Land and Water Management Practices in Semi-Arid Regions | India

After reading this article you will learn about the land and water management practices in semi-arid regions of India.

Land and water management practices for raising successful crop in any region depends not only on the climate but also on prevailing moisture content in the soil. Thornthwaites’ moisture index is used to identify the broad climatic zones from the view point of crop production practices.

Krishnan and Singh (1969) calculated the moisture deficit index based on the precipitation (P) and potential evapotranspiration (PE) using the formula: (P – PE/PE) x 100 and thus divided the whole country into 8 zones.

The zone 3 forms the core of the semi-arid region where rainfall is between 500 and 900 mm and moisture deficit index is – 40 to – 60.

The semi-arid areas cover about one-third of India and include north-western and western Madhya Pradesh, Marathwada and Vidarbha regions of Maharashtra, Telangana region and central parts of Andhra Pradesh, most of Saurashtra (except the extreme west and Rann of Kutch), Tamil Nadu, Karnataka (except some arid pockets in central parts), southern Rajasthan, eastern Haryana and western Uttar Pradesh.

The rainy season is short in semi-arid regions. The rains are also seasonal and erratic, highly variable in time and space resulting in excess of water during a part of the year and acute deficiency during rest of the year.

Thus, soil mois­ture is the most relevant factor for agriculture and aridity puts a severe limit on all biological productivity. The problem of rain water management centres on drainage of excess water and its storage for use, as and when required, for rais­ing the crops.

Black, red and alluvial soils are the predominant soil types in semi-arid zone. Black soils are formed by weathering of basalt rocks either formed in situ where they are shallow to medium deep or transported with water where they are deep to very deep.

Red soils are formed by weathering of granite and gneiss rocks and are comparatively shallow. Alluvial soils are a part of the great Indo-gangetic plain in north-western Madhya Pradesh, western Uttar Pradesh and eastern Haryana.

Problems of Soil and Water Management in Semi-Arid Areas:

The semi-arid tropics, where precipitation exceeds the potential evapotranspiration for 2 to 7 months represents diversity of soil and climate. The area is characterised by soils low in organic matter and fer­tility and by undependable rainfall.

In most areas of semi-arid, the average annual rainfall would appear to be sufficient for one or in many cases for two good crops per year; however, the rainfall patterns are erratic and undepen­dable with frequent rainless period even within the rainy season. Much of the rain occurs in high intensity storms resulting in runoff and severe erosion.

These areas are always under the threat of scarcity of water and frequent and prolonged drought due to uncertainty and insufficient rains. The primary con­straints to agricultural production are the lack of soil moisture and its proper management.

The gullies are also formed in semi-arid areas which need soil conservation measures. Our chief concern in semi-arid areas is to conserve and protect soil and water and obtain sustained economic yield making most efficient use of conserved moisture.

Soil and Water Losses in Semi-arid Areas:

Black soils have enormous capacity for surface moisture storage and conse­quently very little runoff. However, soil is liable to be eroded when it is brought under cultivation. The rate of infiltration is reduced considerably and soil be­comes almost impervious under saturated conditions when even light showers result in runoff and tend to cause soil erosion.

The erosion is more con­spicuous on clean cultivated fields because most of the vertisols are kept fallow during rainy season. Red and alluvial soils have comparatively high rates of infiltration but once runoff occurs they become very susceptible to erosion, particularly where slope is more than 0.8%.

In semi-arid areas, there are many heavy rains which are in excess of the capacity of the soil to absorb. It has been observed that 20-30% of rainfall received is lost as runoff and leads to soil loss in the range of 15 to 81 tonnes/ha (Table 8.1).

Soil erosion depends upon the land slope and cover conditions. Sheet erosion is of common occurrence even on slopes less than 8% while rills, washes and gullies of varying sizes are formed on soils having more than 0.8% slope without vegetative cover.

Detailed studies were conducted at Dehradun to evaluate soil and water losses under various land uses; tillage operations and rotations. Maximum water loss occurred under bare fallow plot whereas maxi­mum soil loss was observed from bare ploughed plot (Table 8.2).

This was true for both monsoon and winter rains. Natural grasses and doob grass (Cynodon dactylon) proved to be the most effective in conservation of soil and water.

Cultivated crops, in general, give more soil and water losses than natural cover and grasses. Tobacco, jowar and maize being clean cultivated crops give greater soil and water losses as compared to close growing legumes such as cowpea, groundnut and mung. Legumes, in general, provide better soil cover than clean cultivated crops (Table 8.3).

Management Practices in Semi-Arid Zones:

1. Land Use Planning:

On flat lands, with less than 0.3% slope, water logging or water stagnation are more serious problems than erosion, particularly on deep black soils which have low infiltration capacity.

Sheet erosion is common on slopes less than 0.8% whereas rills, washes and gully are problem on soils with slopes more than 0.8%. Before applying any land treatment the land should be put to crops ac­cording to its suitability as shown in Table 8.4.

2. Planning for Rainfall Utilization:

The best use of natural rains in the semi-arid areas is done, firstly by increasing intake of rain and reducing runoff, secondly, by reducing intake and increasing runoff to a convenient point where water can be stored.

Thirdly, by reducing the loss of water in the process of evapotranspiration and fourthly by making best use of stored water either in cultivable field or in a pond. These 4 techni­ques are discussed in detail as below.

A. Increasing Intake of Rain:

The moisture status of the soil may be increased by increasing the rate of intake in the soil. A question naturally arises as to how to permit rapid and maximum penetration of rain water to the sub-soil region where it gets stored for future use through plant roots. This is possible by leveling and bunding, deep plough­ing during summer, altering planting pattern and stubble mulching.

i. Leveling and Bunding:

In semi-arid areas, open field cultivation is generally practiced. In this system, fields are cultivated throughout the monsoon season when soil moisture per­mits tilling of soil to create loose soil on the surface to serve as “soil mulch” till the sowing of the winter crop in the succeeding season.

Since fields are not bunded in this system there is considerable loss of water which could have otherwise been avoided, provided fields were bunded. It has been shown by various researchers that in these fields bunding conserves soil and rain water very effectively.

The beneficial effects of soil moisture conservation through bunding and levelling of land have been extensively demonstrated in the semi- arid alluvial plains of Uttar Pradesh where 35,63 and 98% increase in yield has been obtained by bunding alone, levelling alone, and bunding cum levelling, respectively.

For soils having a slope greater than 0.8% but less than 6%, construction of graded bunds across the slope on a grade of 0.1 to 0.2%, spaced at vertical interval as given below, has been found beneficial (Table 8.6).

Soils with slope greater than 6% are highly susceptible to erosion. Such soils should be provided with bench terracing and used for growing trees and grasses.

ii. Water Diversion Bund:

To avoid serious soil erosion, it is essential to construct water diversion bunds. A water diversion bund is the first line of defence in soil conservation work to prevent the outside water from running through the field.

A water diversion bund is essentially a graded bund with a shaped drainage channel along it on a grade of 0.2 to 0.3%. The cross-section of the bund depends on the area whose water is to be diverted and on the rate of runoff. The base width of water diver­sion bunds for different areas of catchment is given in Table 8.7.

(a) Grassed Waterways:

Water ways should be constructed to drain excess runoff to a safe and suitable site. The cross-section of a waterway is calculated on the basis of runoff rate, the total catchment area and the value of permissible velocity of the flowing water which depends on the nature of the bed.

If the bed of waterway is too steep, it gets corroded when the velocity of water exceeds 0.5 m/sec for bare sandy soil, 1.0 m/sec for bare clay soil; 1.4 m/sec for grassed soil and murrum (weathered rock). In such situations the beds of waterway need to be stabilized by construction of appropriate gabion structure at proper points.

(b) Deep Ploughing during Summer:

Deep ploughing during summer particularly in soils with slowly permeable sub­soil layer has been found to increase moisture storage in the root zone and consequently the yield. Kanwar (1968) reported that deep ploughing to 30 cm where subsoil had slowly permeable layer at Ambala and Ludhiana increased the moisture storage in soil and enhanced wheat yield by 14%.

(c) Stubble Mulching:

In stubble mulching, crops are cut at certain height above the ground surface and left in the field so as to maintain a cover on soil. Stubbles retard the velocity of flowing water on soil surface and thus permit greater time for intake of water in the soil.

Thus, it increases moisture in the soil. Kanwar (1968) reported that incorporation of rice husk at the rate of 62.5 tonnes/ha was found to improve the moisture status and consequently yield of wheat significantly.

(d) Altering Planting Pattern:

In low rainfall areas where plant often experiences moisture stress, particularly during a long dry spell, the technique of planting ‘narrow’ ‘ridge-furrow’ method has been found beneficial in making good use of rain water. In this system kharif crops are planted on ridges and rabi crops are planted in furrows subsequently in the winter season.

Ridges serve as a micro-catchment for fur­rows where rainfall accumulates. Water collected in furrows meets the water need at crucial periods of plant life and also ensures better aeration for crop planted on ridges during the kharif season. After harvesting of kharif crops, rabi crops are planted in furrows where sufficient moisture has been stored for germination of rabi crops.

The other method is broad ridge or bedding system. This is suitable for relatively high rainfall areas. On black soils the crop generally fails or yields poorly because of excess of moisture in the root zone.

To drain excess water and provide sufficient aeration broad ridges are constructed flanked by fur­rows on both the sides to support the contention that ridge and furrow system can be used to manipulate runoff and reduce erosion.

Work at International Crop Research Institute for semi-arid tropics and at the Indore Centre of the All India Coordinated Research Project on Dry Land Agriculture has shown that 90 to 240 cm broad ridges, depending upon crop and rows, made with tool bar attached with furrow opener are easier to maintain and work satisfactorily.

B. Reducing Intake Rate and Increasing Runoff (Water Harvesting):

Owing to low rainfall and erratic distribution of rainfall, the crops in semi-arid areas suffer due to moisture deficit at critical stages of crop leading to low crop yields or sometime complete failure of the crops. Under such situations it is better to increase runoff of rain water and collect at a convenient point for use by crops at most critical stage rather than spreading water thinly over large surfaces of land.

This is called water harvesting. Water harvesting consists of using rain water derived from an area that has been treated to increase runoff, in order to supplement soil moisture in the adjacent areas situated at a lower elevation.

Three systems of water harvesting are generally in vague:

(1) Inter- row water harvesting;

(2) Inter plot harvesting; and

(3) Collecting and storing water in pond.

(1) Inter-Row Water Harvesting:

In low rainfall areas water is collected in already opened furrows rather than evenly distributing the rainfall in order to increase moisture content for raising crops. This technique is also used to drain excess water and to provide aeration to growing crops in high rainfall areas.

Water stored in furrows is easily avail­able to crops. Experiments at International Crop Research Institute for Semi- arid Tropics and under All India Coordinated Project on Dry Land have indicated that inter-row water harvesting is quite useful for raising yield levels in semi-arid areas.

(2) Inter-Plot Harvesting:

In drought prone areas, it may not be only feasible but also desirable to leave a part of land for water harvesting and a part for cropping. The first portion, which is relatively elevated, is used for conveying water is runoff plot and the other one, which receives the runoff water (relatively low land), is called run-on plot.

Experiments at Central Arid Zone Research Institute, Jodhpur have shown that total production by cropping only 2/3 of the field (leaving one third) by adapting runoff farming is the same as obtained from cropping the whole field.

(3) Collecting Water in Field Ponds:

In semi-arid areas the rain water harvested from a part of the field should be collected and stored. Large quantities of runoff can be collected and stored by providing slope to collect hillside runoff, by modifying vegetation, by treating the soil surface to reduce infiltration rate or covering the soil with impermeable coating.

Sodium salts are used to disperse the soil particles so as to reduce infiltration rate and increase runoff volume. Covering the soil with plastic and metal films or rubber sheeting or spraying with asphalt are some of the promis­ing methods of increasing water yield from watershed and using it later as life-saving irrigation for raising successful crops.

C. Reducing Evapotranspiration:

Since evapotranspiration (ET) exceeds the total annual rainfall in semi-arid regions, attempts should be made to cut down evaporation from soil surface by mulching and ploughing the field from time to time, and by reducing transpiration through anti-transpirants, early harvesting of kharif crops and weed control.

(1) Use of Anti-Transpirants:

Transpiration from crop surfaces can be reduced by using anti-transpirants. Anti-transpirants are of 4 types viz., stomatal closing, film forming, reflectant and growth retardant type. Stomatal closure types close the stomata after their application and thus would affect photosynthesis.

Therefore, choice would fall on the chemicals which decrease transpiration to a greater degree than photosynthesis. The most extensively used chemical is phenyl mercuric acetate (PMA). Waxy materials that cover the stomata with a thin film create more resistance to passage of water than carbon dioxide.

A new approach on reducing transpiration by application of reflectant such as kaoline water emulsion on crop canopies has also been found useful. This emulsion increases leaf albedo and grain yield.

(2) Weed Control:

Controlling weeds has been known to be one of the most effective means of increasing amount of available water to crops. Weeds compete with crops for soil moisture, along with other factors of crop production and transpire greater amount of water per unit of dry matter produced, than the crop. The rewards for your labour and cost incurred in growing a crop will not be forthcoming if weeds are not controlled.

Weeds are wasteful and reduce crop yield to un­believable low levels. Timely weed control, as such, assumes special sig­nificance in rainfed areas. The first 30 days are most crucial for weed control in kharif crops.

It should be restored to within 30 days in pearl millet and within 20 days in mungbean. Weed control thereafter is of little use, as the damage already done in irreversible. Some results on the effect of weed control has been shown in Table 8.8.

(3) Mulching:

Mulches affect soil water balance through runoff control, increased infiltration, decreased evaporation, weed control, soil temperature through radiation shielding, heat conduction and trapping and evaporative cooling. For semi-arid areas soil moisture and temperature are of greatest importance.

Where precipitation is limited and erratic and evaporation is high, good yields are ob­tained if precipitation is conserved effectively. Although plastic films generally resulted in higher water conservation, they are relatively expensive and difficult to manage under large scale field condition.

Crop residues and other plant waste products such as straw, Stover, saw dust and woodchips have been suggested as mulch materials. These materials are cheap and most often readily available and encourage infiltration.

Mulch­ing is generally associated with moisture conservation by reducing the surface evaporation. The influence of mulch on moisture conservation depends upon the kind of mulch used, the extent of surface covered and the rate of mulch material, soil moisture status and water table depth.

Studies at Kota showed the effectiveness of cultural mulch, jowar stalk mulch, dry grass mulch and polythene mulch in increasing the grain yield of wheat. Soil moisture determination made at fortnightly intervals showed that the soil with mulch treatments had relatively higher percentage of moisture than soil with no mulch.

Effects of surface mulches at Dehradun showed that mulching with 5 tonnes of grass per hectare during October-November, after the harvest of the preceding maize and before the planting of wheat, proved most effective in conserving soil water for wheat crop.

Normal tillage + grass mulch at the rate of 4 tonnes/ha in between rows of maize grown on 8% slope at Dehradun sig­nificantly reduced the soil loss from 52 to 9 tonnes/ha and runoff from 52 to 25%. Stubble mulches have proved more effective in reducing soil water loss and increasing organic matter content of the soil.

(4) Tillage:

Since precipitation is limited and evaporation potential is high, attempts are made to conserve moisture by reducing evaporation. The various mulches, may be tried wherever feasible.

Since crop residue produc­tion in dry areas is inadequate to result substantial soil moisture conservation, ‘soil mulch’ created as a consequence of repeated ploughing is more practical in dry areas. The soil mulch or dust mulch breaks the continuity of capillary pore or subsoil to surface soil thereby reducing the evaporation losses.

(5) Timely Harvesting of Kharif crops:

Kharif crops are generally harvested when over ripened. This allows soil mois­ture losses to the extent that does not permit even preparation of field for rabi sowing. It would be advisable to harvest crops at physiological maturity rather than delaying harvesting till complete drying of plant stem and other plant parts.

Harvesting at physiological maturity not only facilitates the early field preparation and moisture conservation but also does not affect yield adversely. Early harvesting facilitates seeding of rabi crops on conserved moisture.

D. Efficient Use of Conserved Moisture:

Efficient utilisation of conserved soil moisture is essential for increased production in semi-arid areas. Following practices may be adapted for in­creasing efficiency of conserved moisture.

(1) Selection of crops and their Varieties:

The amount and depth of moisture conserved is not uniform throughout the semi-arid regions. This varies with the amount and distribution of rainfall and water holding capacity of the soil. The amount of stored soil moisture deter­ mines the water availability period or length of growing season which in turn would decide the choice of crops and their varieties to be grown in a particular region.

Based on the length of growing season available in each region Table 8.9 presents a list of suggested crops and their varieties to be grown for effi­cient utilisation of moisture and increased yield.

The crops selected for semi-arid should be:

(i) Of short duration;

(ii) Of low water requirement;

(iii) Responsive to agronomic inputs;

(iv) Able to escape drought;

(v) High-yielding; and

(vi) Deep rooting system.

2. Mixed Cropping:

Mixed cropping offers a more effective and continuous cover of land, thereby preventing soil erosion. The roots of the various mixed crop components feed at different soil depths leading to more efficient exploitation of soil water and soil fertility.

Under dry farming conditions of arid and semi-arid regions of India, inter ­cropping is generally practiced. The inter-cropping is the best mechanism of exploiting the environment, minimising the risk. In semi-arid areas, pigeonpea + sorghum, groundnut + sorghum or millets, pigeonpea + groundnut are com­mon inter-crops.

The cropping systems, developed by farmers of dry areas, are based on several years and generations of experiences and therefore should be given due consideration before replacing with a new system of cropping.

Wheat and gram mixed cropping in alternate rows in rabi and cultivation of moong/urd/pigeonpea with bajra or jowar in kharif have been found to be more remunerative than pure cropping of the component crops at a number of loca­tions in North India. Feasibility of raising urd/moong between two rows of pigeonpea has also been proved.

Similarly, cultivation of soybean or urd be­tween two rows of ragi has been found to be remunerative under cainfed con­ditions of hills. Cultivation of one row of pigeonpea between two rows of maize in the broad bed and furrow systems on vertisols has also been found useful.

Studies at Kota have shown that soil and water losses from mixed cropping system of jowar + pigeonpea were much less compared to the pure cropping of urd or soybean. Turmeric and ginger were found to be the most suitable inter-crops in peach orchards at Dehradun. Studies at Bellary indicated the suitability of castor crop for mid-season correction when the sowing of main crop was delayed due to erratic rains.

3. Crop Rotation:

No rigid system of either continuous cropping or rotation has been devised that can equal a flexible cropping plan in economy of production in semi-arid region. Such a plan takes into consideration the soil moisture and fertility conditions of individual fields. Crops should be selected that will provide the maximum cover under these varying conditions.

Work at Vasad indicated that a two year rotation of green manured bidi tobacco-kodrattur mixture or sundia jowar under rainfed conditions has been found suitable. A rotation of bajra + mung – green manure – bidi tobacco has also been found economical.

Under rainfed conditions of Agra bajra + arhar-mustard rotation (2 years) was found to be most profitable in reclaimed ravine lands along the banks of Yamuna river. Bajra-cowpea was the next best rotation.

Selection of proper rotation will control erosion, lessen soil loss and preserve soil productivity. A good rotation should include a cultivated row crop, densely planted small grains and spreading legume, or a grass legume mixture.

Naturally, the actual choice of rotation crop in very tract will be based on land use capability, climate, economic condition, soil type, slope, character and degree of erosion and other physical and chemical properties of soils.

‘Maize-wheat’ and ‘Maize-peas’ and ‘Maize-gram’ have been found to be most remunerative crop sequences under rainfed conditions of Doon Valley. For U.P. Hills, ‘rice-wheat’ under irrigated conditions and ‘ragi-fallow-rice- wheat’ under rainfed conditions were found to be promising crop sequences.

At Ootacamund, where potato is grown in bench terraces, ‘potato-potato’ and ‘potato-peas’ were found to be most remunerative sequences.

Deep vertisols (black soil) are normally not cropped during the rainy season. However, by timely tillage during the dry season, dry planting of crops such as sorghum, pigeonpea and maize just before the monsoon rains has been successful at ICRISAT, Hyderabad. Dry planting on alfisols (red soil), how­ever, is risky because of their low water retention capacity.

Deep vertisols when fallowed during the rainy season lost 5-7 times more soil as compared to cropped watershed. Sequential cropping of ‘Maize-gram’ or ‘Jowar-gram’ is now feasible in the deep vertisols even under rainfed conditions. This practice in alfisols is possible only with irrigation since crops in such soils cannot be grown successfully without irrigation in the post-monsoon season.

4. Adjustment of Sowing Time:

The sowing time of kharif crops has to be so adjusted that flowering and fruit­ing, which are considered to be most crucial, coincide with periods of adequate moisture availability in the soil profile.

In general, early planting of kharif crops is advantageous from the point of better stand establishment, better use of available soil moisture and nutrient, less incidence of diseases and pests, early vacation of field for succeeding crop in a double cropping system.

Late sowing may coincide with moisture stress towards the end of the season, thus resulting in low crop yields. Early planting, by first week of July at Varanasi, of upland rice, at Bhubaneswar of red gram, castor and ragi, and at Jhansi of sorghum, resulted in higher yields of grain than late planting.

Dry sowing of kharif crops in anticipation of rains is an attempt to give an early start to the crop. Dry seeding has limitation in heavy soils where crusting is a serious problem.

Cotton planting 3-4 weeks prior to monsoon arrival is a common practice in cotton growing areas around Indore to give early start to the crop. Similarly, rice seeding much before the commencement of monsoon is quite common in hill areas of Uttar Pradesh.

5. Tillage:

Tillage is no doubt essential for seed bed preparation and weed control, incor­poration of crop residues in soil, and improvement of water intake by the soil. But excessive tillage, on the contrary, may lead to accelerated soil and water loss, soil compaction, loss of organic matter and moisture and deterioration of soil structure apart from added cost.

Minimum tillage practices in conjunction with chemical weed control would be desirable to protect soil erosion. Contour tillage would prove very effective in minimising the soil and water losses from slopy lands.

Quite often, farmers perform too many operations for seedbed preparations which is neither essen­tial nor desirable which may in-fact erode the soil. It is now being increasingly recognised that minimum tillage should be done in arid areas so as to avoid any soil and water losses.

6. Plant Population Requirements:

Short duration, short statured varieties and varieties with compact and erect growth habit, in general, give higher yield with denser plant stand. However, plant population to be maintained needs to be tailored looking into the soil moisture storage in the profile and supplemental rainfall and irrigation.

Wider spacings and lower plant populations are generally recommended for grain crops grown in rabi season under un-irrigated conditions. In the eventuality of the failure of winter rains, a mid-season correction could be made by thinning the plant stand. Higher plant population may prove disastrous as it would lead to early exhaustion of stored soil water much ahead of the crucial grain filling stage of the crop.

Studies at Dehradun showed that maize crop grown in rows on 4% slope, across the slope, gave better performance when the row spacing was increased from 45 to 90 cm, and plant spacing within the row narrowed down from 40 to 20 cm, keeping the plant population level constant. This planting geometry reduced runoff loss from 45 to 32% and brought down the soil loss from 22.3 to 14.2 tonnes/ha.

7. Use of Manures and Fertilisers:

Balanced use of plant nutrients is essential for higher crop productivity. Or­ganic manures such as farm yard manures, compost, green manures and incor­poration of crop residues have proved useful in restoring soil productivity particularly in degraded soils.

Organic manures not only supply major plant nutrients like N, P and K but also supply essential micro-nutrients and improve the physical conditions and water holding capacity of the soil.

Organic manures, such as farm yard manure should be thoroughly incorporated into the soil well before the planting of the next crop at rates ranging between 5 to 10 tonnes/ha. Deep placement of fertilisers in the moist zone is recommended in the semi-arid tracts. Nitrogen @ 15-20 kg N/ha should be applied to the wheat crop through foliar sprays of urea during the pre-flowering stage.

Top dress­ing, of 15-20 kg N/ha would prove useful for rainy season crops like bajra, jowar, rice and ragi grown under rainfed situations. Split application of nitrogen leads to greater recovery of applied fertiliser nitrogen for all rainy season crops. Zinc deficiency could be corrected using zinc sulphate spray @ 5 kg zinc sulphate/ha.

Alternatively 20 kg zinc sulphate could be applied to soil at the time of planting as a basal dose. Grain and forage legumes should in­variably be treated with Rhizobium culture. An application of 40-60 kg/ha P2O5 at the time of planting of legumes, particularly in soils deficient in phosphorus, has been found to be useful.

8. Mid-Term Correction:

Due to uncertainty of rainfall in semi-arid areas, agricultural operation for crop production cannot be timely or rigidly followed. Some of the practices which are planned either due to failure of rains or due to occurrence of rains, though otherwise were not planned, called mid-term correction. For instance top dressing of nitrogenous fertilisers may be taken up if it rains, otherwise not.

Due to failure of monsoon farmers may like thinning the plants to the extent he feels soil moisture would be enough to mature the crop. In the eventuality of complete failure of monsoon during kharif season the farmer would like to har­dest the crop for fodder rather than waiting for grain setting.

9. Planning of Aberrant Weather:

Successful crop production is uncertain due to vagaries of monsoon in semi- arid areas. Uncertainty in monsoon may be due to either of the following types: late arrival of monsoon, early withdrawal of monsoon than normal time or long dry spell between the two rains.

In case of late commencement of monsoon, long duration crops should not be grown. Under such situations early maturing crops like urd bean, mungbean, till should be preferred. For instance, bajra should be planted under Varanasi conditions, if out-burst of monsoon is in the first week of August. Fodder crops may be grown if monsoon arrival is in the third week of August, alternatively field should be kept fallow.

If there is a long dry spell after planting of kharif crops life-saving irrigation should be given. Alternatively nursery of rice crop may be raised and planted after the rain showers are received. Plants should be thinned and gap filled after rains if possible.

In the eventuality of early withdrawal of monsoon, crops may be harvested for fodder rather than leaving the crop in the field for matur­ing. Under such situations of late rains moisture should be conserved for early planting of gram, sarson and lahi. Sunflower may also be planted early in rabi season because it can be planted at any time of the year.

However, these suggestions can be adapted if aberrations in monsoon are known well in advance. Unfortunately, this is not the case. In this connection a good knowledge of monsoon behaviour and their predictability is essential. A good deal of information on monsoon behaviour is required to plan for aber­rant weather.