冻融循环下不同水质对压砂砾石元素淋溶影响

为了了解宁夏地区压砂地在冻融循环作用下,不同水质处理对其元素淋溶释放规律的影响,通过电感耦合等离子体发射光谱仪及电感耦合等离子体质谱仪测定了宁夏中卫市微咸水的元素含量,并通过冻融循环试验探索不同水质对压砂砾石元素淋溶释放的影响,结果表明:当水质相同时,随着冻融循环次数的增加,元素淋溶总量呈增加趋势;当冻融循环次数一定时,蒸馏水处理下的元素淋溶释放总量大于微咸水处理,微咸水在一定程度上抑制冻融循环下的压砂砾石元素淋溶释放.     

不同环境条件下板岩中必需元素的释放规律

利用室内模拟试验研究不同环境条件下板岩必需元素的释放规律,将取自香山地区的灰绿板岩岩样分为蒸馏水干湿循环组(ZLGS)、蒸馏水冻融循环组(ZLDR)和微咸水冻融循环组(WXDR)3组.通过对3组岩样进行50次循环试验,模拟板岩的风化过程.在循环开始前测量板岩基本物理性质并进行SEM微观结构分析;试验过程中定期测量板岩淋溶液电导率EC和淋溶液中必需元素的组成及含量.通过试验研究发现,试验条件下,随着循环次数增加,3种处理的板岩淋溶液EC呈波动增加趋势;3种处理下,必需元素释放种类数排序产生差异,各元素释放量排序以及释放量较大元素种类无差异,必需元素累积释放量按组分排序由大到小为ZLDR,ZLGS,WXDR;必需元素累积释放量与试验循环次数呈对数函数关系.     

覆膜滴灌对玉米田间水热传输及耗水的影响

基于充分滴灌条件下,定量分析了东北典型区玉米膜下滴灌与不覆膜滴灌下太阳净辐射、土壤热通量、土壤温度和作物耗水量的差异.结果表明:在晴天覆膜使得净辐射峰值时间滞后约1 h,在阴天覆膜处理土壤热通量能够为玉米生长提供更多的能量;全生育覆膜与不覆膜处理,冠层上方获得净辐射分别为133.25和135.42 W/m²,覆膜处理获得的可供能量低于不覆膜处理的,但在玉米生长中后期,覆膜处理提高了2%的净辐射;全生育期覆膜提高了0~80 cm土层平均地温1.13 ℃和土壤积温149.68 ℃;覆膜滴灌下玉米生长初期和后期的耗水量显著低于不覆膜滴灌处理下的,全生育期耗水量显著减少10.21%,生育期内平均作物系数K_c显著降低7.42%.     

冷凉地区膜下滴灌大白菜耗水规律及节水潜力

为探索冷凉地区露地大白菜在膜下滴灌条件下的耗水规律与节水潜力,在张家口市灌溉试验站内使用大型称重式蒸渗仪,采用灌水下限指标控制灌水的方法,研究了在膜下滴灌条件下大白菜生育期内蒸发蒸腾与棵间蒸发规律,并通过与常规滴灌和膜孔畦灌的耗水量、产量和水分利用效率等对比,揭示了膜下滴灌在该地区节水增产潜力.结果表明:膜下滴灌大白菜全生育期蒸发蒸腾量214.76 mm,其中:幼苗期、莲座期和结球期蒸腾耗水量分别为14.76,73.56和126.44 mm,日均蒸腾强度为3.64 mm/d;全生育期棵间土壤蒸发量41.10 mm,占总耗水量的19.14%.膜下滴灌相比常规滴灌、膜孔畦灌减少大白菜耗水量14.25,94.17 mm,棵间蒸发与膜孔畦灌相近,相比常规滴灌减少16.18 mm(28.25%),但产量、灌溉水利用效率和水分利用效率可以分别达到80 439.75 kg/hm²,350.24 kg/(hm²·mm),374.56 kg/(hm²·mm),相比常规滴灌提升11 152.65 kg/hm²,18.89 kg/(hm²·mm),72.54 kg/(hm²·mm),相比膜孔畦灌提升14.7 kg/hm²,134.11 kg/(hm²·mm),114.23 kg/(hm²·mm).     

Particle-size effects on soil temperature, evaporation, water use efficiency and watermelon yield in fields mulched with gravel and sand in semi-arid Loess Plateau of northwest China

Gravel and sand mulch is an effective practice in conserving soil and moisture. However, the proportion of different particle size in this kind of mulch layer is an important factor to be considered in order to obtain optimal results from this practice. From 2005 to 2007, a series of experiments including one with watermelon were conducted in the semi-arid Loess Plateau of northwest China to determine the influence of particle size and its proportion in mulch layer on soil temperature, evapotranspiration, water use efficiency (WUE) and watermelon (Citrullus lanatus L.) yield. The treatments in no-watermelon experiments included particle sizes classified as <0.3, 0.3-1, 1-2, 2-4, 4-6, 6-8 and 8-10 cm mesh size or various rates of 2-6 cm pebble accounting for 0, 10, 20, 30, 40, 50, 60 and 70% with 30% 1-2 cm gravel-sand in mulch layer (as well as correspondingly decreasing sand proportions). The watermelon experiment included three particle sizes, 0.3-1, 1-2 and 2-6 cm. Soil temperature at 8:00 h was highest for the 1-2 cm treatment, and the daily average temperature at 14:00 h was highest for the 0.3-1 cm treatment. Soil temperature decreased with particle size increasing due to porosity enlarging. The relationship between soil temperature and particle size followed a quadratic or cubic curve. Soil temperature was increased by gravel-sand mulch plus plastic film. The increment of soil temperature was larger especially for 1-4 cm particle size. In the gravel-sand mulch layer having different size particles, the greater percentage being of 2-6 cm pebbles, increases porosity, and lowers soil temperature, and causes more evaporation. The results of the watermelon experiment showed that soil moisture before seeding would not affect the yield during the years of using gravel mulch. Watermelon yield and WUE were higher for 1-2 and 0.3-1 cm treatments than 2-6 cm treatments in later experiments during 2006 and 2007. In conclusion, 2-6 cm large size particles would not account for much in gravel-sand mulching layer. It would be better if the percentage of 2-6 cm particles was less than 30%.