Effects of gravel mulch on aeolian transport:a field wind tunnel simulation

The shape,size and coverage of gravels have significant impacts on aeolian sand transport.This study provided an understanding of aeolian transport over the gravel mulching surfaces at different wind velocities by means of a mobile wind tunnel simulation.The tested gravel coverage increased from 5% to 80%,with a progressive increment of 5%.The gravels used in the experiments have three sizes in diameter.Wind velocities were measured using 10 sand-proof pitot-static probes,and mean velocity fields were obtained and discussed.The results showed that mean velocity fields obtained over different gravel mulches were similar.The analysis of wind speed patterns revealed an inherent link between gravel mulches and mean airflow characteristics on the gravel surfaces.The optimal gravel coverage is considered to be the critical level above or below which aeolian transport characteristics differ strongly.According to the present study,the optimal gravel coverage was found to be around 30% or 40%.Threshold velocity linearly increased with gravel coverage.Sand transport rate first increased with height above the wind tunnel floor（Hf）,reaching a peak at some midpoint,and then decreased.

Effects of Different Gravel Mulched Years on Soil Microbial Flora and Physical and Chemical Properties in Gravelsand Mulched Fields

Soil microbial flora and influencing factors of soil microbes in soil and gravel-sand mixed layer（ SGSML）,roots denseness layer（ RDL）,eluviate layer（ EL） and calcium accumulation layer（ CAL） in gravel-sand mulched fields（ GSMFs） with different gravel mulched years（ 1,6,12,19 and 25 years） were studied. The results showed that in the composition of soil microbes in the GSMFs,the quantity of bacteria was the largest,followed by actinomycetes,while the number of fungi was the smallest. The total quantity of soil microorganisms in the GSMFs dropped rapidly with the increase of soil depth,which was related to the sudden decrease in the quantity of bacteria. The number of microbes in the RDL was larger than that in the SGSML with few roots due to the effects of root distribution. The number of bacteria and actinomycete in the growing season was larger than that in the non-growing season,while the quantity of fungi in the growing season was smaller than that in the non-growing season. The quantity of bacteria and fungi was the largest in the GSMFs which had been mulched with gravel for 6-12 years. With the increase of mulching time,the GSMFs aged gradually,so their quantity reduced gradually. The quantity of actinomycetes was the smallest in the GSMFs which had been mulched with gravel for 6-12 years and increased with the increase of mulching time. The number of soil microbes in the GSMFs had a good correlation with soil moisture content,p H and mulching time. Soil total carbon content was an important factor restricting the quantity of soil microbes in the GSMFs.

Effects of Different Gravel Mulching on Soil Moisture Status and Regression Model Prediction in Arid Regions

Drought is one of the main factors limiting the agricultural planting and production;gravel mulching is an effective inhibiting evaporation and water-saving planting pattern in the arid regions. In this study, experiments were conducted to study soil moisture effect and regression model with different gravel mulching, the soil moisture content and evaporation were compared that gravel mulched with different particle sizes, different thickness layer and different mulched years. The results showed that: 1) The cumulative soil evaporation of gravel mulched was only 29.3% of that bare fields. Mulching gravel could significantly reduce soil moisture evaporation. 2) The effects of inhibiting soil moisture evaporation are the best when mulch gravel thickness is 10 - 15 cm. 3) The particle size of gravel mulched is smaller, the evaporation inhibition effect will be better. Considering the water holding capacity and material economy, it is the most suitable to mulch gravel with the particle size of 3 - 5 cm. 4) Mulching gravel on the soil surface for 1 - 3 years can improve the soil moisture content. However, the gravel was mulched for more than five years, the soil moisture content decreased significantly. 5) The quadratic polynomial regression fitting model can better simulate and predict the cumulative evaporation on different gravel mulched, and the regression fitting degree R2 is more than 0.98.

Long-term effects of gravel―sand mulch on soil organic carbon and nitrogen in the Loess Plateau of northwestern China

Gravel-sand mulch has been used for centuries to conserve water in the Loess Plateau of north- western China. In this study, we assessed the influence of long-term （1996-2012） gravel-sand mulching of cultiv- ated soils on total organic carbon （TOC）, light fraction organic carbon （LFOC）, microbial biomass carbon （MBC）, total organic nitrogen （TON）, particulate organic carbon （POC）, mineral-associated organic carbon （MOC）, perma- nganate-oxidizable carbon （KMnO4-C）, and non-KMnO4-C at 0-60 cm depths. Mulching durations were 7, 11 and 16 years, with a non-mulched control. Compared to the control, there was no significant and consistently positive effect of the mulch on TOC, POC, MOC, KMnO4-C and non-KMnO4-C before 11 years of mulching, and these organic C fractions generally decreased significantly by 16 years. LFOC, TON and MBC to at a 0-20 cm depth in- creased with increasing mulching duration until 11 years, and then these fractions decreased significantly between 11 and 16 years, reaching values comparable to or lower than those in the control. KMnO4-C was most strongly correlated with the labile soil C fractions. Our findings suggest that although gravel-sand mulch may conserve soil moisture, it may also lead to long-term decreases in labile soil organic C fractions and total organic N in the study area. The addition of manure or composted manure would be a good choice to reverse the soil deterioration that occurs after 11 years by increasing the inputs of organic matter.

Response of Watermelon to Gravel-Mulch and Supplementary Irrigation: Yield, Water Use Efficiency and Root Distribution

A field experiment was conducted to investigate the effect of supplementary irrigation on watermelon (Citullus lanatus) yield, water-use efficiency (WUE) and root distribution in gravel-mulched field in northwest Loess Plateau, China, during 2001 and 2002 growing seasons. The results showed that gravel mulch significantly improved seedling emergence, increased yield and WUE, and alleviated the influence of drought on plant growth. Regardless of gravel mulch application, supplementary irrigation increased watermelon yields, average fruit weight and number of fruit, especially yield increased as the amount of irrigation increased (P<0.05). Generally, WUE of irrigated treatments were higher than that of non-irrigation treatment in gravel-mulched field. The effect of water supply on root distribution was different in two years. In 2001, average root length density (RLD) and root weight density (RWD) whole the soil profile increased. In 2002, however, RLD and RWD decreased as water supply increased. The average RLD and RWD in 2001 were significantly higher than those in 2002. Maybe we can interpret the phenomenon with the theory that there is a need to optimize root distribution (in terms of water relations) and aboveground biomass for a given water supply.The yield may not depend as much on root growth as on the amount of water required at critical stages. A significant effect of soil depth on RLD and RWD were observed in both years, but did not rapidly decrease with depth.

Information Technology Research on Productivity Evaluation of Gravel-mulched Field in Ningxia

The evaluation process of traditional land productivity is relatively complex,and the evaluation indices and results cannot display visually.With the development of geographic information system science,there are more and more studies on the GIS-based land productivity evaluation.GIS system can combine the evaluation model with information system software,realizing the visual display of all the evaluation factors.In this paper,with the development process of GIS-based management information system as references,the management information system for GIS-based gravel-mulched field productivity evaluation was designed and developed by combining with the SI model for gravel-mulched field productivity evaluation.The system was developed under VB environment,integrated with MapInfo,and the evaluation results could be shown visually in the system windows.

Long-term effects of gravel-sand mulch thickness on soil microbes and enzyme activities in semi-arid Loess Plateau,Northwest China

In semi-arid areas of China,gravel and sand mulch is a farming technique with a long history.In this study,a sample survey was conducted on long term gravel sand mulch observational fields in the Northwest Loess Plateau to determine the effects of long term mulch on soil microbial and soil enzyme activities.We found that after long term gravel-sand mulch,compared with bare ground,soil organic matter,alkali nitrogen,conductivity decreased,while pH and soil moisture increased.Urease,saccharase and catalase decreased with increased mulch thickness,while alkaline phosphatase was reversed.The results of Illumina MiSeq sequencing shows that after gravel-sand mulch,the bacterial and fungal community structure was different from bare land,and the diversity was reduced.Compared with bare land,the bacteria Proteobacteria and Acidobacteria abundance increased with increased thickness,and Actinobacteria was opposite.Also,at the fungal genus level,Fusarium abundance was significantly reduced,and Remersonia was significantly increased,compared with bare land.Redundancy analysis(RDA)revealed that soil environmental factors were important drivers of bacterial community changes.Overall,this study revealed some of the reasons for soil degradation after long term gravel-sand mulch.Therefore,it is recommended that the addition of exogenous soil nutrients after long term gravel-sand can help improve soil quality.

砾石覆盖下的农田土壤环境效应:研究进展与展望

砾石覆盖是旱区特有的一种保护性耕作模式。长期的农业生产实践已经证明,地表覆砂能够很好地适应旱区严酷、恶劣的自然环境,并为当地农业发展和效益提升带来极大助力。然而,砾石覆盖农田退化所带来的一系列负面效应愈加凸显,成为当地农业发展的障碍因子。文章以砾石覆盖的土壤环境效应为脉络,归纳总结了砾石覆盖对土壤水热环境、土壤盐分、土壤有机质、土壤微生物和酶活性,以及水土保持等方面的影响效应和相关机制。同时,进一步指明旱区砂田当前所面临的问题与挑战,并提出该领域未来可持续深化和拓展的方向,主要包括:(1)砾石覆盖农田退化过程中土壤环境的综合演变机制;(2)“砾石-土壤-作物”系统间的协同作用机制;(3)应对砂田退化的农业修复模式及可持续发展路径;(4)砾石覆盖对局部区域气候的影响机制。

旱区连作砂田土壤质量和土地生产力演变与调控研究进展

砾石覆盖在改变旱区水文循环和物质转化方面有着至关重要的作用。然而,长期连作给砂田土壤质量及土地生产力带来危机和不确定性。以连作砂田为研究对象,归纳总结了连作年限对砂层质地结构、土壤物理结构、土壤水盐热效应、土壤养分状况、土壤酶活性、土壤微生物特性、作物生长发育以及产量品质的影响效应和可能机制,发现砂田土壤生态环境和土地生产力在人类活动及自然侵蚀的扰动和破坏下整体呈现退化态势,但对不同覆盖条件、施肥水平和种植结构等农田管理措施的响应过程表现出差异性。继而,基于土壤质量和土地生产力的协同和互作效应深入揭示了砂田性能逐年退化机理,并简述了生物、农业及工程调控措施在砂田退化阻控和修复方面的应用进展。在此基础上,提出了砂田退化进程中急需解决的关键科学问题和未来发展方向,主要包括土壤质量演变的基本过程及其发生机制、“砾石-土壤-微生物-植物”系统的叠加和互作效应及其分子机理、土壤改良与生物防治措施的定量化及其调控机制三个方面。在气候变化、植被演替和土地退化背景下,废弃风化砾石的劣化增肥机制及其环境效应将是今后研究的重点。

Soil mulching can mitigate soil water defi ciency impacts on rainfed maize production in semiarid environments

Temporally irregular rainfall distribution and inefficient rainwater management create severe constraints on crop production in rainfed semiarid areas. Gravel and plastic film mulching are effective methods for improving agricultural productivity and water utilization. However, the effects of these mulching practices on soil water supply and plant water use associated with crop yield are not well understood. A 3-yr study was conducted to analyze the occurrence and distribution of dry spells in a semiarid region of Northwest China and to evaluate the effects of non-mulching （CK）, gravel mulching （GM） and plastic film mulching （FM） on the soil water supply, plant water use and maize （Zea mays L.） grain yield. Rainfall analysis showed that dry spells of ≥5 days occurred frequently in each of 3 yr, accounting for 59.9-69.2% of the maize growing periods. The 〉15-d dry spells during the jointing stage would expose maize plants to particularly severe water stress. Compared with the CK treatment, both the GM and FM treatments markedly increased soil water storage during the early growing season. In general, the total evapotranspiration （ET） was not significantly different among the three treatments, but the mulched treatments significantly increased the ratio of pre- to post-silking ET, which was closely associated with yield improvement. As a result, the grain yield significantly increased by 17.1, 70.3 and 16.7% for the GM treatment and by 28.3, 87.6 and 38.2% for the FM treatment in 2010, 2011 and 2012, respectively, compared with the CK treatment. It＇s concluded that both GM and FM are effective strategies for mitigating the impacts of water deficit and improving maize production in semiarid areas. However. FM is more effective than GM.

砂石与秸秆覆盖对风沙土水分蒸发特性的影响

探究不同厚度的砂石和秸秆覆盖对辽西北风沙土土壤水分蒸发的影响机理,特别是在不同初始含水率下的影响,并探索抑制辽西北风沙地土壤水分蒸发的最佳模式,也为风沙区植被建设提供理论基础。首次以辽西北风沙土为研究对象,运用自行设计的蒸发桶进行为期20天的室内蒸发模拟试验,研究土壤蒸发量随蒸发时间的变化规律。结果表明,砂石与秸秆覆盖能够抑制土壤水分蒸发,随着初始含水率增大,砂石与秸秆覆盖厚度越厚,其保持土壤水分的效果就越强。

不同大果型西瓜品种砂田农艺性状及丰产性鉴定

为增强压砂西瓜产业活力,筛选出在砂田种植条件下具备发展潜力的大果型西瓜品种,在宁夏压砂西瓜核心产区对选取的8个大果型西瓜品种,从生长势、抗病性、果实性状和产量等方面综合分析了各品种的特征特性。结果表明,供试品种1912主蔓长、节间长优势较高,蔓粗最粗,枯萎病、霜霉病、白粉病和炭疽病发病率均为最低,抗病性表现最优,综合表现突出。该品种果实横径最大,为245.80 mm;果实纵径较大,为333.90 mm;果实中心糖度、边缘糖度均为最高,分别为12.80%、9.60%;单瓜质量最高,为9.04 kg,较对照品种金城红金五高0.53 kg;商品率较高,为91.33%;西瓜折合产量和商品瓜折合产量也最高,分别为31391.20、28669.58 kg/hm^(2),较对照品种金城红金五分别增产6.24%、5.47%。综合以上各项性状表现,认为1912种植优势突出,适宜在砂田种植模式进一步推广。

微咸水补灌年限对压砂地水盐分布及西瓜产量和品质的影响

【目的】探讨微咸水补灌年限对压砂地土壤水盐分布特征及西瓜产量和品质的影响。【方法】采用田间定位调查方法,研究了微咸水补灌年限为2、4、7、10、14 a的压砂地0~60 cm土壤水盐动态分布及西瓜产量和品质。【结果】西瓜伸蔓期和收获期土壤饱和电导率随微咸水补灌年限增加而增加,荒地土壤20~40 cm土层饱和电导率最高,而压砂地在40~60 cm土层饱和电导率最高;微咸水补灌增加了开花坐瓜期土壤体积含水率,但随微咸水补灌年限增加呈先增加后减小的趋势;压砂地表层(0~10 cm)土壤体积含水率最高,而荒地10~20 cm土层的土壤体积含水率最高;与荒地相比,土表覆砂增加了0~40 cm土层土壤体积质量及0~8 cm土层的土壤紧实度,而8 cm以下土层土壤紧实度小于荒地;西瓜产量和瓜周可溶性固形物量随微咸水补灌年限增加分别呈降低和先增加后降低的趋势。【结论】长期微咸水补灌提高了压砂地上层土壤体积质量和紧实度,同时也增加了土壤含水率和土壤盐分,西瓜产量随微咸水补灌年限增加呈下降趋势,而西瓜品质则有先提高后降低的趋势。

压砂地土壤质量演变特征及其退砂后土壤培肥建议

通过文献调研的方法,综合分析压砂地土壤物理、化学和生物学性质的演变特征。结果表明,压砂具有蓄水保墒作用,同时防止土壤水蚀、风蚀,减少水土流失。但随着压砂年限增加,压实作用造成土壤结构变差,土壤肥力和土壤关键酶活性呈降低趋势,土壤微生物结构发生变化,土壤连作障碍加剧,土壤质量总体呈下降趋势。从轮作休耕、节水高效栽培模式、深松深翻构建耕层、土壤快速培肥等方面,提出了退砂地土壤质量提升建议。

不同药剂苗期灌根对旱砂西瓜生长及产量和品质的影响

为筛选出防治旱砂西瓜连作障碍的适宜药剂,有效解决旱砂西瓜连作障碍问题。以靖远县主栽西瓜品种林丰金牌10号为指示品种,选用5种不同药剂在多年连茬旱砂西瓜田西瓜苗期进行灌根处理,分析比较了不同药剂处理对旱砂西瓜产量和品质的影响。结果表明,96%硫酸铜颗粒剂500倍液、2%中生·四霉素水剂1000倍液、根腾菌剂600倍液灌根处理的旱砂西瓜植株存活率最高,均为99%,较对照喷清水高1个百分点。1.8%辛菌胺醋酸盐水剂800倍液灌根处理旱砂西瓜叶片的叶绿素含量最高,为54.9 g/mg,较对照喷清水增加2.7 g/mg;根腾菌剂600倍液灌根处理旱砂西瓜叶片的氮素含量最高,为4.5 g/kg,与对照喷清水持平。1.8%辛菌胺醋酸盐水剂800倍液灌根处理防病效果最佳,对枯萎病的防效达到62.99%,对蔓枯病的防效达到68.32%。根腾菌剂600倍液灌根处理的旱砂西瓜折合产量最高,为62244.00 kg/hm^(2),较对照喷清水增产28.7%;1.8%辛菌胺醋酸盐水剂800倍液灌根、2%中生·四霉素水剂1000倍液次之,均为58187.25 kg/hm^(2),均较对照喷清水增产20.3%。96%硫酸铜颗粒剂500倍液灌根处理的旱砂西瓜果实中心糖、阳面边糖、阴面边糖含量均最高,分别为13.5%、11.0%、9.2%。综合比较,利用96%硫酸铜颗粒剂500倍液、根腾菌剂600倍液在旱砂西瓜苗期进行灌根处理,既能够显著防治砂田西瓜病害,又能够提高旱砂西瓜产量和品质,并且防治成本较低,效果较好,建议推广应用。

滴头流量对压砂土壤水盐分布及西瓜生长、产量的影响

【目的】探明微咸水灌溉条件下滴头流量对压砂地土壤水盐分布及西瓜生长和产量的影响。【方法】通过田间试验,设置Q1(2 L/h)、Q2(3 L/h)、Q3(4 L/h)3种滴头流量,研究滴头流量对灌水前后土壤水盐分布特征、西瓜生长、产量、果实品质及水分利用效率的影响。【结果】滴头流量越大,土壤水平湿润范围越大,膜间土壤含水率越高,滴头下方垂直湿润深度越浅。各处理0~100 cm土壤盐分经过一个全生育期均呈下降趋势,盐分减少量随滴头流量增大而增加。果实可溶性糖量随滴头流量增大呈先增大后减小趋势,Q2处理最大,分别较Q1、Q3处理提高了54.3%和22.3%;维生素C量随滴头流量增加呈先减少后增加趋势,Q3处理最高,较Q2处理提高了53.7%。西瓜产量与灌溉水利用效率均随滴头流量增大而增加,Q3处理产量分别较Q1、Q2处理提高了6.20%和3.56%,Q3处理的灌溉水利用效率分别较Q1、Q2处理提高了6.49%和3.72%。【结论】综合考虑土壤水盐再分布形式与西瓜产量、品质,适用于压砂地西瓜微咸水滴灌流量为Q3(4 L/h)。

不同微咸水灌溉方式对压砂地土壤水盐及pH空间变异的影响

掌握不同灌溉方式下压砂地土壤水盐及pH的空间分布规律可以有效提高微咸水的利用效率。利用田间取样、经典统计学、地统计学以及克里格插值法对比分析了滴灌和微喷灌0~40cm土层土壤含水率、电导率和pH值的空间变异特征。结果表明:微喷灌的土壤含水率略低于滴灌,0~40cm土层土壤含水率属于中等变异性,且具有中等强度的空间相关性。微喷灌0~20cm土层土壤平均电导率和离散化程度小于滴灌,同时,2种灌溉方式下0~20cm和20~40cm土层电导率的空间分布均表现出中等变异且具有较强的空间相关性;20~40cm土层的平均电导率小于0~20cm土层。无论微喷灌还是滴灌,调查地块的土壤电导率表现为中间位置低而地边较高,土壤含水率则在中间位置高而地边低。灌溉方式对土壤pH值的影响不显著,其空间变异性属于弱变异,但微喷灌条件下pH值具有较强的空间相关性。微咸水灌溉条件下压砂地抑制了表层土壤盐分累积,并存在向未覆砂的地块边缘聚积的现象。不同灌水方式下压砂地土壤水分和盐分均存在中等的空间变异性和空间自相关性,而pH值空间变异性较弱。研究结果可以为压砂地的微咸水合理利用提供理论依据。

基于地理探测器和GIS的压砂地砾石空间异质性及其影响因素分析

为探究压砂地不同粒径砾石空间异质性及其影响因素,基于压砂地102个采样点,对不同粒径砾石配比进行了描述性统计,通过半方差函数和全局空间自相关分析等地统计方法分析了压砂地不同粒径砾石的空间变异特征和聚集模式,并进一步利用地理探测器模型识别影响不同粒径砾石占比空间分异的主要影响因子,在此基础之上,选取主要影响因子协同地理加权回归克里格法对不同粒径砾石占比进行可视化,获取其分布特征。结果表明,不同粒径砾石的空间变异系数均大于10%,属中等变异。不同粒径砾石的空间异质比变化范围较大(0.26%~83.48%),其空间异质性受随机性因素和结构性因素共同影响。空间自相关分析显示各粒径砾石的全局Moran′s I均高于0.674,且Z值均大于1.96,表明不同粒径砾石具有极显著的空间依赖特征,呈聚集性分布。地理探测器模型识别表明压砂地不同粒径砾石的空间分异的解释力由大到小依次为种植年限>坡向>地表粗糙度>坡度>剖面曲率>平面曲率>地表起伏度,种植年限的单因子解释力明显高于其他因子。不同环境条件下压砂地土体中不同粒径砾石空间分布差异明显且呈聚集性分布特征。种植年限、坡向和地表粗糙度是压砂地不同粒径砾石空间分布状况的主要影响因子。

宁夏压砂地生态修复对策及建议

压砂地种植作为一种独特的砂田耕作种植方式,为宁夏当地农民创造了良好经济效益。但由于初期追求经济效益而盲目开荒,导致土壤沙化、植被退化、生态恶化的问题日益凸显。本文分析了宁夏压砂地种植过程中存在的问题,同时提出压砂地生态修复的对策及建议,旨在为推进生态环境修复及促进生态环境绿色可持续发展提供借鉴参考。

甘肃砂田西瓜覆膜补灌效应研究

为证明集雨补灌对砂田西瓜是否有效,在甘肃省皋兰县进行了集雨补灌效应研究,结果表明:在西瓜全生育期,各处理的土壤水分呈波动性下降,0～120cm土层含水量下降幅度在2.59%～4.13%之间,补灌量愈大,土壤含水量的下降幅度愈小。砂田西瓜全生育期耗水较少,不同补灌量处理的耗水量在175.9～218.9mm之间,比小麦等大田作物低100mm以上。灌水量对结瓜期的耗水量影响很大,灌水量增加,结瓜期耗水量增大。不同补灌量处理的西瓜产量差异达显著水平,随灌水量的增加,产量、单瓜重和采收瓜数相应增加。补灌量对西瓜的含糖量也有影响,补灌量低于45mm,各处理之间含糖量的差异不大,补灌量为67.5mm,西瓜含糖量降低4.4%以上。适量补灌可以提高西瓜水分利用效率,其中滴灌67.5mm处理水分利用率最高,达到267.2kg·hm-2·mm-1,比不补灌处理提高17.0%。但随灌水量的增加,灌水效率降低,单方水产值减少。由于补灌对西瓜的产量、含糖量和水分利用率都有影响,只有适时适量补灌,才能即提高产量和水分利用率,又不降低品质。研究结果证明,砂田集雨补灌栽培西瓜是集雨水利用的一种较经济高效的方式,但最佳补灌量应控制在45mm左右为宜。