【作者】 廖育林；

【导师】 郑圣先；

【作者基本信息】 湖南农业大学 ， 植物营养学， 2010， 博士

【摘要】 本文以农业部望城红壤水稻土生态环境重点野外科学观测实验站长期肥料定位试验为平台,研究了稻—稻—冬闲连作下长期稻草和化学钾肥施用模式对红壤水稻土壤钾素形态变化、土壤钾的吸附与解吸特征和含钾粘土矿物的组成变化和转化过程的影响,探讨了长期施用化肥和稻草条件下土壤钾素形态变化特征,外源钾、土壤粘土矿物组成与作物吸钾量的相互关系,阐明了红壤稻田土壤供钾性能的变化特征、钾素固定与释放规律和钾素容量与强度的关系,为钾肥在稻田土壤上的合理和有效施用提供理论依据。主要研究结果如下：长期施钾的NPK和NPK+RS处理不同土层中土壤全钾、缓效钾和速效钾含量均高于NP和NP+RS处理的相同土层；经27年54季水稻种植后,长期施钾处理土层0—45cm的交换性钾含量增加,而全钾处于亏缺状态。在缺钾红壤水稻土长期双季稻种植制度条件下,即使每年两季水稻施用199.2 K kg/hm2的化学钾肥和4.2t/hm2稻草(含K109.2kg)进入土壤的钾量,还是不足以维持土壤的全钾库；长期每年施用4.2t/hm2稻草(含K109.2kg)而不施用化学钾肥也难维持土壤速效钾的水平。长期施用钾肥和稻草条件下,各施肥处理土壤中非交换性钾的释放都存在2个不同的阶段：即初期的直线上升阶段和后期的缓慢增长阶段。5个施肥处理中,长期不施钾(CK和NP)土壤的非交换性钾累积释放量较小,分别为62.22 mg/Kg和56.12 mg/Kg,长期施钾(NPK、NP+RS和NPK+RS)土壤的非交换性钾累积释放量较大,分别为67.52mg/Kg、64.41mgKg和75.33mg/kg,施稻草(NPK+RS和NP+RS)土壤明显高于对应不施稻草的(NPK和NP)土壤,这可能与长期施用稻草促使土壤矿物钾中的一部分向非交换性钾转变有关。用抛物线扩散、零级反应、一级反应和Elovich方程对土壤非交换性钾的释放动力学过程进行了数学模拟,其中Elovich方程能比较好地模拟5个施肥处理供试土壤非交换性钾的释放动力学。从释放速率和土壤非交换性钾释放给植物的实际考虑,分段直线方程所描述的土壤K释放较上述四种动力学方程更可靠,更准确。分解X-射线衍射图表明,粘土矿物学随施肥处理而变化,在长期施用NP肥的基础上配施K肥或稻草能提高土壤中的伊利石含量,而长期不施K肥却耗竭了土壤中的伊利石含量。从土壤组成的变化来看,全粘粒部分(<5umm)比细粘粒部分(<lumm)与施肥处理的土壤组成变化更加相对应,长期施肥似乎把混层伊利石—绿泥石矿物中CH(绿泥石)变成了游离伊利石和层间伊利石,最大效应是形成了结晶不良伊利石(PCI)。粘土矿物学的变化反映在K+的吸附方面,长期施用化肥或稻草引起K+吸附的变化。通过去除土壤有机质[+H2O2]比较研究表明,特别是在低K+溶液浓度下,土壤有机质对K+吸附为正效应。在高K+浓度下,土壤有机质能够减少粘土矿物对K+的吸附,但土壤矿物在K+吸附中起的作用比土壤有机质更重要,施肥处理土壤矿物组成的变化对K+吸附潜力的影响较大。其中,结晶不良伊利石(PCI)衍射峰面积百分率与K+的吸附潜力(M)和吸附系数(K)之间呈显著相关。在加入外源钾浓度0.4～4.0g/L的范围内,土壤固钾量均随着加入外源钾浓度的增加而增大。5个施肥处理的固钾能力存在差异,与试前土壤相比,长期不施钾(CK和NP)处理土壤的固钾能力增强,长期施钾肥或稻草(NPK、NP+RS和NPK+RS)处理土壤的固钾能力降低,说明长期施用钾肥和稻草是影响土壤固钾能力的重要原因,施钾量高的处理土壤的固钾能力低。在高强度稻-稻种植条件下,水稻作物从土壤中带走大量的钾。长期不施用钾肥,会导致土壤钾素的严重耗竭，此后施入的钾则会被土壤固定,导致钾肥对当季作物的有效性降低。当土壤中钾含量相对较高时,施入钾肥则不易被吸附固定。如果施入的钾不能及时被作物吸收利用,则极易被淋失。长期施用钾肥和稻草后,土壤速效钾和缓效钾含量增加,土壤的固钾能力降低；另外,长期施用钾肥和稻草引起土壤K+饱和度的增加,也使土壤的固钾能力降低。长期不施钾处理土壤的-ΔK°和ARek降低,PBCk值提高,即土壤的易释放钾库变小,土壤对钾的吸附能力增加,土壤供钾能力降低,提高长期不施钾土壤溶液中钾素的浓度需要施用大量的钾,长期施用稻草对0—15cm耕层土壤K的行为有明显影响。土壤中K的形为明显受有机质增加和pH降低的影响,通过拟合PBCk=CEC×KG证明。BaCL2提取阳离子的总和或BaCL2测定的CEC是Q/I曲线线性部分的最好预测公式,有机质能增加固定高亲和K+位。本研究的数据也证明,释放进入土壤溶液的大量K+并非由K+-Ca2++Mg2+来控制,而是由K+-NH4+来控制.施钾能显著地提高水稻产量,施钾肥的NPK和NPK+RS处理27年的早稻平均产量分别比NP和NP+RS处理增加15.2%和10.9%；晚稻增产17.2%和9.1%；在27年54季水稻种植期间,不同施肥处理早、晚稻产量的变化趋势不同。CK、NP处理的早、晚稻产量随时间的推移呈负变化趋势,而NPK、NP+RS和NPK+RS处理的早、晚稻产量呈正变化趋势。稻草还田对水稻具有显著的增产作用,稻草还田的NP+RS和NPK+RS处理的平均水稻产量比单施NP和NPK化肥处理分别增产12.2%和6.7%,稻草的增产作用还随着稻草还田时间的延长而逐年提高。稻草还田携入的钾与化学钾肥具有相同的营养功能,稻草可替代部分化学钾肥。更多还原

【Abstract】 A long-term field experiment was conducted to study the effect of long-term application of K fertilizer and rice straw on the change of form, adsorption and desorption characteristics in soil K, the composition change and transformation process of K-bearing minerals based on double rice and winter fallow cropping system from the Key Field Monitoring Experimental Station for Reddish Paddy Soil Eco-environment in Wangcheng, Ministry of Agriculture, China. The relationship between the change characteristics of soil K form, external source K, composition of soil clay mineral and crop K uptake under long-term application of K fertilizer and rice straw were discussed. In order to reveal the significance of long-term application of K fertilizer and rice straw on K supply capacity and crop growth characteristics, the change of K supplying-capacity, the characteristics of K fixation and release, and the relationship between quantity and intensity potassium in soil were elucidated in reddish paddy soil. Conducting scientific evaluation of soil potassium fertility based on agricultural managment practies and K characteristics of reddish paddy soil, it can be provide the theoretical basis for reasonable and effective applying potassium fertilizer in the reddish paddy soil. The main results were as follows:Contents of total K, slowly available K and available K in the different soil layers under the NPK and NPK+RS treatments are higher than those of counterpart soil layers under the NP and NP+RS treatments. After 54 season rice cropping in 27 years, the soil exchangeable K content in 0-45cm layer was increased with the long-term K fertilization, whereas total K is in deficit state.199.2 K kg/hm2 of chemical potassium fertilizer and 4.2 t/hm2 rice straw (contain 109.2 K kg) was applied into reddish paddy soil with K deficiency under long-term double-crop rice cropping systems, but insufficient to sustain total K pool of the soil; long-term application of 4.2t/hm2 rice straw without applying chemical potassium fertilizer couldn’t maintain the soil K level.There are two different phases in change of nonexchangeable K release of each treatment, i. e., the linear increase in the initial and slow increase in late phase. The accumulations of nonecchangeable K release in the long-term K fertilization (NPK, NP+RS and NPK+RS) treatment were higher than those in treatment with no K fertilizer (CK and NP). The accumulations of nonexchangeable K release were 62.22 mg/kg and 56.12 mg/kg in the treatment with no K fertilizer (CK and NP), while 67.52mg/kg, 64.41mg/kg and 75.33mg/kg with K fertilizer (NPK、NP+RS and NPK+RS) treatments, respectively. The accumulations of nonecchangeable K release in treatments with application of rice straw application (NP+RS and NPK+RS) treatments were significantly higher than those of the treatment with no application of rice straw (NP and NPK), which may promote the change from the part of soil mineral potassium to nonexchangeable K under long-term application of rice straw. The four kinds of kinetic equations (parabolic diffusion equation, zero-order equation, first-order equation and Elovich equation) were tested for their suitability to describe the release of nonexchangeable K from the five different treatments. The kinetics of nonexchangeable K release for five treatments could better be simulated by Elovich equation. Considering release rate and effective of nonexchangeable to plants, the segmented straight line equation are more reliable and more accurate than those of the above four equations.Decomposition of X-ray diffraction pattern showed that clay mineralogy altered with the changes of different fertilization treatments. The illite content in soil was increased by application of K fertilizer and rice straw application on the basis of NP application, while the content of illite in soil was depleted due to long-term no application of K fertilizer. From the change of soil composition, the whole-clay fraction (<5μm) more corresponded more to fertilization treatments than did fine-clay fraction (<1μm) in term of peak area pencentage. Chlorite of mixed-layer illite-chlorite mineral was transformed into free illite and layer illite by long-term fertilization. Applying Potassium and rice straw treatments increased the proportion of poorly crystallized illite (PCI) in free illite. Changes in clay mineralogy were reflected in aspects of K+adsorption caused by long-term K fertilization and rice straw application. Removed soil organic matter [+H2O2] experiment clearly showed that there was a positive effect between soil organic C and the adsorption of K+, especially under low K+concentration. Soil organic C could reduce the K+adsorption of clay minerals under the high K+concentration. The soil minerals were more important than soil organic C in K+absorption. K+adsorption potential was influenced by the composition change of mineral in the long-term fertilization treatment. The significantly correlation between peak area percentage of poorly crystallized illite and K+adsorption potential (M) or adsorption coefficient (K) was observed in the long-term fertilization treatments.After 54 season rice cropping over 27 years period, when added K ranging from 0.4 to 4.0g/L, the rate of K fixation increased with K addition. The values of K fixation capacity were different among five treatments. The K fixation value in the treatments with no application K treatments (CK and NP) was increased compared with initial soil value, while K fixation value in treatments with K application and rice straw application (NPK, NP+RS and NPK+RS) were decreased compared with initial soil value. The results indicated that the mail reason why affecting the increase of K fixation capacity was due to the long-term application of K fertilizer and rice straw, but the capacity of K fixation was relatively lower when application rate K fertilizer was higher. The long-term application of K fertilizer would be lead to K depletion of soil potassium, because a large amount of K was removed by rice crop from the soil under highly intensity rice-rice planting system. A long-term no application of K fertilizer would result in severe K depletion in soil, after that, K was applied into soil, a large amount of K was fixed by the soil, and reduced efficiency of K for crops in season. When the K was relatively higher in soil, it was not easily adsorbed and fixed by the soil. If the K can not be absorbed and utilized by crop in time, it was very likely to leach. After long-term application of K fertilizer and rice straw, the content of available K and slowly available K in soil was increased, and K fixation capacity was decreased. In addition, increasing K+saturation could also result in reduction of soil K fixation capacity under long-term application of K fertilizer and rice straw.Values of-ΔK°and ARek were decreased in the long-term treatments with no K fertilizer, while the value of PBCk was increased. That is, the easy release K become smaller, K adsorption capacity of soil was increased, and K supply capacity of soil reduced. A large number of K application was needed to raise K concentration of soil solution for long-term treatments without K fertilization. Effect of long-term application of rice straw on K behavior was an obvious in the 0-15cm soil layer. K behavior in soil was significantly affected by increasing organic matter and reducing pH value of soil. Through simulaton the equation (PBCk=CEC×KG), the sum of cations extracted BaCL2 or CEC of BaCL2 determination was the best predictive equation of Q/I curve. Organic matter could increase the high-affinity K+sites. The data of this study also proved that the release of a large number of K+into the soil solution was not controlled by K+-Ca2++Mg2+, but was controlled by the K+-NH4+.The average yields of the early rice under the NPK and NPK+RS treatments increased by 15.2% and 10.9%, respectively, and those of the late rice are increased by 17.2% and 9.1% compared with the NP and NP+RS treatments over 27 years. The trends of 27-year yield change in both the early and late rice are different in various treatments. There are negative trends of yield change with time in the CK and NP treatments, while there are the positive trends in the NPK, NP+RS and NPK+RS treatments. Rice straw return into soil increased significantly the rice production. Average rice yield with 27 years rice straw-returned treatment (NP+RS and NPK+RS) was increased by 12.2% and 6.7%, respectively, compared with treatments of NP and NPK application alone. The yield of grain was increased year by year after returning rice straw. Rice straw could partly replace chemical K fertilizer because K brought by rice straw had same nutritional function with that of chemical K fertilizer.更多还原