize, water storage of 0~200 cm increases greatly. Accumulation of Nitrate N increases greatly under the condition of large nitrogen rate. Nitrogen rate has great influence on 0~30 cm soil layer and Nitrate N of 0~30 cm soil layer decreases after irrigation. Nitrogen use efficiency of winter wheat and nitrogen productivity decreases with the increasing of N application. Single application of straw modifier or N fertilizer has little influence on water use efficiency of winter wheat. But combined application of high N fertilizes and straw modifier can increases water use efficiency of winter wheat significantly. Combined application of 288 kg.hm-2 N fertilizes and straw modifier Straw has the best effect on water use efficiency of winter wheat.

6、Water has more significant influence on dry weight, activity and surface area of root than that of N and P fertilizer in soil column simulating of summer maize. The dry weight of root decreases with increasing of soil depth, especially the 0~10 cm of soil depth. Density of 0~20 cm root length is large. Fist increase and then decrease with the increasing of soil depth. Dry weight and root length density decreases with the increasing of N application rate and increases with the increasing of P application rate. The root-shoot ratio of maize has a decreasing tendency. N and P fertilizer can improve the root activity of maize and the maize activity is sensitive to N fertilizer in the condition of better water.

7、According to the correlation analysis between grain yield and root, root dry weight,  root length density, combined root area and root activity have a very significant correlation with grain yield and dry matter quantity above ground. Ratio of root weight only has a correlation with that of above ground. Combined root area has a very significant correlation with root activity. Root activity and the nitrogen absorption of root have an important role on maize growth and grain formation and there was a significant correlation.

8、combining with the influence of different regulation measure on grain formation and utilizing efficiency of water, considering with the regulation of nitrate-nitrogen accumulation and decreasing the nitrogen loss, the paper suggests that the range of N application is 120~240 kg.hm-2, P application is 120 kg.hm-2. Under the condition of limit irrigation, straw modifier and application of 160 kg.hm-2 N fertilizers can provide a better growth environment effectively for winter wheat. 

KEY WORDS：Regulation water, nitrogen and phosphorus, New straws soil conditioner, nutrient accumulation, root, water-fertilizer use efficiency