Selection of trees for arid agro-forestry

The arid regions of India cover an area of 317,090 km2and lies a 240-290 latitude and 700-760 longitude. The region is spread over seven states, viz., Rajasthan, Gujarat, Punjab, Harayana, Maharashtra, Karanataka and Andhra Pradesh, the north-western part of the country constituting almost 90% of the total arid zone area. Thus Rajasthan state alone accounts for 60% of the arid zone of India

The mean annual rainfall varies from 100 mm in the northwest to 450 mm in the eastern part of Rajasthan. Over 9% of the total Annual rainfall occur between June and September. The mean maximum temperature during the summer is 400C. The mean winter season temperature varies from 140C to 160C.

The potential evapotranspiration during summer is 7 to 9 mm/day, during the monsoon 5.3 to 6.4 mm/day and in winter ranges from 1.8 to 2.9 mm/day. Thus, the evapotranspiration far exceeds precipitation throughout most of the year.

High wind velocity is characteristics during summer and monsoon season throughout the northwestern arid zone. The wind speeds are minimum during the post monsoon period.

Selection of Tree Species

In the strategy of development of agro-forestry in arid zone of India, correct selection of trees is of prime importance. The tree crops should have following attributes:

  1. Since the water is a limiting factor in arids, the crop selected for arid region should have drought tolerance mechanism like,

  1. deep root system to draw water from deeper soil profile

  2. leaf shading in summer to conserve moisture.

  3. Water binding mechanism.

  4. Other xerophytic characteristics like wax coating hairiness, sunken and covered stomata on leaves to minimize the loss of water through transpiration.

  1. Tree crops in arid region should have tolerance to salinity and saline water and alkanity, which are common features of these areas.

The following tree and grass species are recommended for various desert regions.

Sandy plains: Tree species: Acacia tortilis, Prosopis juliflora, Prosopis cineraria, Albizia lebbek, Azadirachta indica, Acacia senegal, Tecomella undulata, Colophospermum mopane, Brasilettia mollis, Hardiwickia binata, Tamarix articulata, Cassia siamea, Eucalyptus camandulensis, Eucalyptus hybrid, Leucaena leucocephala. Grass species: Cenchrus ciliaris, Cenchrus setigerus.

Shallow soils: tree species: Acacia tortilis, Prosopis juliflora, Albizia lebbek, Azadirachta indica, Dichrostachys glomerata, Ailanthus excelsa, Holoptelea integrifolia, Zizyphus mauritiana, Eucalyptus terminalis etc. Grass species: Cenchrus ciliaris, Cenchrus setigerus, Dichanthium annulatum, Panicum antidotale etc.

Sandstone rocky sites: Tree species: Prosopis juliflora, Albizia lebbek, Butea monosperma, Acacia senegal, Commiphora wightti, Cassia auriculata, Angeissus pendula, Boswellia serrata etc. Grasses: Cenchrus ciliaris and Cenchrus setigerus.

Saline areas: Trees and shrubs: Salvadora oleoides, Salvadora persica, Tamarix auriculata, Prosopis juliflora, Prosopis tamarugo, Atriplex nummularia, Chenopodium auricosum etc. Grass species: Sporobolus species and Chloris species.

Shifting sand -dunes: Trees and shrubs: Acacia tortillis, Prosopis juliflora, Prosopis cineraria, Acacia senegal, Dichrostachys glomerata, Albizia lebbek, Tamarix articulate, Calligonum polygonoides etc. Grass species: Cenchrus ciliaris, Cenchrus setigerus, Sacharum munja, Lasiurus sindicus etc.

Horticultural fruit trees for arid areas: The following fruit trees are combined with silvicultural trees which form a silvihorticultural system of agroforestry: Zizyphus mauritiana, Punica granatum, Psidium guajava, Phoenix dactylifera, Aegle marmelos, Feronia limonia, Annona squamosa, Tamarindus indica, Salvadoro persica, Cordia myxa, Syzygium cumini, Emblica officinalis, Grewia asiatica, Carissa carandas.

Agricultural crops for arid areas: The following agricultural crops are combined with trees in arid areas: pearl-millet, cowpea, sorghum, cluster bean, black gram, green gram, moth, chick-pea etc.

Planting in arid areas: The best time to plant trees in arid areas is generally at the beginning of the rainy season, which is the period when other agricultural crops are also at their peak.

In arid semi-arid areas, moisture availability is a major limiting factor for successful establishment and early growth of trees. On sloping land the survival and establishment of the seedlings is particularly difficult because the little water available from rainfall tend to run off down the slope. Planting in sunken pits and triangular (V-shaped) and semi-circular bunds might improve the survival and growth rates of seedlings over normal planting pits under these conditions, due to increase water availability, reduced wind speed of reduced evapotranspiration.

 Agroforestry Systems in Arid Regions

Several agroforestry systems are suitable for arid and semi-arid regions. The most common AF system is scattered trees in agricultural/cultivated fields, constituting and agrosilvicultural system. This followed by boundary plantation of all species for shelter. However, the most popular agroforestry system is scattered trees followed by block energy plantation and boundary planting especially of shelter-belts, wind breaks and hedges.

An arid zone is characterized by hostile climatic conditions and hence several independent AF systems are practiced in this region to combat these vagaries. Some improved AF practices have been suggested to better the situation, such as sand dune stabilization, shelter-belt plantation, silvopastoral and agrosilvicultural systems, wind-breaks, and boundary plantation. They could be suitably practiced based on situation, purpose and need.


Ag.
Technologies
(Agro Forestry)