降雨强度对农业耕作措施水土保持作用的影响

利用人工模拟降雨试验,研究不同降雨强度下,不同农业耕作措施坡地水土流失特征。试验设计的坡地坡度分别为5°和15°,降雨强度分别为60、90、120 mm·h^-1;耕作措施分别为等高耕作、人工掏挖和人工锄耕,以相同坡度的平整坡地作为对照。结果表明：（1）随着降雨强度的增大,各耕作措施坡地产流量显著增大1.51倍以上,最大增加幅度为等高耕作坡地的2.28倍。而坡地产沙量在降雨强度较小时增加不显著,当降雨强度增大到120 mm·h^-1时,坡地产沙量显著增大;（2）与平整坡地相比,等高耕作在3个降雨强度下都具有明显的减流效益,减流量均大于15%,而人工锄耕和人工掏挖却不明显;（3）在5°坡地上,等高耕作和人工掏挖在3个降雨强度的减沙效益均大于25%,而人工锄耕减沙效益不明显;在坡度为15°、降雨强度为60 mm·h^-1和90 mm·h^-1时,人工锄耕和人工掏挖减沙效益与降雨强度关系无明显规律,在降雨强度为120 mm·h^-1时,3个耕作措施都不能有效降低坡地产沙量。可见,水土保持农业耕作措施具有降低坡地产流量的作用,而对于坡地产沙的作用存在明显差异,在大坡度和大降雨强度下,不仅不能降低坡地产沙,反而加剧坡地土壤流失。     

基于M-DEM黄土人工锄耕坡面微地形特征研究

黄土人工锄耕坡面微地形是地表径流和土壤侵蚀过程的重要影响因素。文中在1.0 mm/min雨强的人工模拟降雨试验条件下,采用微地形激光扫描测量方法获取5°人工锄耕坡面微地形相对高程,并进行拟合模型参数验证,进而构建了能反映真实地表情况的高精度M-DEM,并在ArcGIS中对其特征参量进行量化研究。结果表明:黄土人工锄耕坡面微地形起伏较小,整体属于凸形斜坡;虽在某些区域容易形成地表径流,但径流变化比较平缓,不容易形成较大的水流;微地形水系分维能较好地反映复杂微地形特征。论文可为在微地形层面进一步揭示黄土耕作坡面土壤侵蚀机理研究提供数据支持和方法参考。     

不同土地利用方式对丘陵山区坡面侵蚀产沙量的影响

选取安徽省霍山县大官山的典型研究区域,通过径流试验,分析了近20年6种典型土地利用方式的侵蚀产沙特性及影响因素.结果表明:不同土地利用方式对坡面侵蚀产沙量的影响依次是顺坡耕作区＞标准小区＞经济林区＞牧草区＞乔木用材林区＞梯田小区.在不同土地利用方式下,防止土壤流失最有效的是梯田,而顺坡耕作区水土流失量最大.坡面侵蚀产沙量与降雨侵蚀力表现为幂函数关系,且相关性达到了极显著水平.     

不同保护性耕作下冬小麦田杂草滋生情况调查研究

采用随机调查的方法,对不同保护性耕作处理下冬小麦田间杂草的种类和数量进行调查研究,发现不同的耕作处理对杂草种类和数量的消长有很大的影响.传统耕作、免耕、秸秆深松覆盖、高留茬深松覆盖四种处理,以免耕条件下杂草的种类和数量最多,秸秆深松覆盖、高留茬深松覆盖是控制冬小麦田间杂革滋生的一种有效措施.不同保护性耕作处理使冬小麦田间杂草种类与各杂草相对丰度均发生变化,各处理间Shannon多样性指教(H')和Mamclef物种丰富度指数(D)均存在差异,其原因可能是由于不同保护性耕作处理造成各处理间生态环境、土壤养分和土壤水分的不同,各种杂草的生长因而受其不同影响所致.     

耕作措施对玉米田耕层土壤微生物群落功能多样性的影响

为研究秸秆还田基础上不同耕作措施对土壤微生物群落功能多样性的影响,本文以渭北旱塬玉米田为研究对象,采用Biolog-ECO方法研究了6种耕作措施,即连年翻耕（C/C）、连年免耕（N/N）、连年深松（S/S）、免耕/深松隔年轮耕（N/S）、翻耕/免耕隔年轮耕（C/N）和深松/翻耕隔年轮耕（S/C）对土壤微生物碳源代谢能力的影响。结果表明,不同耕作措施下碳源代谢活性（AWCD）随培养时间的延长均逐渐增加,免耕、少耕的各耕作处理下碳源代谢活性较C/C处理显著提高了12.70%~54.54%,其中N/S和N/N处理的微生物多样性指数（丰富度指数、Shannon-Wiener指数和Simpson指数）显著高于C/C处理。主成分分析对第1和第2主成分起分异作用的主要碳源是氨基酸类、糖类和羧酸类物质,且是该地区土壤微生物利用的主要碳源。冗余分析表明有机碳（SOC）是影响微生物碳源代谢特征的主要因素。研究表明,从微生物群落碳源代谢角度考虑, N/S处理下的土壤微生物活性和功能多样性较高,是适宜该地区的耕作措施。     

京津水源区坡耕地土壤侵蚀特征分析

坡耕地是保障粮食安全与经济发展的重要资源.本文利用承德市南山径流场资料对不同坡长下径流深、含沙量及侵蚀量进行对比分析,结果显示:坡长和降雨强度都对土壤侵蚀有影响,随着坡长变化,导致土壤侵蚀量变化的两个主导因素不断变换.雨强小于0.25 mm/min时,坡面土壤侵蚀模数随坡长的增加而增大;雨强大于0.25mm/min时,随坡长的增加先增大后减小,最大侵蚀量总是出现在22 m坡长范围内.径流深均值与侵蚀量增量随坡长变化趋势一致,含沙量均值变化与雨强关系密切.所以治理京津水源区坡耕地水土流失,应在22 m坡长以内采取等高植物篱等措施,既可降低工程投入,又减少坡面土壤流失,提高土地生产力.     

不同耕作方式对小杂粮产量及水分利用效率的影响

采用深松耕、免耕、传统耕3种耕作方式,研究了陕北小杂粮产区不同耕作方式对小豆、糜子产量和水分利用效率的影响。结果表明,免耕和深松耕有利于改善土壤物理结构,增加土壤的蓄水保墒能力,提高水分利用效率,节水、节本、增产增效明显,是比较理想的耕作方式。     

黄土坡面不同土地利用与覆盖方式的产流产沙效应

研究不同地类坡地产流产沙规律,对定量评价林草措施的水土保持效益具有重要的意义。利用布设在山西省吉县蔡家川流域的10个径流小区资料,分析了不同土地利用/覆盖方式对产流产沙的影响,研究结果表明:草地拦蓄暴雨功能明显小于灌木与乔木林地;农地(坡耕地)是坡面侵蚀的主要土地利用类型,天然灌木林与混交林的防蚀功能明显大于人工纯林;水土保持林地拦蓄径流明显大于经济林。     

犁体耕作阻力模型仿真分析与试验研究

为进一步提高犁体耕作性能,分析影响犁体耕作阻力的因素,基于摩尔-库仑土壤剪切理论,建立了包含犁体结构参数、土壤物理特性和犁体工作参数的耕作阻力模型,耕作阻力表达式包含了犁铲尖和犁铧切削土壤阻力、土壤在犁壁上产生的摩擦力和翻垡过程土壤动量变化产生的阻力、犁壁翻垡使土壤势能增加产生的阻力、作用在犁铧和犁壁上的横向力产生的摩擦力、土壤横向运动对犁壁产生的阻力。基于新疆玉米地土壤物理特性,建立了两种高速犁体A和B的耕作阻力方程,在不同耕宽（0.35、0.42 m）、耕深（0.255、0.305 m）和耕速(2.22、2.5、2.78 m·s^-1)作业条件下对耕作阻力进行了理论、仿真和试验研究,分析了犁体耕作阻力的影响因素,结果表明,仿真值与计算值的平均误差为3.37%,试验值与计算值的平均误差为7.18%,试验值与仿真值的平均误差为3.71%。犁体耕作阻力与铧刃角呈非线性增长关系;与耕深呈三次函数增长关系;与耕速呈二次函数增长关系;犁体耕作过程的功率消耗与耕速呈三次函数的增长关系。提出设置合理的安全系数（s_f）,使拖拉机配套功率P_s     

坡耕地玉米苜蓿间作水分分布与运移

采用探头式中子水分测定仪与时域反射仪法相结合,对不同坡度坡耕地苜蓿玉米间作下土壤水分进行监测,结果表明:在5°、10°和15°三个坡度下,表现出随着坡度的增大,产流量也随之增大,且同一坡度间相比较,表现出坡面产流量顺序为单作苜蓿＜玉米苜蓿间作＜玉米＜裸地,较单作和裸地而言,间作可有效减少坡面径流;苜蓿耗水量大干玉米耗水...     

Effects of structural and depositional crusts on soil erosion on the Loess Plateau of China

Conventional tillage practices used on the Loess Plateau lead to different soil surface micro-topography which results in forming two types of soil crusts. The objective of this study was to explore the formation position, properties and erosion characteristics of structural crusts and depositional crusts under the influences of the microtopography in the rainfall experiments. Two simulated rainstorms were applied in the experiments. The first rainfall event was used for soil crust formation, then the following simulated rainfall storms at 40 mm h^?1, 60 mm h^?1, and 80 mm h^?1 rates were applied to the soil boxes set to a 17.6% (10°) slope under three tillage types (contour tillage, artificial digging, and straight slope conditions) to investigate the resulting runoff discharge rate and sediment yield on crusted soil surface. Results show that: (1) structural crusts formed on the mounds, and depositional crusts formed in the depressions after the first rainfall events; structural crusts exhibit a lower thickness, bulk density, higher porosity and shear strength than depositional crusts; (2) structural crusts increased the runoff yield less and decreased the sediment yield more than depositional crusts; and (3) the runoff yield was significantly greater, and the sediment yield was lower on the crusted soil surface than that on the uncrusted soil surface, regardless of the effect of the tillage treatments.     

Soil surface roughness change and its effect on runoff and erosion on the Loess Plateau of China

As an important parameter in the soil erosion model, soil surface roughness（SSR） is used to quantitatively describe the micro-relief on agricultural land. SSR has been extensively studied both experimentally and theoretically; however, no studies have focused on understanding SSR on the Loess Plateau of China. This study investigated changes in SSR for three different tillage practices on the Loess Plateau of China and the effects of SSR on runoff and erosion yield during simulated rainfall. The tillage practices used were zero tillage（ZT）, shallow hoeing（SH） and contour ploughing（CP）. Two rainfall intensities were applied, and three stages of water erosion processes（splash erosion（I）, sheet erosion（II） and rill erosion（III）） were analyzed for each rainfall intensity. The chain method was used to measure changes in SSR both initially and after each stage of rainfall. A splash board was used to measure the splash erosion at stage I. Runoff and sediment data were collected continuously at 2-min intervals during rainfall erosion stages II and III. We found that SSR of the tilled surfaces ranged from 1.0% to 21.9% under the three tillage practices, and the order of the initial SSR for the three treatments was ZT〈SH〈CP. For the ZT treatment, SSR increased slightly from stage I to III, whereas for the SH and CP treatments, SSR decreased by 44.5% and 61.5% after the three water erosion stages, respectively, and the greatest reduction in SSR occurred in stage I. Regression analysis showed that the changes in SSR with increasing cumulative rainfall could be described by a power function（R2〉0.49） for the ZT, SH and CP treatments. The runoff initiation time was longer in the SH and CP treatments than in the ZT treatment. There were no significant differences in the total runoff yields among the ZT, SH and CP treatments. Sediment loss was significantly smaller（P〈0.05） in the SH and CP treatments than in the ZT treatment.     

Reduction in field emergence and seedbank density of Galinsoga quadriradiata and other weeds after contrasting false seedbed strategies in organic vegetable fields

Mechanical weed control in low competitive, organic vegetable production systems is challenging, particularly in fields with large populations of Galinsoga spp. (Asteraceae). Various false seedbed techniques are used prior to crop planting or sowing to prevent weed emergence, albeit with variable success. This study investigated the impact of machinery type (flamer, hoe and harrow), number of passes (2 and 4), tillage depth (1–4 cm) and intensity (double and single hoeing, and hoeing with or without additional harrowing) on weed emergence and seedbank density in 0–5 cm topsoil of organic vegetable fields. False seedbed machinery that did not or minimally disturb the soil was most appropriate for preventive control of Galinsoga quadriradiata (Hairy galinsoga) and total weed seeds, with reductions in seedling emergence up to 99% and 73%, respectively, for flaming, and 74% and 67%, respectively, for 1 cm deep hoeing, 1 month after false seedbed creation. Compared with 1 cm deep hoeing, 1 cm deep harrowing was 16% less effective in the control of emerged seedlings, while flaming was highly effective in preventing weed seedling emergence, even after a low number of passes. Tillage intensity was less important than tillage depth for the reduction in weed emergence and seedbank density. Overall, tillage was more effective for seedbank reduction than flaming.     

Effect of soil management on soil erosion on sloping farmland during crop growth stages under a large-scale rainfall simulation experiment

Soil erosion on farmland is a critical environmental issue and the main source of sediment in the Yellow River, China. Thus, great efforts have been made to reduce runoff and soil loss by restoring vegetation on abandoned farmland. However, few studies have investigated runoff and soil loss from sloping farmland during crop growth season. The objective of this study was to investigate the effects of soil management on runoff and soil loss on sloping farmland during crop growth season. We tested different soybean growth stages (i.e., seedling stage (R1), initial blossoming stage (R2), full flowering stage (R3), pod bearing stage (R4), and initial filling stage (R5)) and soil management practice (one plot applied hoeing tillage (HT) before each rainfall event, whereas the other received no treatment (NH)) by applying simulated rainfall at an intensity of 80 mm/h. Results showed that runoff and soil loss both decreased and infiltration amount increased in successive soybean growth stages under both treatments. Compared with NH plot, there was less runoff and higher infiltration amount from HT plot. However, soil loss from HT plot was larger than that from NH plot in R1-R3, but lower in R4 and R5. In the early growth stages, hoeing tillage was effective for reducing runoff and enhancing rainfall infiltration. By contrast, hoeing tillage enhanced soil and water conservation during the late growth stages. The total soil loss from HT plot (509.0 g/m²) was 11.1% higher than that from NH plot (457.9 g/m²) in R1-R5. However, the infiltration amount from HT plot (313.9 mm) was 18.4% higher than that from NH plot (265.0 mm) and the total runoff volume from HT plot was 49.7% less than that from NH plot. These results indicated that crop vegetation can also act as a type of vegetation cover and play an important role on sloping farmland. Thus, adopting rational soil management in crop planting on sloping farmland can effectively reduce runoff and soil loss, as well as maximize rainwater infiltration during crop growth period.     

Best timing for glyphosate treatments and possible combinations with pre and post-emergence weed control practices in no-till maize

Use of reduced and no-tillage systems has increased in recent years due to concerns for ecological and economic sustainability of agricultural production. Effective weed control is a serious concern in reduced tillage production. This study was conducted to investigate weed control practices in reduced and no-till maize production. The most effective timing of glyphosate application, either before or after sowing, was investigated in combination with pre-emergence application of acetochlor (840 g a.i/L), post-emergence application of foramsulfuron (22.5 g a.i/L), and two hoeing treatments. The treatments were maintained on the same plots during 2011 and 2012 to evaluate the cumulative effects of the treatments. Main plot treatments consisted of four timings of glyphosate application: 20 or 10 days before sowing, day of sowing, 5 days after sowing, and an untreated control. Sub-plot treatments were: pre- plus post-emergence herbicides, pre-emergence herbicide plus rotary hoeing, post-emergence herbicide plus rotary hoeing, and post-emergence herbicide plus two hoeing treatments (rotary and lister hoe). In the main plots, the lowest weed biomass was produced in glyphosate treatments at sowing and 5 days after sowing; the highest biomass was produced in control plots and in the plots with glyphosate treatments 20 days before sowing. In the sub-plots, the greatest weed biomass was produced in plots with two hoeing treatments (rotary and lister hoe). Glyphosate treatments at sowing and post-emergence herbicide treatment combinations produced the best weed control. Economic analysis revealed that pre-sowing, non-selective herbicide treatments provided a slight increase in net profit. Mechanical hoeing decreased net income due to increased production costs. The highest income was obtained from the pre-emergence plus post-emergence herbicide treatment combinations with no glyphosate.     

Effects of inter-row hoeing and fertilizer placement on weed growth and yield of winter wheat

Inter‐row hoeing is known to control tap‐rooted and erect weed species more effectively in winter wheat than weed harrowing. However, little is known about its effectiveness for use in the spring in winter wheat grown at wide row spacing (240 mm) under the influence of different placement of fertilizer. Two field experiments, one in 1999 and one in 2000, were conducted to study the influence of fertilizer placement, timing of inter‐row hoeing, and driving speed on the weeding effect on different weed species and crop growth. Placement of fertilizer below the soil surface improved crop growth and grain yield in both years compared with placement on the surface, but the more vigorous crop did not give any better suppression of the weeds surviving hoeing. Timing was not important in one experiment, whereas hoeing twice beginning in early April was more effective in the other experiment where weed growth over the winter had been vigorous. Driving speed had no influence on either the weeding effect or the yield, except for one case where increasing speed reduced the control of well‐developed weeds. Compared with unweeded reference treatments, inter‐row hoeing reduced total weed biomass by 60–70% and tap‐rooted and erect weed species in particular by 50–90%. Sowing at 240 mm row spacing yielded less than 120 mm (Danish standard), and inter‐row hoeing for winter wheat needs to be adapted to narrower row spacing to avoid such yield decreases.     

Tillage and herbicide treatments with inter‐row cultivation influence weed densities and yield of three industrial crops

Field experiments were conducted in northern Greece in 2003 and 2004 to evaluate effects of tillage regimes (moldboard plowing, chisel plowing, and rotary tilling), cropping sequences (continuous cotton, cotton‐sugar beet rotation, and continuous tobacco) and herbicide treatments with inter‐row hand hoeing on weed population densities. Total weed densities were not affected by tillage treatment except that of barnyardgrass (Echinochloa crus‐galli), which increased only in moldboard plowing treated plots during 2003. Redroot pigweed (Amaranthus retroflexus) and black nightshade (Solanum nigrum) densities were reduced in continuous cotton, while purple nutsedge (Cyperus rotundus), E. crus‐galli, S. nigrum, and johnsongrass (Sorghum halepense) densities were reduced in tobacco. A. retroflexus and S. nigrum were effectively controlled by all herbicide treatments with inter‐row hand hoeing, whereas E. crus‐galli was effectively reduced by herbicides applied to cotton and tobacco. S. halepense density reduction was a result of herbicide applied to tobacco with inter‐row hand hoeing. Yield of all crops was higher under moldboard plowing and herbicide treatments. Pre‐sowing and pre‐emergence herbicide treatments in cotton and pre‐transplant in tobacco integrated with inter‐row cultivation resulted in efficient control of annual weed species and good crop yields. These observations are of practical relevance to crop selection by farmers in order to maintain weed populations at economically acceptable densities through the integration of various planting dates, sustainable herbicide use and inter‐row cultivation; tools of great importance in integrated weed management systems.     

几种工程措施对黄土区陡峭边坡植被盖度的影响及其机理

陡削以兰州新区的一段陡峭边坡作为试验地点,通过分析在植被重建初期经人工整地后形成的4种微地形(大圆形坑、小圆形坑、条形坑和原状坡面)的植被盖度特征及环境因子(土壤硬度和水分、地表和空气温度、坡位、无纺布)对植被盖度的影响,探寻能有效提高植被盖度的几种工程改造措施。研究表明:①铺设了无纺布坡面的植被盖度显著大于对照坡面;陡峭边坡不同坡位的植被盖度:下坡位>中坡位>上坡位(P<0.05),这与自然坡面植被盖度分布规律一致。②3种微地形的植被盖度均显著大于陡峭坡面,其中条形坑的土壤水分和植被盖度最大,最大盖度维持的时间最长。③微地形和坡面的植被盖度均与土壤水分呈显著正相关,与空气温度、地表温度均呈显著负相关;微地形的土壤硬度(3kg·cm^-2)适宜植物生长,大于该值会对植被生长产生抑制作用;铺设无纺布有利于促进上坡位的植被生长,使坡面植被分布更均匀。研究结果表明,在陡峭边坡坡度、坡位和温度等无法改变的情况下,选择对压实的坡面进行整地翻耕处理,增加长条坑的数量并铺设无纺布等有效的工程改造措施,能显著增加植被盖度,促进植被恢复。