|导师||陈小兵 ; 张立宾|
|关键词||肥料效应模型 氮磷肥 冬小麦 黄河三角洲|
（1）利用盆栽试验，控制盐分水平和施氮水平分别为0.7、1.7、2.7 g/kg和0、135、270、405 kg/hm2，以探讨不同盐分和施氮水平下冬小麦苗期对上述两影响因子的响应及土壤理化性质的影响。结果显示，冬小麦地下部干重首先受到盐分促进作用，随着生长期的延长地下部干重逐渐受氮肥抑制作用。冬小麦地上部干重受盐分的影响晚于地下部干重，且在其生长到54天时盐分的抑制作用强于施氮的促进作用。地上部和地下部全氮主要受施氮影响，在施氮量小于270 kg/hm2时随着施氮量增加全氮含量增加，且施氮首先影响地上部全氮积累，后影响地下部全氮积累。增施氮肥有助于盐渍土改良，可使土壤pH的增加幅度降低，且盐分越高地区其增幅降低越大。当施氮量在270 kg/hm2以下时，土壤中全氮与施肥量成正比；土壤中的NO2-、NO3-也主要受氮肥影响，施氮量增加其含量增加。在冬小麦生育前期（54天），氮盐交互作用仅在冬小麦生长到33天时表现出对地上部干重、地下部全氮和土壤NO2-的显著影响。在含盐量低于2.7 g/kg的盐渍土上种植冬小麦时，氮肥施用量需控制为270 kg/hm2，避免过量施用造成肥料的浪费。
（2）在黄河三角洲地区布置冬小麦“3414”氮磷部分试验，控制施氮量（0、135、270、405 kg/hm2）和施磷量（0、53、105、157.5 kg/hm2），分析在氮磷肥料施用量不同情况下的冬小麦生物量和土壤理化性质。结果显示，在轻度盐渍土上，合理控制氮磷肥施用量可提高冬小麦产量，且氮肥的影响强度大于磷肥。单施氮肥产量提高11.6%，单施磷肥产量提高10.6%，当施氮量和施磷量分别为270和105 kg/hm2时，冬小麦产量达到6339 kg/hm2，提高41.7%。氮磷肥对不同土层和不同土壤理化性质的影响时期不同。氮肥主要影响0 - 20 cm土层土壤理化性质，而磷肥则主要影响20 - 40 cm土层土壤理化性质（除有效磷），且两者的影响时期集中在冬小麦灌浆期之前。氮磷肥料的施入降低了土壤pH的增幅，有助于盐渍土的改良，但磷肥的过量施入易增加土壤次生盐渍化风险。施加氮肥有助于提高土壤NO3-含量，有助于作物吸收，但也增加了养分流失风险。
（3）利用数学模型探讨黄河三角洲地区冬小麦产量与施肥量在线性加平台、一元二次、平方根和二元二次4种不同模型下的拟合效果，以得出最佳肥料模型。结果显示，4种肥料效应模型的拟合结果经检验都达到极显著水平(p < 0.01)。在一元肥料效应模型中，氮磷一元二次模型拟合效果最好。结合拟合度、最佳经济施肥量、经济收益、肥料农学利用率和一元模型的局限性，对比一元与二元模型模型, 后者拟合效果最佳，最佳经济氮磷用量分别为244.1 kg/hm2和94.2 kg/hm2，即氮磷肥配比为2.6:1，经济效益为7432.4元/hm2，氮肥农学利用率为6.2 kg籽粒/kg (N)，磷肥农学利用率为13.8 kg籽粒/kg (P2O5)。根据每年的粮食价格和肥料价格变动，可利用模型进行推算该地区更贴合实际的最佳经济施肥量，以用于科学指导施肥。
; The saline soil in the Yellow River delta is widely distributed, and the land use efficiency is low due to the influence of salinity, soil structure and fertility. Salinity, the main obstacle factor, is extremely unfavorable for crop as the salinity is high. Reasonable application of fertilizer can slow down the salt stress on crops partly and reduce the risk of fertilizer waste and water eutrophication, which is beneficial to the improvement of inefficient agricultural development in coastal areas. At present, the interaction between fertilizer and salinity needs to be further strengthened. In order to obtain the best amount of economic fertilizer, it is necessary to establish the fertilizer effect model of winter wheat in the Yellow River delta.
In this paper, effects of salinity and nitrogen in winter wheat seedling on soil physicochemical properties and winter wheat were discussed by controlling the salinity and nitrogen of pot experiment in the indoor arrangement. To investigate the effect on winter wheat and soil physicochemical properties in mild saline soil, "3414" experiment of nitrogen and phosphorus fertilization experiments was arranged at the same time. Finally, according to the mathematical model, nitrogen and phosphorus fertilizer effects on winter wheat yield was discussed through the "3414" test. The main research contents and conclusions are as follows:
(1) Controlling levels of salinity and nitrogen (0.7, 1.7, 2.7 g/kg and 135, 270 405 kg/hm2) in pot experiment, the effects of soil physicochemical properties and winter wheat were investigated at seedling stage. The results showed that the dry weight of winter wheat was first promoted by salinity, but its growth was gradually inhibited by nitrogen fertilizer. The dry weight of shoot was affected by the salinity, later than the dry weight of the ground, and the inhibition of salinity was stronger than that of nitrogen fertilizer when it grew to 54 days. Total N of shoot and root of winter wheat was mainly affected by nitrogen, and when the amount of nitrogen was less than 270 kg/hm2, the content of total N increased with the increase of nitrogen application rate. Nitrogen affected the accumulation of total N in the shoot, and then affected the accumulation of total N in the ground. Increasing nitrogen fertilizer was helpful to saline soil improvement, which could reduce the soil pH increasing, and the higher salinity was, the lower the growth rate was. When the amount of nitrogen was below 270 kg/hm2, the total N in soil was directly proportional to the amount of fertilizer. The NO2- and NO3- of soil were also affected by the nitrogen fertilizer, the content of which increased with the increase of nitrogen application rate. In the early growth stage (54 days) of winter wheat, the interaction of nitrogen and salinity showed significant effects on shoot dry weight, total N content and soil NO2- in winter wheat growing up to 33 days. When winter wheat was grown on saline soil less than 2.7g/kg, the amount of nitrogen fertilizer should be controlled at 270 kg/hm2, so as to avoid excessive use of fertilizer and cause waste of fertilizer.
(2) In the Yellow River Delta region, "3414" test of nitrogen and phosphorus was arranged. Controlling levels of nitrogen (0, 135, 270, 405 kg/hm2) and phosphorus (0, 53, 105, 157.5 kg/hm2), the effects of soil physicochemical properties and biomass of winter wheat were investigated during the whole growth period of plant. The results showed that the yield of winter wheat could be increased by controlling nitrogen and phosphorus fertilizer on mild saline soil, and the effect of nitrogen fertilizer was higher than that of phosphate fertilizer. The yield of single nitrogen fertilizer was increased by 11.6%, and the yield of single application of phosphorus fertilizer was increased by 10.6%. When the amount of nitrogen and phosphorus were 270 and 105 kg/hm2, the yield of winter wheat reached 6339 kg/hm2, and increased by 41.7%. The effects of nitrogen and phosphorus fertilizer on the physical and chemical properties of different soil layers and different soils are different. Nitrogen fertilizer mainly affected soil physical and chemical properties in 0-20 cm soil layer, while phosphate fertilizer mainly affected soil physical and chemical properties (except available phosphorus) in 20-40 cm soil layer, and their influence period was concentrated before winter wheat filling period. The application of N and P fertilizer decreased the soil pH increase, and it was helpful to the improvement of saline soil. However, the excessive application of phosphate fertilizer could increase the risk of secondary salinization of soil. Applying nitrogen fertilizer helps increase soil NO3- content and helps crop uptake, but also increases the risk of nutrient loss.
(3) Four fertilization models - linear plus plateau, unary quadratic, square root, and binary quadratic, were used to simulate the impact of nitrogen and phosphorus fertilizer on wheat yield to examine the suitable fertilization model for wheat grown on mathematical model in saline soil of Yellow River delta. The results suggested that these four fertilization models reached extremely significant level (p < 0.01) by fitting test. Unary quadratic model of N and P fertilizer was the best among the unary fertilization models. On the base of the fitting degree, best economic fertilizer rate, agronomic efficiency of fertilizer, economic benefits and limitations of unary models, binary model was better compared with unary model. In binary model, the best N and P application amount were, respectively, 244.1 kg/hm2 and 94.2 kg/hm2 with the ratio of N to P at 2.6. In this model, the economic benefit, the agronomic efficiency of N and P were 7432.4 yuan/hm2, 6.2 kg grain/kg(N) and 13.8 kg grain/kg (P2O5). According to the annual grain price and fertilizer price change, the model can be used to calculate the optimum economic fertilizer amount in the region, which can be applied to scientific guidance fertilization.
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