Evapotranspiration and crop coefficient of spring maize with plastic mulch using eddy covariance in northwest China

Spring maize under plastic mulch is the staple food crop in northwest China. Studying its evapotranspiration (ET) and crop coefficient (K_c) is important for managing water-saving irrigation in the region. Eddy covariance (EC) was applied to measure spring maize ET in 2007 in northwest China, focusing on the characteristics of the maize ET and K_c processes under plastic mulch. An interesting result was that a higher K_c in this study relative to the value of FAO 56 was presented in the mid and late season, e.g. average K_c was 1.46, 1.39 and 1.22 during the heading, filling and maturity stage, respectively. This result was mainly due to that (1) the plastic mulch had an effect on anti-senescence of maize and great green leaf still existed before the harvest; (2) the FAO 56 PM model may underestimate the reference crop ET in the mid and late season of maize in the region; (3) the planting density was higher in the study, which was about 374,800 plants ha⁻¹. Though K_c during the mid and late season was high, a high water use efficiency of 25.2 kg ha⁻¹ mm⁻¹ was still obtained in the study. Our study confirmed that plastic mulch has beneficial effect on improving maize water use efficiency in this severe water shortage region of northwest China.     

砂石覆盖厚度和粒径对土壤蒸发的影响

在干旱半干旱地区,砂石覆盖作为一项传统的覆盖技术,可以明显减少土壤蒸发,为作物生长提供良好的水分条件。为研究不同粒径和厚度砂石覆盖对土壤蒸发的影响,进行了室内模拟试验,对3种粒径(2.5~10、10~25和25~40 mm)和2种覆盖厚度(8 cm和14 cm)以及不同粒径砂石配比条件下土壤水分蒸发进行了研究。结果表明,砂石覆盖能有效地抑制土壤蒸发,在土壤含水量较高的阶段,这种抑制作用更加明显。砂石覆盖对土壤蒸发的抑制作用与粒径和覆盖厚度密切相关,在2.5~40 mm粒径范围内,随着砂石粒径的增大,砂石覆盖对蒸发的抑制作用降低,对蒸发过程的影响减弱,覆盖厚度越大,蒸发量越小。有效的砂石配比应选择细砂石处理,不宜过粗。     

膜上灌春小麦调亏效应研究

在膜上灌水方式下覆膜和露地处理全生育期不同水分处理调亏下,膜上灌高产处理耗水量比对照减少了310.3mm却增产1363.69kg/hm2,同一水分处理下膜上灌丰水处理F(FM)比露地丰水处理F(B)增产40.99%,WUE提高了4.67kg/(mm.hm2);膜上灌中度处理M(FM)比露地中度处理M(B)增产52.55%,WUE提高了6.86kg/(mm.hm2)。相同水分条件下覆膜处理具有明显的增温、保墒增产作用,最高产量所需的土壤适宜水分下限较露地下降10%~15%。结果表明同一水分处理下覆膜小麦不仅具有较高的生物产量,而且具有较大的库容,因而开花后干物质积累量,茎、叶器官的输出率、分配率、转换率均高于露地小麦,最终表现为粒重增加经济产量提高。     

南疆膜下滴灌棉田土壤温度时空变化规律研究

为了研究南疆免冬春灌“干播湿出”膜下滴灌棉花生育期土壤温度时空变化特征,测定了棉花宽行、窄行和膜间不同深度(地表下5、10、15、20、30、40、60 cm)土壤温度的变化情况。试验结果表明:浅层土壤温度受气温影响变化剧烈程度高于深层,太阳辐射变化对40 cm以下土壤温度日变化影响微弱,地膜覆盖可明显提高棉花播种-出苗阶段浅层土壤温度,具有增温效应,增温效应为宽行窄行膜间;蕾期和花铃期具有平抑土壤温度变化的作用;而在吐絮期后地膜覆盖出现保温效应。各层土壤日均地温均与气温呈线性关系。     

不同水分胁迫和覆盖方式对番茄产量和水分利用效率的影响

通过田间试验,研究了不同水分胁迫和覆盖方式对番茄产量和水分利用效率的影响。结果表明,轻度水分胁迫下果实产量为36.3×10~3 kg/hm~2,中度和高度水分胁迫下,果实产量相较于轻度水分胁迫分别减少了11.3%和31.7%;秸秆覆盖和地膜覆盖比无覆盖条件下果实产量分别增加25.3%和16.5%。秸秆覆盖条件下,水分利用效率、净蒸散利用效率及灌溉水利用效率最高,分别为19.7、47.5和16.7kg/m~3,地膜覆盖条件下则略为低一些,无覆盖条件下最低。针对最大水分利用效率和最大产量的耗水量临界值,相较于无覆盖和地膜覆盖,秸秆覆盖条件下临界值差别最小为60mm。不同水分胁迫下秸秆覆盖方式可明显改善土壤的水分状况,促进番茄生长,显著提高作物产量和水分利用效率。     

基于CAN总线的触摸式滴灌控制软件设计

为了适应新疆生产建设兵团棉花膜下滴灌控制的需要,设计了基于现场CAN总线的膜下滴灌控制系统.为此,在对一种CAN总线控制系统做简要介绍的前提下,设计了该系统软件的功能模块,包括节点控制器地址编码、阀门轮灌编组设定、阀门控制操作、阀门控制器状态显示、故障报警指示、数据库记录及用户管理等.尤其对核心功能模块(如地址编码、阀门编组等)给出了详细的设计思路和注意事项.设计的软件具有界面美观、触摸式操作、使用简单等特点,符合农场职工的操作需要.     

秸秆覆盖对桃树地植-土环境变化的影响研究

对果园实施秸秆覆盖,短期内主要表现为保墒和调节土壤温度两大功效.研究在桃树果园实施秸秆覆盖3年以来对植物与土壤环境的影响,主要从地上部分桃树形态变化、地下部分根系生长变化、土壤养分与土壤微生物变化这几个方面将覆盖与对照进行对比分析.分析表明,覆盖比对照树冠体积、茎干断面、根系直径小于1 cm的总长分别增加33.9%、110.6%和115.69%,同时使土壤养分和微生物也发生很大变化,分别是对照硝态氮含量、真菌、细菌和放线菌含量的2.2倍、1.56倍、2.36倍和1.89倍.所以长期实施秸秆覆盖对植物生长和土壤环境的改善有着很大的积极作用.     

纸膜与水田泥浆粘附特性的测量方法探讨

为了保证覆膜机构的覆膜质量,有必要研究纸膜与水田泥浆的粘附特性。在对土壤与触土部件的粘附理论与测量装置研究的基础上,提出基于电子万能试验机进行纸膜与水田泥浆粘附性的测量方法。研究表明,纸膜与泥浆的粘附力的大小对覆膜质量有重要影响。     

梳穗联合收获机禾秆处理装置的试验研究

收获后田间直立禾秆的处理问题是梳穗联合收获机实现产业化的瓶颈，通过对梳穗联合收获机禾秆处理装置的试验分析，得出了禾秆切碎器的锤片排列形式及工作腔间隙、锤片线速度等主要工作参数计算模型，解决了现有梳穗联合收获机对作物适应性较差及2m以上宽割幅发展的难题。     

Mulch resistance to water vapor transport

Mulches augment soil moisture availability to plants by restraining direct evaporation of soil water. Yet, in field conditions wind decreases their resistance to water vapor transport, diminishing their efficiency as a water conservation measure. The relation between vapor transport resistance and wind speed was investigated in a wind tunnel where air flow was turbulent. The mulch material was chopped straw with bulk densities of 31 and 37 kg m⁻³, and chemically stabilized aggregates segregated in diameter classes 1-2, 2-4, 4-8, 8-11.2 mm, in layers 10-100 mm thick. The resistance decreased exponentially with increasing wind speed from the molecular diffusion value at zero wind speed, suggesting that turbulence penetrates the pores of the mulch and drives convective water vapor transport. Resistance rose exponentially with increasing layer thickness, a mirror reflection of the turbulence decay profile. Higher bulk density of the straw and finer aggregates augmented the resistance. The convective component of the vapor transport resistance was related to mulch area index, defined as the surface area of the solid elements of mulch per unit covered ground area. This procedure merged the effect of layer thickness and that of straw bulk density or aggregates size into a single function, indicating that friction forces proportional to internal area of the solid fabric restrain the penetration of momentum in the porous medium. Two-layered mulches combining straw and aggregates have a higher resistance than the sum of the resistances of the individual components as is expected from the attenuation of convection in the top layer. The functions derived in this study can serve as input for models evaluating the impact of mulches on soil water balance.