Introduction

1. The principal areas of the arid tropics are in north Africa and an area of about 2 million square km in countries like Yeman, Saudi Arabia, Muscat, Mexico, India, and Australia.

2. The North Africa arid region is the most extensive region within the arid tropical zone (7.2 million sq. km).

3. Australia has most of the arid tropical land (14 million sq. km) in the southern hemisphere.

4. In North America, portions of southwest Mexico largest.

5. Rainfall distribution:

• Arid tropical Africa, rainfall decreases from south to north ranging from 500 mm at 11 degrees N to 200 mm at 15.5 degrees N.
• Australia, rainfall decreases from nearly 500 mm in north to about 250 mm at Tropic of Capricorn

• Accurate and reliable statistics on land use, crop distribution, and yields of crops for different climatic zones either don't exist or are not readily available
• The proportion of land in crops is small and land use and crop yields vary based on variations in rainfall, low soil fertility and disease and pests
• Inheritance laws favor fragmentation of individual holdings
• A high proportion of farmers rent/paid on a crop share basis
• Pastoralism is the age-old occupation and plays an important role because livestock is capable of using almost all the land
• Arid and semi-arid regions of world contain - 1/3 of sheep, 1/2 of cattle, and 2/3 of world?s goats

• Is next in importance to animal husbandry
• Crop production is low in productivity
• Crops grown are millet, pulses (mung) in India; in Africa, corn, cotton, and peanut

9. Crop production and animal husbandry are kept either totally separate or are inadequately associated.

10. One crop a year or one in two years is general pattern.

• Important for soil fertility restoration when there is no means of fertilizing soil
• Retain portions of water from two rainy seasons for one crop
• Fallow may leach excessive salts to lower horizons

12. Solar incidence increases crop water requirements which limits cropping and yields.

13. Drought combating strategies must be available for prolonged droughts (3-4 weeks) occurring in seedling states in 1 of 5 years.

14. At flowering and grain formation stages, 2 of 5 years.

15. Existing cropping patterns on rain-fed lands are traditional and subsistence-oriented.

The Approach

1. Amelioration of arid regions falling in the rainfall range of 300 mm and below can best be achieved by a silva-pastoral system with suitable tree species.

2. In areas receiving 300-400 mm of annual rainfall, improved cropping and animal husbandry technology for dry land crop production should be adopted.

• Selection of crops and varieties with growth patterns matching rainfall and possessing high moisture efficiency
• Selection of suitable crops and varieties for delayed onset of the monsoon
• Adjustment of sowing time to insure that the periods of flowering and grain filling coincide with the periods of adequate moisture availability
• Judicious fertilizer use
• Adoption of appropriate water-harvesting techniques
• Moisture conservation (mulches)
• Weed control and effective crop protection
• Harvesting of crops to impart stability in years of subnormal rainfall
• Nursery growing of millets and its transplanting is a valuable technique

• Tolerance to drought
• Mature early
• Should have high yield potentials

• Sowing so flowering and fruiting coincides with periods of moisture
• Under delayed onset of the monsoon, nursery-sowing and transplanting of millet recommended

• Fertilizer use in arid tropics is almost nonexistent, owing mainly to uncertain rainfall, the cultivation of non-responsive crop varieties, and inadequate scientific advice
• Appropriate fertilizer use technology assumes special importance in double-cropping systems feasible in years of high rainfall

• Water scarcity problems can be partially overcome by adopting and appropriate water harvesting system which can provide additional quantities of moisture
• Cropping only 2/3 of the field (leaving 1/3 for micro-catchments) with the use of runoff framing gives comparable production as obtained from conventional cropping on a flat surface
• Runoff farming has been found to offer potentials for increasing and stabilizing yields
• The modified inter-row water harvesting system induces an additional runoff in trenches from ridges and also from micro-catchments provided in between the trenches
• In the arid tropics, it may not only be feasible but desirable to set apart a portion of the land for water harvesting and provide a tank to collect and store runoff water

• Soil and moisture conservation programs are basic to any program of crop production in arid regions
• Wind action may be particularly serious during summers
• Stubble mulching and wind strip-cropping are basic remedies
• In arid regions, surface evaporation is as important as deep percolation, for once the surface soil dries up, it acts as a natural mulch against the loss of moisture through evaporation
• Quick drying of surface soil and excessive evaporation just after rainfall pose problems in seedling emergence and proper crop establishment
• Under such conditions, the use of a surface mulch is advantageous

• Weed control is most important within the first 30 days in the case of millet and 20 days in the case of mung
• Weeds should not be disturbed on lands lying fallow during winter until the first shower
• If the weeds are incorporated into the soil, the nutrients they extract are brought back to the soil and are available to the succeeding crop

1. Grasses are important in arid zones for soil improvements, fodder, and soil protection against wind erosion (improve physical condition of soil)

2. Legumes can be grown with advantage as intercrops with grasses (improve fertility from N fixation)

3. The use of non-monetary inputs in dryland agriculture.

• Simple practices such as seed soaking
• Growing crops in paired-row systems.
• Paired rows result in higher yields and better moisture-use efficiency than a uniform system in years of low or normal rainfall

1. Make detailed analysis of the climatic data and related information for the entire arid tropics.

2. Inventory natural resources (soil, land, vegetation).

3. Increase knowledge regarding plant types for intercropping and managing of intercropping systems.

4. Conduct tillage in relation to soil and nutrient conservation and crop establishment.

5. Practice organic recycling.

6. Collect and recycle runoff water.

7. Basic knowledge still lacking in:

• Crusting of soil and its control
• Moisture stress
• Movement of moisture
• Water balance