Introduction

Dry farming or dry land farming is the practice of crop production entirely with rain-water received during the crop season or on conserved soil moisture in low rainfall areas of arid and semi-arid climates and the crop may face mild to very severe moisture stress during their life cycle. Dry land farming is characterized by having:

1. limited rainfall less than 800 mm,

2. shortage of moisture availability,

3. growing season less than 200 days,

4. single crop or intercropping system and

5. having constrains of wind and water erosion.

Soil types in dryland areas

Five types of soils observed are black, alluvial, red (laterite and lateritic), sierozems and submontane soils. In the north and northwest of the country, alluvial, sierozemic and submontane soils predominate. In central and south India, black and red soils occupy the highest area. In the higher rainfall regions and coastal areas, the laterites and lateritic soils predominate.

1. Black soils

The black soils are deeper, clay to clay loam and characterised by low permeability and high water holding capacity. Low infiltration rate, high plasticity and stickiness, low organic matter content, high CEC, the calcareous nature and slightly alkaline reaction, pose problems of management practices, Vertisoils, when kept fallow during Kharif, are exposed to soil erosion hazards.

2. Red soils

The red soils are light textured, shallow to medium in depth and usually underlain by compact subsoil, fairly porous and low water holding capacity. Soils are prone to erosion and surface crusting. Because of crust formation run off Alfisols is more than in Vertisols. Crusting just after seeding results in the poor emergence of seedlings, particularly in the case of small seeded crops such as finger millet and pearl millet.

3. Alluviai soils

These soils are fairly level, deep, light to medium in texture with favourable physical characteristics and good permeability. Small showers are useful and there is the utilisation of most of the water held by the soil due to low moisture content at wilting point.

4. Sierozemic soils

Very deep alluvial sandy loams, low soil moisture storage, instability of soil structure, and poor soil fertility is the major problems of soil management in the desert ecosystem. High wind velocity leads to servere wind erosion. Soil drifting leads to soil and nutrient losses. Surface crust formation after sowing following light showers limits the desirable crop stand. These soils are observed in Dantiwada, Hisser and Jodhpur.

5. Submontane soils

Such soils are distributed in the dry subhumid environment of Hosiarpur in Punjab and Rakh Dhiansar in Jammu and Kashmir and in the humid tract of Dehradun. The lands are sloping, the soils range from loamy sands to sandy loams, silty loams and clay loams with soil moisture storage capacity improving in that order. Soil crusting occur in soils of dry and sub-humid regions.

Constraints

Edaphic Problems associated with dryland farm.

1. Poor and marginal lands with soils low in fertility and productivity;

2. Uneven topography with high erodability;

3. Difficulty in workability particularly in Vertisols;

4. Shallow or very deep in depth with extreme permeability;

5. Low moisture storage and release capacity particularly in Alfisols;

6. Presence of dissolved injurious salts in ground water;

7. Problem soils with respect to soil reaction (pH) and high concentration of soluble salts in the surface soils;

8. Water logging in level lands; flooding and breaking small field bunds resulting in poor conservation of soil and water;

9. Movement of sand and soil;

10. High surface crusting that leads to poor crop stand and high cracking to a high rate of evaporation and mechanical injury to roots.

Reduction of moisture loss due to Evaporation and Transpiration

Following measures are taken to reduce the loss of moisture received by the soil.

1. growing early maturing adaptable crop varieties with a deep and ramified root system and with a reduced number, size and horizontally orientation of leaves.

2. maintaining optimum plant population per unit area.

3. sowing crops either in dry soil anticipating rainfall suitable for early crop establishment with the first shower, and subsequent growth and development with subsequent rainfall, or in optimum soil moisture but with a minimum expenditure of seasonal moisture for land preparation and sowing;

4. keeping the field free from weeds,

5. adoption mixed or intercropping to utilise the slow growth phase of wide spaced crops, to restore soil fertility and to check soil and water loss,

6. using mulches,

7. using agri-chemicals;e.g. anti-transpirants, plant modifiers or growth retardants, desiccants or defoliants, crop ripeners, anti-evaporants, antiseepage.

Cropping systems

Cropping systems differ according to climate and soil types. The areas with 400 to 750 mm annual rainfall, mono cropping with traditional long duration crops is common. Generally adaptable crops are cercals, oil-seeds, pulses.

When the rainfall is between 500 to 700 mm with a distinct period of moisture surplus, the intercropping system can be adopted. Intercropping facilitates the growing of either cereal + legume or legume + legume. e.g. are: sorghum + pigeonpea, pearl millet + pigeonpea, sorghum + green gram, sorghum + soybean, groundnut + pigeonpea and foxtail millet + pigeonpea.

In areas with more than 750 mm annual rainfall with a soil storage capacity of 150 mm or more of available moisture sequential cropping is possible. e.g. pulses and oil-seeds, rice followed by chick-pea, maize followed by chick-pea, sorghum or green gram followed by safflower or sorghum- chick-pea and maize-chick-pea.

1. These break up the slope.

2. Intercept runoff before its volume and velocity become sufficient to cause serious erosion

3. gives more time for infiltration

4. water is diverted into the channels down safe gradients of suitable discharge or outlet points which carry away water in such a way as to minimize erosion damage to other land and

5. Finally leading to better conservation of run-off water for agriculture.

• Methods

1. Contour bunding

The bund section is 1.61 m² in Vertisols and 1.05 m² in Alfisols. The vertical distance is about 0.9 m. The area occupied is upto 5.0 per cent by the bund and the area lost from cultivation due to stagnation in Vertisols would be 10 to 15 per cent.

2. Graded bunding

Graded bunds are of 0.8 m² cross section in Vertisols and at vertical internal of 0.7m with a channel on the upstream side. The area lost due to the structure would be not more than 3-5 per cent and there would be no water stagnation and graded bund with grassed waterways and box-type masonry drainage outlets in arable fields.

3. Tie-ridging

The practice of tie-ridging, where adjacent ridges are joined at regular intervals by barriers or ties of the same height, allows the water to infiltrate and prevent run-off except during intense storms. This method is adequate in moderate rainfall areas, except on very steep slopes.

4. Bench terracing

On steeply sloping lands, the slopes where such terraces are found useful vary from 6 to 30 per cent. Bench terraces with 100 m length, longitudinal grades in the range of 0.2 to 0.8 per cent are recommended for Alfisols of high rainfall regions.

5. Ploughing

Ploughing across the slope and growing low value crops in catchment areas, the ploughing of deep soils should be done once in three to four years immediately after rabi crops. The light, shallow and medium soils should be hoed instead of ploughing which help to receive and retain moisture.

6. Reclaiming problem soils

Reclaimation of Acidic Alkaline and Saline soils should be reclaim by adding lime, gypsum, sulphur, or pyrites respectively. Growing high value crops in level run-off concentrated strips and incorporating a liberal quantity of organic matter.

Maintenance of soil fertility and yield stability

Dryland areas have low yields and high yield fluctuations. The maintenance of soil fertility is a problem in such areas as for a considerable period of the year the soil remains uncropped and there is a loss of plant nutrients, loss of the fertile surface due to erosion leads to a decline in soil fertility to build up soil fertility and reduce the fluctuation of crop yield.

1. the combined use of farmyard manure and green manure with inorganic fertiliser,

2. the incorporation of crop residues,

3. the inclusion of fodder-legumes/legumes in the cropping system/rotation,

4. the use of bio-fertilisers,

5. suitable methods of application of fertilisers, and mulching ,

6. checking loss of surface soil by using soil stabiliser and chemicals e.g. Na₂,Co₂,polythene sheet, mulches and plastic sheets.

7. developing small agricultural watersheds for run off collection and recycling for life saving irrigation to crops in moisture stress,

8. allowing a portion of the holding as chemical or legume fallow which on cultivation provides a substantial yield during famine,

9. adopting alternate land use planning in conjunction with regular cropping to improve the income of the farming families from fibre, fuel, fruit, furniture-timber, fodder and farm animals along with food.

Conservation of soil and water in dryland areas are inter-related and where one is tried the other is also achieved.

Ag.
Technologies
(Soil Magt.)