**4. Soil moisture conservation and water quality improvement by agroforestry practices**

Trees in the agroforestry system can increase the crop yield by conserving soil moisture through mulching. Soil moisture availability is higher under trees than open areas and the agroforestry system increases the infiltration characteristics of the soil and thus, it traps more water and increases the soil water content. In the arid region, Kumar et al. [31] observed the effect of soil water availability on *Hordeum vulgare* (barley) yield is compared for various agroforestry models with *Prosopis cineraria*, *Tecomella undulate*, *Acacia albida* and *Azadirachta indica*. It was found that *P. cineraria*, *T. undulate*, *A. albida* and *A. indica* increased crop yield by 86%, 48.8%, 57.9%, and 16.8% over the control. It is well proved that the agroforestry system improves the quality of the groundwater compare to the cropping system most of the applied nutrients are leached out which pollutes the groundwater [32]. Deep-rooted trees used in agroforestry consume the excess nutrients applied in the crop field. Therefore, acts as a filter and releases water with fewer nutrients and reduces groundwater pollution.

Seobi et al. [33] studied the effect of agroforestry and grass-legume buffers on soil hydraulic retention and soil physical properties for Putnam soil (fine, smectitic, mesic Vertic) in corn (*Zea mays*)–soybean (*Glycine max*) field in northeastern Missouri in USA from 1991 to 1997. Agroforestry buffers used for the experiment were 4.5 m wide and 36.5 m apart. The trees and grasses used in agroforestry buffers were redtop (*Agrostis gigantean*), brome (*Bromus spp*.), and birdsfoot trefoil (*Lotus corniculatus*) with pin oak (*Quercus palustris*, swamp white oak (*Q. bicolor*), and bur oak (*Q. macrocarpa*). Soil samples were collected from buffers and crop fields using core samplers up to 40 cm with a 10 cm interval. Pressure starting from 0 to −33 kPa was applied to soil samples and corresponding water content was noted. Results showed the grass and agroforestry buffers can store 0.9 cm and 1.1 cm more water for top 30 cm soil in comparison to the row crop. The reason for the increased soil water content in the agroforestry and grass buffer system may be attributed to the enhanced porosity. Thus, it increases the infiltration characteristics of the soil and reduces runoff.

The land is being cleared in arid and semi-arid regions of Australia to meet agricultural development by clearing the native forests. However, gradual salinization is being a problem of those lands due to rising groundwater level. In a study in two different experiment sites in Western Australia, the reclamation of those lands is carried out by using pinus (*Pinus radiate* & *P. pinaster*) - pasture and eucalyptus (*E. sargentii*, *E. wandoo, E. camaldulensis and E. calophylla*) -pasture agroforestry measures. Site 1 has an area of 76 ha out of which agroforestry covers 47 hectares whereas site 2 has an area of 30.25 ha out of which 17.24 ha covered with agroforestry. The long-term annual rainfall and pan evaporation for site 1 were recorded as 717 mm and 1800 mm respectively whereas for site 2, annual rainfall and pan evaporation was 713 mm and 1613 mm respectively. Results showed that groundwater level in site 1 was decreased by 1 m relative to the groundwater level in pasture land whereas in site 2 decreases in groundwater level were 2 m over the period 1979–1989. The salinity level is also found decreased by 9% and 6% for site 1 and site 2 respectively in comparison to the initial stage [34]. It is expected that due to less water availability caused by climate change will affect 2.7 to 4 billion people

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*Potential and Opportunities of Agroforestry Practices in Combating Land Degradation*

**5. Agroforestry promising for soil fertility replenishment**

worldwide by 2050 [35]. Climate change will affect the water quality in terms of sediment, nutrients, dissolved organic carbon, pathogens, pesticides, and salt content in water [36]. In this scenario of changing climate, agroforestry practices will act as a remedy and will enhance the micro-climate, reduce runoff and evaporation, and also increase the soil moisture content and groundwater level and thus agroforestry practice will increase the water availability and food security guarantee.

The role of the agroforestry system in enhancing and maintaining soil fertility and productivity and sustainability has been well documented [37]. Even those trees which do not fix N, enhance soil physical properties which helps in crop growth. Maintenance and enhancement of soil fertility levels are necessary for regional and global food security purposes. Several studies are reported and proved that from agroforestry system nutrient loss is less as compared to the agriculture farming. Grewal et al. [38] have reported that leucaena-napier grass allowed less nutrient loss compared to the traditional agricultural system. There was net gain of 38 kg N, 10 kg P, and 20 kg K as compared to the net loss of 15 kg N, 2 kg P and 14 kg K ha−1 in the traditional agricultural system. In a study with *Acacia nilotica* + *Saccharum munja* and *Acacia nilotica* + *Eulaliopsis binate* the soil organic carbon was found 0.91% and 0.99% after 5 years [39]. Tomar et al. [40] reported the effect of green manuring with different agroforestry tree species on dry matter yielding and production as well as post-harvest fertility of low land rice (*Oryza sativa*) in India. The green leaves of the tree species viz., *Erythrina indica*, *Acacia auriculiformis*, *Alnus nepalensis*, *Parkia roxburghii* and *Cassia siamea* at 10 t ha−1 were applied in rice fields during the rainy season of 2008 to 2010. The dry matter and paddy yield from those fields were compared with the fields which were treated with recommended N-P2O5-K2O (80:60:40 kg ha−1) and control (no fertilizer and manure). The soil of the field was sandy clay loam, acidic, low in P content (6.95 kg ha−1), medium in N (277 kg ha−1), high in K (258 kg ha−1), and OC (2.56%) respectively. In 1st and 2nd year of study, the grain and straw yield was higher in NPK plot (**Table 3**). However, in 3rd-year grain and straw yield was higher in green-leaf manure plots. *Erythrina* tree leaf manure was found superior among the other tree leaf manures. Application of green leaf manure increased the available soil NPK increased more compared to recommended N-P2O5-K2O dose and control. Therefore, based on the above observation, it could be said that plant residues can have long term implications in maintaining soil fertility without decreasing the crop yield. In arid and semi-arid regions, *Prosopis cineraria* in low intensity about 120 trees ha−1 increases the N level of soil. It is also used as a source of animal feed, fuel, timber and intercropping with millet and legumes increase the grain yield [41]. In an alley cropping system red alder (*Alnus rubra*) in maize experiment at Oregon in the USA, it was found that 32–58% of total N in maize was transferred from N fixed by red alder and more transfer obtained when the distance between red alder and maize is less [42]. Avasthe et al. [43] reported that large cardamom (*Amomum subulatum* Roxb.) based agroforestry practice was found effective in conserving soil, water, and nutrients in the fragile mountain ecosystem of Sikkim Himalayas in India in comparison to a mixed forest and traditional maize-soybeanmustard cropping sequence. In this agroforestry system, cardamom is grown under the shade tree *Alnus nepalensis* which fixes atmospheric N. OC, available N, K except P was found higher in the soil in cardamom based on agroforestry system compared to maize-soybean-mustard cropping sequence. On the other hand, soil loss and nutrient loss in the soil also found less in large cardamom based

*DOI: http://dx.doi.org/10.5772/intechopen.97843*

*Potential and Opportunities of Agroforestry Practices in Combating Land Degradation DOI: http://dx.doi.org/10.5772/intechopen.97843*

worldwide by 2050 [35]. Climate change will affect the water quality in terms of sediment, nutrients, dissolved organic carbon, pathogens, pesticides, and salt content in water [36]. In this scenario of changing climate, agroforestry practices will act as a remedy and will enhance the micro-climate, reduce runoff and evaporation, and also increase the soil moisture content and groundwater level and thus agroforestry practice will increase the water availability and food security guarantee.
