In the arid region with low and erratic rainfall, high temperature and unfavourable soil conditions pose severe restrictions on the use of land for arable cropping. In the rainfall zone of less than 250 mm, silvi-pasture, pasture, horti-pastoral and silviculture rather than arable cropping has been regarded as best systems for soil management and better production.
In the rainfall zone of 250-500 mm, the dune complex, hardpan, shallow gravelly uplands and salt affected soils qualify for land use capability classification class VI and VII, which suggest that these areas are mainly suited for the above systems.
The crop husbandry is risky owing to poor yields and could deteriorate the soil quality further. Thus, grasses/legumes/alternate agriculture-based land use systems may be the better alternative for management of arid soils and sustainable production as these alternate systems reduce risk of further soil degradation of such fragile environment while preserving natural resources and soil quality.
System # 1. Grasses-Legume Mixture for Arid Region Soils:
Introduction of legumes in grassland serves manifold purposes. Intercropping of pasture legumes increase the soil fertility as it accumulates atmospheric nitrogen into roots. Legume requires comparatively less nitrogen from soil for growth and development. Moreover, nitrogen supply from soil is enhanced to the grasses in grass + legume mixed swards.
Thus, intercropping of grasses and legumes may be used for soil management and also for improving the fertility status of soil. Van et al. (2010) reported that grassland systems with a mixture of L. perenne and F. arundinacea are more sustainable than the monocultures of each, in terms of reduction of nitrogen losses and the build-up of soil organic matter.
System # 2. Wind Break and Shelterbelt for Controlling Soil Erosion in Arid Region:
Wind break is any type of barrier used for protection from winds while shelterbelt is barrier longer than wind break, usually consisting of trees and shrubs. The importance and utility of shelterbelt in checking the wind erosion has been well recognized. Considerable work has been done on the plantation of trees as wind breaks and shelterbelts.
The effectiveness of shelterbelts in reducing the wind velocity depends on velocity and direction of winds and also on canopy growth, design and geometry of shelterbelts. Kaul (1964) successfully used Prosopis juliflora, Azadirachta indica and Albizzia lebbek as three row shelterbelt along the highways in western Rajasthan. Five rows of shelterbelt in pyramidal shape were found to be suitable in desert areas.
The per cent reduction in mean wind speed by 8 years old, 5 m tall shelterbelts of Prosopis juliflora, Cassia siamea and Acasia tortilis was maximum at 2H distance. The reduction in wind speed by all the three shelterbelts during monsoon was higher than in summer possibly due to better canopy growth.
The use of shelterbelts also brought about 50% reductions in wind erosion. A mean loss of 546.8 kg ha-1 soil from bare field reduced to 351, 300 and 184 kg ha-1 in shelterbelts of Prosopis juliflora, Cassia siamea and Acacia tortilis, respectively. The total nutrient loss was also found to be maximum from bare soil without shelterbelts followed Prosopis juliflora, Acacia tortilis and Cassia siamea thereby improving soil fertility by the introduction of shelterbelts.
System # 3. Silvi-Pastoral System in Ravine Land Reclamation:
Degraded ravine lands in Rajasthan and Gujarat are vulnerable to soil erosion and fast depletion of their vegetation cover. Chinnamani (1992) in Mahi ravine lands in Gujarat revealed manifold increase in forage production under rainfed condition by using different combinations of top feed tree and grass species. In denuded ravines, introduction of trees and grasses under intensive care and adopting soil conservation measures like gully control, diversion bund, check dams, contour trenches and bunds provide good establishment in 2 to 6 years.
This was followed by protection from biotic factors by providing fencing and closures. This brought in succession of useful vegetation. Studies have revealed that protected silvi-pasture cover is best in erosion control than agricultural crops.
The importance of pasture/silvipastoral systems in improving the fertility status especially organic carbon and potassium of degraded soils has been demonstrated. With 20 years of cultivation under silvipastoral/pasture systems, the soil organic carbon under grasses improved from 0.47 to 0.58% in the surface layers and 0.23 to 0.28% in the lower layers, potassium from 470 to 616 kg ha-1 in the surface and 197 to 284 kg ha-1 in the subsurface layers. Mangalassery et al. (2014) reported that silvipastoral systems sequestered 36.3 to 60.0% more total soil organic carbon stock compared to the tree system and 27.1 to 70.8% more in comparison to the pasture system. They reported that soil organic carbon and net carbon sequestered were greater in the silvipastoral system.
System # 4. Horti-Pastoral System for Arid Soil Management:
The system is more suitable and useful for arid soils spread across India where average annual rainfall is less than 300 mm. The grasses like Cenchrus setigerus and Cenchrus ciliaris can be introduced between two rows of arid fruit tree for managing soils as the grasses act as vegetative barrier to control soil loss and to add some organic material to improve soil fertility status of these soils which are poor in fertility. Some legumes like Stylosanthes spp, Clitoria ternatia and wild groundnut are also grown with arid fruit plants.
These legumes fix environmental nitrogen into soil and improve overall fertility status of arid soils. Moreover, this system provides nutritious food and fodder for people and animal. In arid region, production of arable crops is not only inefficient but also highly unstable. Some prominent horti-pastoral system for arid zones are: ber + grasses/legume, pomegranate + grasses/legume and aonla + grasses/legume.
A demonstration of intercropping of stylo (Stylosanthes sp) with mango orchard in the farmer field in 2011 at Bhuj, Gujarat using a strip of 5 rows of stylo intercropped between rows of mango, produced stylo green fodder of 5100 t ha-1 with a dry fodder of 2800 kg ha -1. Another field demonstration was conducted on intercropping of clitoria and stylo with established orchard (mango) conducted on 3 farmers’ field in Bhuj in 2012. Five rows of legumes were intercropped with mango plantation planted at 6 m row spacing. A dry fodder yield 2.5 and 3.20 t ha-1 of clitoria and stylo, respectively, was produced, without any effect on mango plantation.
System # 5. Agri-Horti Systems:
Agri-horti system encompasses a combination of agriculture and horticulture enterprises together for the best utilization of land and other resources. This land management system aims at production of both agricultural crops and fruits. This practice can be adopted till 5-6 years or till canopy of trees becomes fully closed.
If the fruit trees are widely spaced, agriculture crops can be simultaneously grown. The practice is highly beneficial in fruit trees like ber which require pruning. Trials, conducted at CAZRI Regional Research Station, Kukma, Gujarat to develop viable agri-horti models suitable for the arid region, indicated that arid legumes such as cluster bean, cowpea and moth bean can be successfully intercropped with arid fruit crops such as aonla, ber and pomegranate without adverse impact on growth and yield of fruit crops.
Among the different land use systems, the maximum plant height and number of pods per plant of cluster bean, cowpea and moth bean under plantation of ber were observed and were higher than that under pomegranate and aonla. Such practices are beneficial for improving productivity/unit area and profitability of farmers apart from contributing to increased soil quality.