Water Conservation : Broad Bed and Furrow System (BBF)

Rainfed farming in semiarid tract is a risky enterprise. Fluctuations in timing of onset of monsoon, erratic rain distribution during the crop season, sudden occurrence of high intensity rain storms and absence of in-situ water harvesting systems are major constraints in crop production in these areas. Although the amount and timings of precipitation received by crop cannot be altered but proper management of its utilization can improve crop yields.

In irrigated farming, planting on flat lands and flood irrigation are commonly used practices. Main problems associated with such practices include higher input use (such as irrigation water, fertilizer, manpower etc.), declining water table because of over exploitation of ground water resources for irrigation, greater downward movement of water fertilizer and pesticide below root zone. higher pest incidence and poor control of weeds and diseases. Thus in irrigated farming also, although intensive agriculture has brought substantial enhancement in production of food grains but it has threatened the environment safety and promoted' the degradation and inefficient use of basic resources such as land, water and fertilizer. Hence there is a need to manage both rain and irrigation water efficiently by adopting appropriate soil management technology.

Broad Bed and Furrow System (BBF)

The Broad Bed and Furrow system has been mainly developed at the International Crops Research Institute for the Semi-arid Tropics (ICRISAT) in India. A comprehensive research programme was carried out on-station for eight years before being taken for on-farm adaptive research at Tadthanapalle in Medac district. It is a modern version of the very old concept of encouraging controlled surface drainage by forming the soil surface into beds. In medieval times in Britain this was used for improving pastures and called "rigg and furrow".

The recommended ICRISAT system consists of broad beds about 100 cm wide separated by sunken furrows about 50 cm wide. The preferred slope along the furrow is between 0.4 and 0.8 percent on vertisols. Two, three, or four rows of crop can be grown on the broad bed, and the bed width and crop geometry can be varied to suit the cultivation and planting equipment. 

In India the system has been used mainly on deep vertisols (heavy black clay soils sometimes called cotton soils); wide beds are used on a gentle grade and they are formed by ox-drawn wheeled tool carriers. 

Image courtesy : TNAU

Objectives:

(a)     To encourage moisture storage in the soil profile. Deep vertisols may have soil moisture storage up to 250 mm, which is sufficient to support plants through mid-season or late-season spells of drought. The possibility is also increased of double cropping by means of inter-cropping or sequential cropping. The large water storage capacity of the soil supports growth more easily during the subsequent dry but cooler post-rainy season.


(b)     To dispose safely of surplus surface run-off without causing erosion.


(c)     To provide a better drained and more easily cultivated soil in the beds. There is only a narrow range of moisture conditions during which the soil can be efficiently tilled or planted, and timeliness is a key factor. Only about 20 percent of the deep vertisols in India are cropped during the rains, mainly because of poor workability when wet.  If a crop can be established during the early rains, the profile is usually near saturation only for short periods during the latter half of the season, water is more efficiently utilized, and there is less need for run-off collection and storage. The possibility is also increased of double cropping by means of inter-cropping or sequential cropping. Tillage of the raised beds may be possible before the rains, introducing the possibility of dry seeding ahead of the rains in areas where the start of the rainy season is fairly reliable, and there is a good chance of follow-up rains to ensure the establishment of the germinating crop. The difficulty of preparing a seed bed during the dry season in these hard clay soils has been greatly improved by the use of broad beds and animal-drawn equipment.


(d)     The possibility of the re-use of run-off stored in small tanks . Small amounts of life-saving irrigation applications can be very effective in dry spells during the rains, particularly on soils with lower storage capacity than the deep vertisols.

The BBF system is particularly suitable for the vertisols. The technique works best on deep black soils in areas with dependable rainfall averaging 750 mm or more. It has not been as productive in areas of less dependable rainfall, or on alfisols or shallower black soils - although in the latter cases more productivity is achieved than with traditional farming methods. Other methods, with more emphasis on storage and irrigation within a package which includes BBF, are more likely to be viable for the alfisols. It is also stressed throughout the ICRISAT research that the BBF system should not be considered in isolation, but only as part of an improved farming systems package.

An important component of the system is an ox-drawn wheeled tool bar, which can be used with ridgers to form the raised bed and also later for carrying precision seeders or planters. The tool carrier is thus used for the initial forming of the beds, the subsequent annual reshaping, and for all tillage, planting, and inter-row cultivation.

source :  fao.org

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