Contour Cultivation Research Articles

The effects of minimal tillage and contour cultivation on surface runoff, soil loss and crop yield in the long‐term Woburn Erosion Reference Experiment on sandy soil at Woburn, England

Abstract. Over a 10‐year period, runoff and soil erosion on the plots of the Woburn Erosion Reference Experiment were concentrated in periods with sparse vegetation cover: in winter after the late planting of cereals; in spring after the planting of beets; or when soils were bare after harvest. The mean event runoff of 1.32 mm from plots cultivated up‐and‐downslope was significantly greater (P<0.05) than that from plots cultivated across‐slope (0.82 mm). However, mean event soil loss was not significantly different between the two cultivation directions. No significant differences were found between minimal and standard cultivations. Mean event runoff from the across‐slope/minimal tillage treatment combination (0.58 mm) was significantly less (P<0.01) than from the up‐and‐downslope/minimal tillage (1.41 mm), up‐and‐downslope/standard tillage (1.24 mm), and across‐slope/standard tillage (1.07 mm) treatment combinations. Runoff from the across‐slope/standard treatment combination was significantly (P<0.05) less than from the up‐and‐downslope/minimal tillage treatment. The across‐slope/minimal tillage treatment combination had a significantly smaller (P<0.05) event soil loss (67 kg ha−1) than the up‐and‐downslope/standard tillage (278 kg ha−1) and up‐and‐downslope/minimal tillage (245 kg ha−1) combinations. Crop yields were significantly (P<0.05) higher on across‐slope plots in 1988, 1996 and 1997 than on up‐and‐downslope plots, and were also higher (but not significantly) on the across‐slope plots in 7 of the 8 remaining years. Minimal cultivation decreased yield compared with standard cultivation in one year only. We recommend that across‐slope cultivation combined with minimal tillage be investigated at field scale to assess its suitability for incorporation into UK farming systems.

The effects of minimal tillage and contour cultivation on surface runoff, soil loss and crop yield in the long-term Woburn Erosion Reference Experiment on sandy soil at Woburn, England

The effects of minimal tillage and contour cultivation on surface runoff, soil loss and crop yield in the long-term Woburn Erosion Reference Experiment on sandy soil at Woburn, England

Effects of land use on soil erosion and nutrient loss in the Three Gorges Reservoir Area, China

Abstract. By comparing field measurements from 1989, 1997, and 1998, the differences between farmland (sloping farmland, sloping farmland with contour cultivation, terraced farmland) and orchard (terraced orchard, unterraced orchard), in the Three Gorges Reservoir Area, were significant for runoff (P<0.01), erosion (P<0.05) and nutrient loss (P<0.05). Taking into account economic costs and environmental influences, reasonable and sustainable land use on slopes of 25° in the Three Gorges Reservoir Area should be unterraced orchard.

Characteristics and Modeling of Runoff Hydrographs for Different Tillage Treatments

Surface runoff rate is a critical variable in determining the rate of soil erosion and sediment transport. Rainfall and runoff data at 1‐min intervals from an experiment site at Khon Kaen, Thailand, were used to test a three‐parameter runoff model originally developed for bare plots in relation to soil erosion studies. The site has a sandy soil with a slope of 3.6%. Plot length and width were 30 and 5 m, respectively. Four tillage treatments with three replicates each were considered: up‐ and down‐slope cultivation, two contour cultivation treatments with tillage depth of 25 and 50 cm, respectively, and no tillage. Runoff data for 200 individual runoff hydrographs showed that runoff amount and peak runoff rate for the no tillage treatment were significantly less than those for other treatments at the site. On average, runoff amount and peak runoff rate for the no tillage treatment were 37 and 44%, respectively, of those for the up‐ and down‐slope cultivation. Results for contour cultivation practices are between the two extremes, although the water retention was not greater with greater tillage depth as we originally thought would be the case at the site. For these 200 runoff events for the four treatments, the model for runoff hydrographs worked well, with an average coefficient of efficiency of 0.90 and an average standard error of 0.88 mm h−1 The model performance is particularly good for large storm events with high volumetric runoff coefficient. The three model parameters vary considerably from event to event and from treatment to treatment. The initial infiltration amount was found to be inversely related to prior 10‐d rainfall at the site; the spatially averaged maximum rate of infiltration can be related to the maximum retention or the Soil Conservation Service (SCS) Curve Number, and the hydrologic lag time is least variable among different storm events and tillage treatments, but tends to decrease with peak runoff rate.

Landscape benching from tillage erosion between grass hedges

Grass hedges are narrow (1–2 m wide) parallel strips of stiff, erect, grass planted near to or on the contour of fields but crossing swale areas at angles convenient for farming. They serve as guides for contour cultivation, retard and disperse surface runoff, cause deposition of eroded sediment, and reduce ephemeral gully development. After three years of tilled fallow between mixed-species hedges, the average grade of 18 m wide tilled strips between 1.5 m wide hedges was reduced from 0.068 to 0.052 as a result of surface lowering below hedges and on the shoulders of swale areas combined with increases in elevation above hedges. Annual surveys show progressive lowering of high spots and filling of low spots as contours lines more closely aligned with hedges. Survey data indicated annual erosion rates of nearly 250 t ha −1 year −1. Both RUSLE and WEPP over-predicted erosion rates, partly because backwater and slope modification affects were not considered. A tillage translocation model predicted enough soil movement to account for 30–60% of the observed changes. A combination of tillage translocation and water erosion/deposition provides the best explanation for the observed aggradation/degradation patterns.

Agroforestry for soil and water conservation in the western Himalayan Valley Region of India. 1. Runoff, soil and nutrient losses

Erosion losses were investigated in a field experiment, from 90 × 15 m erosion plots at 4% slope in the western Himalayan valley region of India. The plots were planted with Leucaena leucocephala and Eucalyptus hybrid, either as block plantation or in alley farming with maize (Zea mays), Chrysopogon fulvus grass or turmeric (Curcuma longa). The treatments also included contour planting of sole maize, sole Chrysopogon fulvus grass and a clean weeded cultivated fallow. During the nine year study period, the average annual monsoon rainfall was about 1000 mm and it caused 347 mm runoff and 39 Mg ha-1 soil loss per year from fallow plots. The runoff and soil loss were reduced by 27% and 45% by contour cultivation of maize. Contour tree-rows or leucaena hedges reduced the runoff and soil loss by 40% and 48%, respectively, over the maize plot, reducing soil loss to about 12.5 Mg ha-1. This reduction in erosion was primarily due to the barrier effect of tree or hedgerows and micro-terraces formed through sediment deposition along the contour barriers. Such vegetative measures, that are productive while being protective, offer viable alternative for erosion control in areas with gentile slopes of the valley region. High density block plantations of eucalyptus and leucaena almost completely controlled erosional losses and can be recommended for steeper slopes that are vulnerable to heavy erosion.

Soil and nutrient loss under rozelle ( Hibiscus subdariffa L. var. altissima) at Khon Kaen, Thailand

Rozelle ( Hibiscus subdariffa L. var. altissima) was grown in hydrologically defined plots at Khon Kaen, Thailand (latitude 16°30′N, longitude 102°50′E, altitude 195 m). The loss of water, soil and plant nutrients from these plots under different types of soil management was measured for the three growing seasons from 1989 to 1991. Plots were 30 m long, 5 m wide, and slope 3.6%, and the soil was a loamy sand with 5% clay and 79% sand. Treatments included up and downslope cultivation, contour cultivation with and without subsoiling, and no tillage. A bare plot was also installed to measure soil erodibility parameters. Runoff and soil loss from treatment plots was greatest from the up and downslope cultivation treatment, though not exceeding 20% of rainfall or 4 tonnes/ha respectively in any growing season. Despite the modest loss of soil by water erosion, the average enrichment ratio for nitrogen was 5.5. Thus the loss of nitrogen would be important on this sandy soil, especially as rozelle is commonly grown in this region with little or no fertilizer input. Soil, water and nutrient loss was also measured for a bare soil plot. Soil loss from this plot was about ten times higher than for the most erosive treatment. Most eroded sediment was transported from the bare plot in broad, shallow rills in which the sediment concentration was close to the transport limit, which was less than the concentration produced by rainfall detachment and re-detachment because of the low slope of the plots, and the high detachability of this soil. Of the four management treatments investigated, contour cultivation emerged as the most practicable. Subsoiling was ineffective in further reducing runoff and soil loss, and if no cultivation was carried out, plant yield was reduced, even though this treatment was most effective in reducing soil erosion.

Application of AGNPS to model nutrient generation rates under different farming management practices at the Gunnedah Research Centre catchment

Data collected at a conservation tillage trial site operational between 1971 and 1986 were used to assess the performance of the Agricultural Non-Point Source model (AGNPS). Eight trial plots, each of about 1 ha (average slope of 3.8%), were established on the black earths of paddock 2 at the Gunnedah Research Centre, New South Wales. The plots were subjected in pairs to stubble-burning, stubble incorporation, stubble-mulching, and no-tillage treatments. Runoff and peak flow rate from the plots, resulting from 5 rainfall events between 1982 and 1986, were used to calibrate the hydrology module of AGNPS. Hydrologic simulations for each plot and associated tillage treatment performed after calibration showed that conservation farming practices could effectively reduce runoff and peak flow rate. AGNPS was also used to simulate nutrient generation rates, defined as the transport of soluble and sediment-adsorbed nitrogen and phosphorus in runoff and sediment discharge, for the whole catchment for a number of rainfall events. The model predicted that nutrient movement could be reduced using best management practices, including the implementation of contour banks, contour cultivation, and no tillage. Additional information related to soil chemical properties and pore/surface water nutrient content could improve model performance.

Tillage methods related to soil and water conservation in south Asia

Research on different tillage systems and their role in soil and water conservation in south Asia is reviewed. Tillage has shown marked influence on soil hydraulic characteristics and to some extent on soil chemical and biological properties particularly organic matter cycling. The importance of conservation tillage in reducing runoff, soil loss and in ensuring sustainable agricultural production in the region is emphasized. The role of other tillage practices, for example contour cultivation, contour bunding, terraces and tied ridging, in increasing the profile water storage is discussed.

African soil erosion — nature undone and the limitations of technology

AbstractA wide range of mechanical soil conservation techniques commonly used in Africa are reviewed in a politico‐economic framework. Three factors within this framework play a significant role in the adoption of mechanical soil conservation techniques. These are: (a) land considerations, such as land availability and tenure, and farm size; (b) capital and labour constraints; and (c) access to, and functioning of, institutions.Hypotheses which are concerned with the relationships between these factors and the likelihood of farmers adopting soil conservation techniques are introduced. Case studies drawn from Kenya, Lesotho, Malawi, Swaziland and Sierra Leone, as well as from Jamaica, are used to test these hypotheses in relationship to such techniques as terracing, grass strip cultivation, bunding, and contour cultivation. Greater reliance on local knowledge and indigenous soil conservation techniques seems to provide the best solution to the introduction of mechanical soil conservation techniques.

The Problems of the Utilization of Slope Lands in Japan

In Japan, where a dense population is crowded together on a few small plains, it is not surprising that the use of sloping land in the mountains, which comprise 67% of Japan's area, has been promoted in various ways. In some regions the cultivation of steep land is amazingly intense. In this essay, only upland fields of considerable slope are discussed. The categories treated are 1) the steep field as a special type of upland field, 2) the regional distribution of steep upland fields, and 3) the problems of their future development.1. Upland fields in general are subordinate in importance to paddy fields, but in some regions they are of first. importance. Broadly speaking, there are two sorts of upland fields, those on flat elevated land, and those on steep slopes. A survey was made in 1942 to classify upland fields by degree of slope, as follows : those with 5° of slope, those whith 5°-15°, and those with more than 15° of slope. Those in the latter category comprised about 50, 000 hectares, or nearly one-fifth of the total area of all upland fields. In fact, the greater part of these had a declivity of 20°-30°, and some reached 35° of slope. The soils of these fields, which comprise 2% of the mountain lands of Japan, are infertile lithosols.Figures 1 to 4 show the distribution of steep upland fields : Figure 1 ……the ratio of steep fields to all upland fields, by prefecture ;Figure 2 ……the ratio of upland fields to all cultivated fields ;Figure 3 ……the ratio of steep fields to all upland fields, by gun (district);Figure 4. ……the relative density of steep fielde to total area.The most important steep upland field regions are the mountainous regions in the Outer Zone of Southwest Japan, namely Shikoku and the Kii Peninsula ; the Inland Sea Region in the Inner Zone ; and peninsular regions of Kyushu. The mountainous regions of Central Japan are secondary to the above areas in importance.2. The development of steep upland fields has been mainly related to self-sufficient food crops both on intensively cultivated permanent fields and on the much less important extensively cultivated shifting fields. Two morphological types of land use are distinguished : a) use of the natural slope with no modification, a type prevalent in Central Japan, and d) modification by terracing, a type dominant in Southwest Japan.In the use of natural slopes, contour cultivation is strictly adhered to, and much organic material is added to maintain the soil fertility. The yield of crops such as barley, wheat and soy beans is higher on these fields than on terraced fields. Mulberry trees are grown in large areas, and in some localities the Konnyaku tuber (Amorphophallus konjac) is grown intercropped with barley. On terraced slope lands, bench terraces are constructed on the steeper slopes, an sloping terraces on the less steep slopes. Typical examples of these are seen in southwest Shikoku. The strong intensity of precipitation is one of the most important factors that make steep land cultivable only by making terraces. The main crops are barley and wheat in winter, and sweet potatoes in summer. These terraces are subject to soil erosion on the one hand, and to drought on the other, , resulting in meager yields of all crops except sweet potatoes.3. To improve the utilization of steep lands by agriculturists, it is necessary to plant profitable cash crops, such as sweet oranges, konnyaku tubers, and mulberry trees. The fundamental weakness, of steep upland field cultivation lies in the extensive cultivation of self-sufficient food crops, which require much labor per unit of area, and yield relatively little in return.

Water Supply and Food in India

IN a pamphlet entitled “Food and Irrigation Problems affecting India in General and Bombay in Particular”, Rao Bahadur N. S. Joshi discusses ways of meeting the estimated requirements of 1971. He is concerned mainly with the engineering aspects of the irrigation presumed to be needed; and though the nutritional discussion is mainly in terms of crop area and tonnages, the need for improved diet is not neglected. On account of the great distances, a general transfer of food from 'surplus' to 'deficit' provinces is impracticable. The solution is, in the author's view, a great increase in irrigation ; but in Bombay it is not possible to extend greatly the kind of barrage-and-eanal irrigation that has been a spectacular success in the river-plains regions. The pamphlet may be regarded as a reasoned critique of canal irrigation. Contour cultivation (bunding) may increase yields in hilly areas, but the crops suitable for upland cultivation are grains of low nutritional value, of which Bombay normally has a surplus ; and contouring is incompatible with storage from catchments. The ultimate solution for Bombay Province, therefore, is a very great increase in the number of small wells. The author suggests how these might be planned and financed, and in addition he shows how barrage and water-storage schemes could be provided so as to make the greatest possible use of all water resources. The pamphlet is stimulating, and has much value as a source of information regarding the current status and economics of irrigation and food-production in various provinces of India. The reader is left with the feeling that the main difficulty is social rather than engineering.