【作者】 李小坤；

【导师】 吴礼树； 鲁剑巍；

【作者基本信息】 华中农业大学 ， 植物营养学， 2009， 博士

【摘要】 水旱轮作是我国南方主要耕作制度之一,在作物持续增产、维持地力和土壤改良中发挥着重要的作用。水旱轮作区一年两熟或多熟,随作物收获带走大量钾素;同时由于轮作区高温多雨,土壤钾素淋失严重,因此该种植制度下常出现土壤钾素亏缺的现象,并已严重制约着农业生产的发展。在我国钾资源相对短缺的现实条件下,开展水旱轮作条件下的土壤供钾能力研究具有重要意义。本论文采用分室根箱试验,研究了水旱轮作条件下根区与非根区土壤钾素动态变化特征,水旱轮作方式、外源钾、土壤粘土矿物组成与作物吸钾量的相互关系,轮作后的根区与非根区土壤的固钾和释钾规律,以揭示根际土壤供钾特性及对作物生长的意义,从而为不同性质土壤下的水旱轮作制中钾肥的合理施用提供依据。主要研究结果如下:1.土壤样品风干后测定低估了土壤对当季作物的供钾能力。不施钾(-K)条件下,不同含水量时(微湿、近饱和、淹水),红壤、黄褐土、潮土和灰潮土风干样速效钾含量与鲜样测定值相比均有所降低,平均降低幅度分别为11.5%、3.8%、12.1%和5.0%;施钾(+K)条件下,风干样速效钾含量与鲜样测定值相比降幅更大,4种土壤分别为15.1%、9.5%、21.0%和20.2%。-K条件下,红壤、黄褐土、潮土和灰潮土风干样缓效钾含量与鲜样相比也有所降低,平均降低幅度分别为8.7%、13.4%、18.4%和22.8%:+K条件下,红壤风干样缓效钾含量与鲜样相比显著增加,平均增幅为34.7%。黄褐土、潮土和灰潮土风干样缓效钾含量与鲜样相比则有所降低,平均降幅分别为8.7%、7.7%和9.9%。试验结果还显示,采用鲜样直接测定土壤速效钾和缓效钾时,同一土壤不同含水量间的钾素含量无显著差异。2.无论种植油菜还是水稻,作物吸收利用的钾主要来自于根区。根区钾含量降低时,非根区土壤钾向根区迁移。黄红壤非根区土壤水溶性钾和交换性钾含量(v)与距根区距离(x)线性拟合达显著相关,距根区越近,含量越小;黄褐土各形态钾素含量与距离的相关性不显著。3.水旱轮作条件下,作物首先吸收利用根区土壤水溶性钾,随着作物生长和吸钾强度的增大,根区土壤交换性钾和非交换性钾向水溶性钾转化。同时,非根区土壤水溶性钾向根区迁移;非根区交换性钾和非交换性钾向水溶性钾方向转化,也有一定程度降低,距根区越近对作物吸钾量贡献越大。一个水旱轮作期内,黄红壤主要供钾形态为交换性钾和水溶性钾,作物吸收利用的非交换性钾较少;黄褐土主要供钾形态为非交换性钾,其次是交换性钾和水溶性钾。4.油菜—水稻轮作(先旱后水)条件下,无论黄红壤还是黄褐土,施钾对前季作物油菜干物质量没有明显影响,但能显著提高轮作后季水稻干物质量。水稻—油菜轮作(先水后旱)条件下,对于黄红壤,施钾对前、后季作物干物质量均没有明显影响;而在黄褐土上,施钾对前季作物水稻增产显著。无论是先旱后水,还是先水后旱,施钾均可明显提高作物非籽粒部位的钾含量,且黄红壤上种植作物的各部位钾含量明显比黄褐土上的高。整个轮作期,+K处理作物吸钾量与-K处理相比显著提高。两种轮作方式下,黄红壤上种植作物的吸钾量明显高于黄褐土。5.水旱轮作条件下,外源钾的施用可以明显提高根区与非根区土壤各形态钾素含量。外源钾施入黄红壤后主要以水溶态和交换态钾存在,施入黄褐土后主要以交换态和非交换态钾存在。由于作物生长吸钾,根区土壤钾素与不种作物处理相比显著降低,施钾可以缓解根区土壤钾素的亏缺,并显著提高非根区土壤钾素含量,且当季施钾处理的效果更加明显。不同水旱轮作方式下,施钾对根区与非根区土壤钾素动态变化的影响不尽相同。6.水旱轮作条件下,作物生长吸钾改变了土壤粘土矿物组分。与基础土壤相比,轮作后黄红壤不施钾处理根区土壤绿泥石含量增加;黄褐土不施钾处理根区土壤蛭石、绿泥石和1.4 nm过度矿物均相对增加。距根区较近的非根区土壤粘土矿物组分也有相应改变。外源钾的施用在一定程度上缓解了土壤粘土矿物组分的变化。7.水旱轮作后,根区与非根区土壤的固钾和释钾能力不同。以1:1型高岭石为主要粘土矿物的黄红壤固钾能力较弱。以2:1型水云母和蛭石为主要粘土矿物的黄褐土固钾能力较强,且固钾量随着外源钾加入浓度的增加而增大。根区土壤固钾能力显著高于非根区土壤,释钾量则相反。土壤非交换性钾含量也是影响土壤钾素固定和释放能力的因素之一。外源钾的施用降低了土壤的固钾率,提高了轮作后土壤的供钾能力。更多还原

【Abstract】 Paddy-upland rotation is one of the dominant cropping systems in the southern regions of China, which plays an important role in increasing crops yield, maintaining soil fertility and ameliorating soil. Soil potassium (K) deficiency in paddy fields is becoming one of the key limiting factors for sustainable agricultural production because of crops’ removing enormous amounts of K and K leaching in the high temperature and rainy rotation regions. Therefore, it has important significance to carry out research works on K-supplying capacity in soils under the condition of being short of potash resources in China. This paper studied the dynamics of soil K in root zone and non-root zone under paddy-upland rotation, the relation of paddy-upland rotation patterns, external K, soil clay minerals and K uptake by crops, and the characteristics of K fixation-release in root-zone and non-root-zone soils after rotation using a rhizobox system. The special purpose was to find out the characteristics of soil K-supplying capacity in rhizosphere soil and provide evidence for reasonable application of K fertilizer in paddy-upland rotation system. The main results were as follows:1. It underestimated the soil K-supplying capacity to seasonal crop when soil samples were determined by air-drying. Air-dried soil available K concentration of red soil (RS), yellow cinnamon soil (YCS), fluvo-aquic soil (FAS) and grey fluvo-aquic soil (GFAS) decreased averagely by 11.5%, 3.8%, 12.1% and 5.0% respectively compared with that of fresh soil in different soil water content (slightly wet, close by saturation, waterlogging) in the treatment without K fertilizer (-K). In the treatment with K fertilizer (+K), the decrease of soil available K was greater, and four soils were 15.1%, 9.5%, 21.0% and 20.2%, respectively. Air-dried soil slowly available K concentration of RS, YCS, FAS and GFAS decreased averagely by 8.7%, 13.4%, 18.4% and 22.8% respectively compared with that of fresh soil in the -K treatment. In the +K treatment, air-dried soil slowly available K concentration of RS increased by 34.7% significantly compared with that of fresh soil, but that of YCS, FAS and GFAS decreased by 8.7%, 7.7% and 9.9%, respectively. It was also indicated that there was no significant difference in K concentration for the same soil with different water content when determined in fresh soil sample.2. Potassium uptake by crops mainly came from root zone irrespective of planting rapeseed or rice. Soil K in non-root zone transferred towards root zone when soil K concentration in root zone decreased. A significant positive linear relationship was observed between yellowish red soil (YRS) water soluble K and exchangeable K in non-root zone (y) and the distance to the root zone (x). The closer to the root zone, the concentration of soil K was lower. There was no significant linear relationship between soil K concentration and the distance to root zone in YCS.3. Under paddy-upland rotation, soil water soluble K in root zone was reduced first. Along with plants’ growing and K uptake, soil exchangeable K and non-exchangeable K in root zone were transformed into water soluble K, thus decreasing gradually. Soil water soluble K in the non-root zone were moving towards the root zone, and exchangeable K and non-exchangeable K were transformed into water soluble K. The closer to the root zone, the greater the contribution to K uptake by plants. Within one rotation cycle, YRS exchangeable K and water soluble K were the main forms of potassium available to the plants, and little non-exchangeable K could be absorbed. For YCS, the main form of potassium available to the plants was non-exchangeable K, followed by exchangeable K and water soluble K.4. Potassium fertilizer application had no significant effect on the dry matter yield of rapeseed, but improved that of rice significantly with rapeseed-rice rotation (first upland and then paddy) no matter whether yellowish red soil (YRS) or yellow cinnamon soil (YCS). For rice-rapeseed rotation (first paddy and then upland), K fertilizer had no obvious effect on the dry matter yield of rice and rapeseed in YRS, but could improve that of rice in YCS significantly. Applying K fertilizer could improve K concentration of crops significantly except seed. K concentration of crops in YRS was higher than that in YCS. In the whole rotation, K uptake by crops in the +K treatment increased significantly compared to that in the -K treatment. K uptake by crops in YRS was higher than that in YCS under the two rotation patterns.5. Application of external K could improve the concentrations of different forms of K in root-zone and non-root-zone soils significantly. Applied external K mainly existed in water soluble K and exchangeable K in YRS, and in exchangeable K and non-exchangeable K in YCS. Soil K decreased significantly due to K uptake by crops, compared to that in the treatment without crops. K fertilizer application could alleviate soil K deficiency in the root zone, and improve soil K concentration in non-root zone significantly. The effects of K fertilizer application on the dynamics of soil K in root zone and non-root zone were not the same in different patterns of paddy-upland rotation. 6. Potassium uptake by crops changed the soil clay mineral under paddy-upland rotation. For YRS, the content of chlorite was increased in root-zone soil in the -K treatment. For YCS, the contents of vermiculite, chlorite and 1.4 nm intergrade minerals were all increased in the root-zone soil in the -K treatment. Soil clay minerals in non-root zone closer to root zone were also changed. External K application alleviated the changes of soil clay minerals to some extent.7. It differed in K fixation and release capacity between root-zone and non-root-zone soil after paddy-upland rotation. The capacity of K fixation was weak for YRS which is rich in 1:1 clay mineral such as kaolinite. But the capacity of K fixation was strong for YCS which is rich in 2:1 clay mineral such as hydromica and vermiculite. And the amount of K fixed in YCS increased with increase in the amount of added K. Root-zone soil had more K fixation and less K release than the non-root-zone soil. The concentration of non-exchangeable K was one of the factors which affected K fixation and release in soil. External K application decreased the percentage of K fixed and improved the K-supplying power of soil.更多还原