Effects of Straw Covering and Different Types of Potassium Fertilizer on Salinity Accumulation in Surface Layer of Tobacco-planted Paddy Soil

[Objective] This study aimed to investigation the effects of straw covering and different types of potassium fertilizer on salinity accumulation in surface layer of tobacco-planted paddy soil in southern China. [Method] Tobacco variety ‘Yunyan87’ was used as the experimental material to investigate the effects of salinity accumulation in surface layer of tobacco-planted paddy soil on the growth and development of flue-cured tobacco using different types of potassium fertilizer and mulching cultivation methods. [Result] The results showed that K＋ , Ca2＋ , SO42and NO3-were the major salt ions in topsoil at different growth stages of flue-cured tobacco, Na ＋ and Mg2＋ contents were also relatively high at vigorous growth stage, indicating that these salt ions were easily accumulated in surface layer of soil; to be specific, the absolute increase of salt ion concentration showed a decreasing order of K＋ SO42- NO3-Ca2＋ Mg2＋ Na＋ Cl-, while the relative increase of salt ion concentration showed a decreasing order of Ca2＋ K＋ Na＋ NO3-SO42-Mg2＋ Cl-. At 60 d posttransplanting, total salt content in topsoil reached the minimum of 359.1 mg/kg in Treatment 2, total salt content in topsoil reached the maximum of 536.1 mg/kg in Treatment 5 （CK）, which was significantly higher than that in other treatments. At 90 d post-transplanting, no significant difference was observed in total salt content among various treatments. At harvesting period, total salt content in topsoil reached the maximum of 3 278.4 mg/kg in Treatment 1, which was significantly higher than that in other treatments. Topsoil pH showed no significant differences among various treatments at three different periods, ranging from 5.39 to 5.59. Straw covering could effectively reduce salt content in topsoil, accelerate vigorous growth of tobacco, shorten vigorous growth period and increase plant height, leaf number and lead area; at vigorous growth stage, root vitality and root volume of tobacco were improved, but the yield and output value were relatively low. Major agronomic traits and yield of tobacco showed no significant difference among various treatments. Output value of tobacco reached the maximum of 24 196.8 yuan/hm2 in Treatment 3, which was significantly higher than that in other treatments. [Conclusion] Appropriate types and proportions of potassium fertilizer and straw covering can effectively reduce the total salt content in tobacco-planted paddy soil and increase the effective supply amount of K＋ , Ca2＋ , SO42-and NO3-, thereby promoting and improving the root vitality of tobacco, which is conducive to the growth and development of tobacco and will eventually enhance the yield, quality and economic benefits of flue-cured tobacco.

秸秆覆盖量对夏玉米产量影响的试验研究

通过对夏玉米在露天和干旱棚控水2种土壤水分状况下生长状况的观测,发现秸秆覆盖夏玉米有明显增产效应,作物水分利用效率均得到了不同程度提高。通过对0、3000、6000、9000、12000 kg/hm2五种处理下玉米状况的对比,得出6000 kg/hm2为渭河平原地区最适宜夏玉米田秸秆覆盖量。在6000 kg/hm2覆盖量下,露天小区夏玉米可增产5.61%。试验证明,渭河平原地区秸秆覆盖夏玉米,增产潜力大,是一种值得推广的玉米增产措施。

覆草量对水盐运动影响的实验研究

利用盆钵土壤自动供水装置，定量研究了稻草不同覆盖量对滨海盐土水盐运动的影响。结果表明；覆草量与盆钵土壤日均蒸发量、节水量及表层０～５ｃｍ土层含水量和含盐量有一定的定量关系；覆草的节水和抑盐效果分别为每增加０．１ｋｇ·ｍ－２的覆草量，抑制蒸发率提高５．９２％和抑盐率提高２．５７％。

Effects of key design parameters of tine furrow opener on soil seedbed properties

The structural parameters of tine furrow openers have significant effects on soil property of seed furrow in no-till planting,thereby affecting crop growth and yields.In order to analyze the effects of key parameters of tine furrow openers on soil properties(soil bulk density,soil water-stable aggregates(WSA),and soil disturbance)of the surface soil layer of 0-10 cm and surface straw disturbance,the tine furrow openers with different structural parameters,including cutting edge thickness,cutting edge curve,penetration clearance angle and rake angle,were designed and tested under no-till conditions.Orthogonal test and single factor test were performed to analyze the effects of different parameters.Results showed that the rake angle,cutting edge thickness and cutting edge curve had significant effects on cross-sectional area of furrow(Af)and disturbance of surface straw;the rake angle had a significant effect on soil bulk density.Soil types and operating depth had significant effects on soil disturbance caused by tine furrow openers.The concave type tine furrow opener produced the lowest soil disturbance and soil bulk density of seed furrow,the highest surface straw disturbance and the greatest content of WSA(>0.5 mm).With increasing rake angles of tine furrow opener,the width of seedbed(Wsb)and the Af decreased first and then increased,respectively,while the width of soil throw(Wst)and the height of ridge(Hr)increased.The Wsb and Af created by tine furrow opener with 60°rake angle were significantly lower than that with others,respectively.The tine furrow opener with rake angle ranged from 45°to 60°created the lowest soil bulk density.As the penetration clearance angle increased,the content of WSA(>0.5 mm)decreased,but the effect of penetration clearance angle on the content of WSA(<0.5 mm)was not significant.The cutting edge thickness(<2 mm)had no significant effects on soil properties of seedbed.This study could provide a reference for optimal design of the tine furrow opener to create more suitable seedbed environment,and promote the application of the light no-till planters.