Productivity of hedgerow shrubs and maize under alleycropping and block planting systems in semiarid Kenya

A field experiment was conducted for eight cropping seasons from 1988 to 1991 in semiarid Machakos, Kenya, to compare the productivity of shrubs and crops in intercropping (alleycropping) versus block (sole) planting systems. The study, conducted in a split-plot experiment with three replications, consisted of two tree species (Leucaena leucocephala andSenna siamea syn.Cassia siamea) in the main-plots and combinations of two planting systems (alleycropping and block planting of the shrubs and maize) with five different ratios of land allocation for the shrub and crop (1000, 1585, 2080, 2575, and 0100) in sub-plots. Thus, a sole maize and a sole tree were included in the subplot treatments. The spacing between hedgerows of shrubs in intercropping was 6.7, 5, and 4 m, respectively, corresponding to 15, 20, and 25% land allocation to shrubs. The trees were pruned to 0.5 m height four times a year. Intercropped hedgerows of senna and leucaena produced 10% and 24% more biomass than their respective block planting systems. On average, leucaena produced more biomass than senna. Maize alleycropped with leucaena yielded 16% less grain than sole-crop maize, whereas senna intercropping caused hardly any maize-yield reduction. Compared with the respective sole-crop systems, leucaena intercropping did not affect land equivalent ratio (LER), whereas LER increased by 28% with senna intercropping. The different tree:crop land occupancy ratios did not affect the production of either the component species or of the total system, except that LER declined with incrreased spacing between hedgerows. It is concluded that in semiarid highlands of Kenya, leucaena and crops should better be grown in sole blocks, not in alleycropping. In the case of slow-growing species such as senna, intercropping is worthwhile to consider only if the additional labour needed does not pose a serious problem for management, and the species has fodder value.     

Influence of root pruning and cutting interval ofLeucaena hedgerows on performance of alley croppedrabi sorghum

The influence of root pruning and cutting interval ofLeucaena hedgerows on alley croppedrabi sorghum was investigated. Paired (60 cm)Leucaena hedgerows spaced 6.6 m wide were subject to either root pruning, using a country plough during mid-kharif season, or no root pruning. The cutting frequency ofLeucaena hedgerows ranged from one month to six months during therabi cropping period. The effect on soil moisture, crop growth, yield and yield components ofrabi sorghum was examined.Root pruning ofLeucaena hedgerows increased grain and stover yields of the alley croppedrabi sorghum by 33 and 17%, respectively, over root not pruned hedgerows. Similarly, shorter cutting intervals (one and two months) increased crop yields as compared with longer cutting intervals (three and six months). The growth (height and dry matter) of the crop was similarly influenced. Soil moisture studies indicated that the competition between crop and hedgerows was considerably reduced by the root pruning. The results clearly showed that the competition between hedgerows and arable crop can be reduced considerably by root pruning and frequent cutting (at one to two months interval) of the hedgerows.     

Soil nitrogen dynamics in alley cropping and no-till systems on ultisols of the Georgia Piedmont, USA

On highly-weathered Ultisols of the Georgia (USA) Piedmont, a combination of no-till agriculture and alley cropping presents an option for rapidly increasing soil nitrogen availability while restoring long-term soil fertility. Three years after the establishment of Albizia julibrissin hedgerows and no-till agriculture trials, we measured inorganic soil nitrogen (NO₃ ^-–N and NH₄ ^-–N) and net nitrogen mineralization during a 4-month field study and a 14-day laboratory study . We also measured the influence of tree leaf amendments on grain sorghum production and N uptake. Soil nitrate increased four-fold within two weeks of adding Albizia leaf mulch. Soil ammonium did not increase as rapidly nor to the same extent after tree mulch addition. Averaged over the 4-month study, soil nitrate and ammonium were 2.8 and 1.4 times higher in the alley-cropped than in the treeless no-till plots. Net nitrification and mineralization were no higher in the alley cropping plots, during either field or laboratory incubations. Tree mulch additions enhanced crop biomass production and N uptake 2 to 3.5 times under both high and low soil moisture conditions. Our study demonstrates the dramatic short-term impacts of Albizia mulch addition on plant available nitrogen. Combined with no-till practices, alley cropping with Albizia hedges offers Piedmont farmers an option for reducing reliance upon chemical N fertilizer while improving soil organic matter levels. This revised version was published online in August 2006 with corrections to the Cover Date.     

Conservation farming practices for small reservoir watersheds: a case study from Sri Lanka

Traditional agricultural villages in the dry zone of Sri Lanka are minor watersheds where small earth bank reservoirs provide water for irrigation and domestic purposes. The farmers practise rainfed farming on a shifting basis called chena in the reservoir catchments, which are being degraded due to soil erosion. The consequent sedimentation in reservoirs has reduced the extent of irrigation, and the total farming system has lost its ecological balance and economic sustenance. The present study aimed at identifying suitable farming methods for reservoir catchments in order to prevent further deterioration.The investigation was carried out on plot basis to assess soil loss and runoff from forest, scrub and cultivated lands as well as from four other types of farming lands namely plough-farming, bund-farming and two conservation farming practices: strip mulch and graded hedgerow farming. In graded hedgerow farming hedgerow trees are planted across the slope with a mild gradient of 0.4–0.5%. The study was carried out in a reservoir watershed at Maha Illuppallama, Sri Lanka during 1989/90 major rainy season.Results indicated that the two conservation farming practices generate 33–34% annual runoff while replenishing soil moisture of the watershed. Soil loss data showed that the conservation farming practices provide more than 80% protection against soil erosion while bunding can provide only 40% protection compared to existing shifting cultivation practices.     

Post-process of Finite Element Method in Electrical Impedance Tomography

In the research of electrical impedance tomography (EIT), each calculation may produce a large amount of data(such as conductance , resistance etc.). The rule of these data is not clear and is hard to understand. How to express the calculation result by means of image in order that such parameters as conductance and resistance can be grasped from the image is significant in analyzing and understanding the calculation result and is helpful to the doctor. This paper has discussed the realization of the post-process of finite element method in electrical impedance tomography and we have developed the software of the post-process of finite element method using Visual C++ .NET and OpenGL. Some problems in drawing the contour line and color contour band have been solved properly.     

Models of Steep Cultivated Slop Land Returning Forest

Slop land resource is an important part of land resource in China and its utilization and conservation deeply affect the stability of environment. It will playan important role on soil land water conservation and improvement of mountain area eco-environment for cultivated slop land to be returned to forest for instance: agroforestry method, contour hedgerow technique, plant barrier, terraced field and so on up till now. The models of agroforestry and terraced field are use extensile, but comparing with other methods of slop land utilization, contour hedgerow technique cost is less and its effect in soil water conservation and soil fertility sustaining is terrific. So it is necessary to be applied and popularized.     

Scanning Beam Method for the Contour Graph

The tracing method is applied to generate the contour graph, it is difficult to find the start point of the interior closed contour beam. This paper presents a general scanning beam method which can be applied to generate color contour graph for elements with arbitrary shape by the object-oriented programming. We give visualization of the elements of triangle the element with 3 Points, triangle element with 6 Points, quadrilateral element with 4 Points, quadrilateral element with 8 Points, quadrilateral Element with 9 Points and the example by the MFC of Visual C++ R6.     

A 3D Thin Slot Model for Shielding Analysis

The apertures or slots on shielding enclosure are the main factor to influence the shielding performance.The simulation for thin slots in the electromagnetic shielding analysis has been a bottle-neck.Subcellular models of thin slots in the finite-difference time-domain(FDTD) method are investigated.A 3D thin-slot algorithm based on contour path(CP) method is presented for the application to shielding enclosure.The accuracy and the applicability to the slot width are validated with finer mesh model or capacitive thin-slot formalism(C-TSF) for slot models with different width.     

基于平滑轮廓对称轴法的苹果目标采摘点定位方法

果实采摘点的精确定位是采摘机器人必须解决的关键问题。鉴于苹果目标具有良好对称性的特点,利用转动惯量所具有的平移、旋转不变性及其在对称轴方向取得极值的特性,提出了一种基于轮廓对称轴法的苹果目标采摘点定位方法。为了解决分割后苹果目标边缘不够平滑而导致定位精度偏低的问题,提出了一种苹果目标轮廓平滑方法。为了验证算法的有效性,对随机选取的20幅无遮挡的单果苹果图像分别利用轮廓平滑和未进行轮廓平滑的算法进行试验,试验结果表明,未进行轮廓平滑算法的平均定位误差为20.678°,而轮廓平滑后算法平均定位误差为4.542°,比未进行轮廓平滑算法平均定位误差降低了78.035%,未进行轮廓平滑算法的平均运行时间为10.2ms,而轮廓平滑后算法的平均运行时间为7.5ms,比未进行轮廓平滑算法平均运行时间降低了25.839%,表明平滑轮廓算法可以提高定位精度和运算效率。利用平滑轮廓对称轴算法可以较好地找到苹果目标的对称轴并实现采摘点定位,表明将该方法应用于苹果目标的对称轴提取及采摘点定位是可行的。     

香根草植物篱护坡反季节施工技术

 在萍莲319国道改建工程中运用香根草(Vetiveriazizanioides)植物篱护坡反季节施工技术,在石块砾石区下边坡,香根草成活率达90%,在煤土堆积下边坡,香根草成活率达94%。表明香根草植物篱技术在江西萍乡10—11月反季节应用非常成功,证明了香根草等高植物篱技术防护公路边坡的有效性,也说明在极劣地利用香根草进行生态恢复,一年四季皆可取得成功。这为香根草等高植物篱技术的广泛运用和推广提供了新的施工方法。