Soil Moisture Conservation Methods, Techniques, Tips
The important objective of soil moisture conservation is to minimize the amount of water lost from the soils through evaporation (water loss directly from the soil) and transpiration (water loss occurring during the plants) or combined, the evapotranspiration. Preserving soil moisture is an important means to maintain the required water for agricultural production, and helps minimize irrigation needs of the crops. This is mainly important in areas where rainwater and groundwater resources for irrigation are scarce or decreasing due to climate change or other causes.
There are a variety of methods that can be used for soil moisture conservation. Most of these are moderately low cost and complexity approaches, mainly relying on the presence of required materials and technical capacity locally. Many of the methods rely on providing several kinds of cover for the soil to minimize evapotranspiration and direct soil exposure to heat and sun. Normally, most methods used for soil quality improvement and conservation will yield benefits to soil moisture conservation.
Effect of different soil preparations on moisture conservation:
In the year 1986-87, an experiment was conducted to monitor the effect of different soil moisture preparations are pitting, trenching, saucer shape pits and ploughing on the growth of seedlings of different species.
The normal practice of trenching all along the contour lines across the slopes is an old technique of soil and water conservation in dry areas. However, systematic experiments have not been carried out to assess the various types of soil conservation measures. In the year 1987-88, construction of check dams and gully plugs was undertaken along with the planting of different species in Nandi hills as a measure to conserve soil and moisture.
The accumulation of silt by check dams is considerable, indicating that soil erosion is getting arrested. Moreover, planting of Agave and Bamboo has helped in stabilizing the gullies. There was an attempt to plant Khus grass to check soil erosion. It has proved successful in some of the eroded areas.
Different methods of soil moisture conservation:
Examples of methods for reducing excess soil moisture loss are given below;
Mulch is a layer of organic or inorganic material that is placed in the root zone of the plants. Examples of mulch materials contain straw, wood chips, peat. Inorganic mulch in the form of plastic sheeting is also used. Mulching is most fitting for low to medium rainfall areas, and less suited for areas with very wet conditions.
For arable soils, the most efficient conservation practices for reducing surface evaporation are those that provide some degree of surface cover for the soil. A surface cover can be best provided by mulches or by tillage practices that leave plant residues on the soil surface. Mulch is any material placed on a soil surface for the function of reducing evaporation or controlling weeds. Mulches act as barriers to the movement of moisture out of the soil. They can be either natural that is straw, wood chips, peat or man-made that is transparent or opaque plastic sheeting. Mulches can enhance soil temperature, depending on the type of mulch being used.
In addition to reducing evaporation, vegetative mulches can decrease the spread of soil-borne diseases, reduce weed growth, reduce soil erosion, and provide nutrients and organic matter and aid in infiltration. Mulches develop infiltration by protecting the soil surface from the impact of raindrops and eliminating soil crusting. Mulches can, however, be expensive and labor intensive to get, transport and apply to the soil. Mulching is generally more practical for high-value crops such as vegetables and berries.
Specially prepared plastics can control evaporative loss. Black plastic can effectively control weeds. These types of mulches are often useful by machinery and there are holes or slits present for plants to grow through. These mulches are generally used for vegetable and small fruit crops.
Cover crops are grown as a conservation measure either through off-season or for ground protection under trees. These add organic matter to the soil. All these give good cover from the erosion control point of view and at the same time furnish hay or fodder and provide as soil-building crops. These grow under trees to keep the soil from the impact of water drops falling from the canopy mostly important for tall trees like rubber where the height of fall is more.
Contouring process is to apply all tillage practices, such as, ploughing, planting, cultivation & harvesting on the contour that is, across the slope rather than up and downhill. In regions of low rainfall, this helps in soil conservation of moisture and in humid areas reduces erosion by reducing surface runoff. The furrows between the ridges developed by contour tillage practices catch and hold the water, thereby, checking the high water velocity, which erodes soil and causes sheet, rill or gully erosion. On steep slopes or below conditions of high rainfall intensity and soil erodibility, contour farming alone will increase gullying because row breaks can release stored water. Under such conditions, they are complemented by strip cropping.
Green manure is plant material which is grown for the sole function of eventually being incorporated into the soil while still lush and fresh. Green manuring function is to add organic matter to the soil, returns nutrients to the soil and improves soil structure.
In order to be used as green manure, a plant must have the following characteristics:
(i) Rapid growth,
(ii) Grow well under local conditions and
(iii) Make a large succulent canopy. Green manures are often legumes or plant grasses. Some examples are sweet clover, alfalfa, and ryegrass. Legumes give the additional benefit of nitrogen fixation, the conversion of atmospheric nitrogen into plant available forms.
Reducing or, in extreme cases, completely eliminating the tillage to keep healthy soil organic levels, which increase the soils capacity to absorb and retain water. Conservation tillage is a specific kind of such approach where crop residue is left on the soil to reduce evapotranspiration, and care for soil surface from wind, sun and heavy rain impacts.
Conservation tillage is any technique of soil cultivation that leaves previous crop residue on the field before and after planting the next crop. It decreases soil erosion, runoff, water pollution, CO2 emission, and fossil fuel. Conservation tillage methods contain no-till, strip-till, ridge-till and mulch-till. The no-till method involves planting crops directly into a residue that has been not at all, while in strip-till narrow strips are tilled and the rest of the field left untilled (strip-till). In Ridge-till row crops are planted directly on permanent ridges of 10 to 15 cm by clearing previous year’s crop residues to form ridge tops only. Mulch-till is any reduced tillage system that leaves at least one-third of the soil surface covered with crop residue.
Crop rotation is growing a series of different kinds of crops in the same area in sequenced seasons. It is done so that the soil of farms is not used for one set of nutrients. It helps in reducing soil erosion, increases soil fertility and crop yield. Examples of crop rotation contain rotating deep-rooted and shallow-rooted crops that make use of previously unused soil moisture, as plants describe water from different depth levels within the soil. Crop rotation may improve soil fertility and help control pests and diseases.
In this mixed cropping system, two or more than two crops are raised in the same land and at the same time. The mixed cropping is also called as intercropping or co-cultivation. The advantages of mixed cropping contain better utilization of soil nutrients, low weeds and insect pests, resistant to climate extremes, increase in overall productivity and the use of limited resources to the fullest extent.
Mechanical practices are engineering measures used to manage soil erosion from sloping land surface. The purpose of constructing the mechanical methods is to (1) to increase the time of stay of runoff water to raise the infiltration time in the water, (2) to break the land slope, hence reducing the velocity of the runoff water. Bunds and terraces are mechanical methods used to control soil erosion.
Read: Vanilla Cultivation.
A terrace is an earth embankment, constructed across the slope to manage runoff and thus reduces the soil erosion. Terraces are performing as a slope divider. The terraces can be divided into two groups. Bench terrace reduces land slope, whereas broad support terrace removes or retains water on sloping land. The original bench terrace organism consists of a series of flat shelf-like areas that convert a steep slope of 20 – 30 percent to a series of level, or nearly level benches. The broad base terrace is a broad surface channel or embankment make across the slope of rolling land. On the source of primary function, the broad base terrace is further classified as Graded or Channel Type and Level or Ridge Type. The primary purpose of the graded terrace is to remove excess water in such a way as to minimize erosion. Erosion is controlled by reducing the slope length and conducting the intercepted runoff to a protected outlet at a non-erosive velocity. The primary purpose of the level terrace is moisture conservation. In low to moderate rainfall area, they trap and hold rainfall for infiltration into the soil profile. They can be used in high rainfall areas if the soil is permeable.
Based on the functional requirements, they can be classified into two types: Contour bunds storage of water and Graded bunds safe disposal of excess water.
Bunds are related to the terraces which have a narrow base. Normally two types of bunds are practiced namely graded bunds and contour bunds. Graded bunds are used where rainfall is high and contour bunds are used where rainfall is low. The option of the type of the bunds depends on the slope, rainfall, soil type and the purpose of making the bund in the area. Contour bunds are constructed following the contour as directly as possible. A series of such bunds separate the area into strips and acts as barriers to the flow of water, thus reducing the quantity and velocity of the runoff. Graded bunds are used for safe disposal of surplus runoff in high rainfall areas and regions where the soil is moderately impervious. They could have a uniform grade or variable grade.
Other soil moisture conservation techniques can include rainwater harvesting to minimize runoff and collect water for use on site.
- The benefits of several soil moisture conservation methods, depending on the material used, may include better control of weeds, provision of additional nutrients to the soil, soil temperature manage and safety of the soil surface from the impacts of heavy rain and wind.
- Active reuse of waste organic materials reduces waste management needs, returning the residue crops and plants to the soil during decomposition.
- Potential to reduce water irrigation needs, increase crop productivity and develop soil quality
- By extension, reduced irrigation needs can also reduce the costs and energy requirements of water pumping for irrigation.