INTRODUCTION:

Soil properties under different trees play a vital role in assessment of soil health. The various soil properties viz. physical, chemical and biological properties are greatly affected by the tree litter fall as considerable amount of nutrients are returned through it and become available to the plants. Leaf litter fall of the trees brings about important changes in physical, chemical and biological characteristics of soil and balances the nutrient reserve of soils. Ultimately these processes result in availability of nutrients which control the soil fertility and also increase productivity of the crops (Yadav and Meena, 2009; Sharma and Chaudhary, 2007).

In arid and semi-arid regions both macro and micronutrients are available in limited quantity in soil and fertilizers are also unavailable to farmers due to cost or other reasons. Therefore, improvement of such soil can make a substantial contribution to crop production. Secondly the organic matter content in these soils is also low. Originating mainly from litter fall in trees, soil organic matter, besides its importance for soil fertility, is the feeding resource for soil fauna and essential for soil functioning (Lavelle and Spain 2001). The litter produced by trees has different amount and different composition based on the structure and the species diversity of the plant which compiles it. Therefore, it is critical to understand the amount and pattern of litterfall in the trees (Wang et al., 2008). Considering the importance of trees in soil and other benefits for sustaining crop production, the present study was conducted to quantify the changes in soil fertility and contribution of leaf litter fall to different soil organic carbon pools.

MATERIALS AND METHODS:

The study was conducted at Balsamand Research Farm which is located about 27 km away from CCS Haryana Agricultural University Hisar. The experimental area has an arid climate with mean annual rainfall of 220 mm, 80 percent of which is received in July to September and has an undulating topography characterized by high wind velocity and sand dune. The minimum and maximum temperatures are 1.0°C and 45.5°C in the month of January and June receptively. Litter fall was collected at monthly intervals from different plantations i.e. shelterbelt, Azadirachta indica, Ailanthus excels and Prosopis cineraria. For the collection of litter 20 replicates of 1×1m wooden frames (10 cm in height) were placed inside the plantation. Litters from each plantation were oven dried at 60°C, until a constant weight was reached before taking the final reading. The soil samples from 0-15 cm soil depth from 3 distances (2, 5 and 10 m) and different plantations along with control (devoid of trees). The samples were air-dried and ground to pass through a 2 mm sieve. The samples were analyzed for soil organic carbon, dissolved organic carbon, microbial biomass carbon, available macro (N, P and K) and micronutrients (Zn, Fe, Mn and Cu). The available N in the soil samples was determined by alkaline potassium permanganate method (Subbiah and Asija, 1956), available P and K were determined following standard procedures (Jackson, 1973). Available micronutrients were extracted with DTPA extractant (Lindsay and Norvell 1978) and estimated on an atomic absorption spectrophotometer. Organic carbon was determined by Walkley and Black (1934) method, dissolved organic carbon by dichromate and oxidation method (Ciavitta et al., 1989) and microbial biomass carbon was determined by chloroform fumigation method (Vance et al., 1987).

Statistical Analysis:

The data of available soil nutrient and different organic pools were subjected to statistical analysis using ANOVA technique in randomized block with four replications. Mean separation was done with the critical difference (CD) test at 5% level of significance (Panse and Sukhatme 1985).

Figure 1. Leaf literfall under different plantation during study period

RESULTS AND DISCUSSION:

Leaf litter fall:

Litter fall (included leaves, branches, barks, flowers and pods) collected in different plantations during different months are shown in figure 1. The total litterfall during the study period under different tree plantations ranged between 1712 and 4126kg/ha Litter fall under different plantations was found maximum in the month of January and it was minimum in February. Annual litterfall showed considerable variation among different plantations. Litter accumulation under the different plantations canopy was highest in the shelterbelt followed by Prosopis cineraria and lowest in the Azadirachta indica. The pattern of annual litter production by different plantations was in the order of: shelterbelt > Prosopis cineraria >Ailanthus excelsa >Azadirachta indica. The variations in the litterfall production among the plantation were due to differential litter production capacity for different tree species and its growth habits (Das and Das 2010). Overall it was observed that the pattern of litterfall from each plantation exhibited a similar pattern and the highest production of litterfall (88.9%) was recorded from December to February in the different plantations. Among different tree plantation the contribution of litterfall 38, 25, 21 and 16% for shelterbelt, Prosopis cineraria, Ailanthus excels and Azadirachta indica, respectively. This may be due to water or temperature stress which activates the synthesis of abscissic acid in the foliage. The quantity and pattern of litter production varies with tree species, growth pattern, age, density and canopy characteristics and also the environmental conditions like temperature, water and mineral nutrient availability which limit litter production. These results are in accordance with the findings of Cleveland et al. (2004) who reported that climatic conditions and rainfall directly influence the litter production dynamics.

Table 1. Effect of different plantations and distances on available N (kg/ha) of soil

Plantation	Distance from tree (m)			Mean
	2	5	10
Shelterbelt	116.9	101.2	79.9	99.3
Azadirachta indica	95.4	83.6	58.6	79.2
Ailanthus excelsa	99.3	87.6	66.3	84.4
Prosopis cineraia	110.5	99.1	74.5	94.7
Mean	105.5	92.9	69.8
Control (devoid of trees) 55.9
CD at 5%	Plantation (P): 4.1 Distance (D): 3.5 P × D : NS

Table 2. Effect of different plantations and distances on available P (kg/ha) of soil

Plantation	Distance from tree (m)			Mean
	2	5	10
Shelterbelt	13.6	11.6	11.1	12.1
Azadirachta indica	10.1	9.9	8.9	9.6
Ailanthus excelsa	10.9	10.1	9.5	10.2
Prosopis cineraia	12.8	12.1	10.2	11.7
Mean	11.9	10.9	9.9
Control (devoid of trees) 9.6
CD at 5%	Plantation (P): 0.6 Distance (D): 0.5 P × D : NS

Table 3. Effect of different plantations and distances on available K (kg/ha) of soil

Plantation	Distance from tree (m)			Mean
	2	5	10
Shelterbelt	248.3	223.4	204.5	225.7
Azadirachta indica	218.3	199.6	187.6	201.8
Ailanthus excelsa	221.3	216.3	191.4	209.7
Prosopis cineraia	240.2	223.1	202.9	221.9
Mean	232.0	215.6	196.6
Control (devoid of trees) 188.9
CD at 5%	Plantation (P): 1.6 Distance (D): 1.4 P × D : NS

Available macronutrients:

The effect litter fall on soil available macronutrients is shown in tables 1 to 3. The perusal of data showed that availability of nutrients (N, P and K) was maximum under shelterbelt plantations in all the distances and it was minimum under control. Maximum availability of nutrients was recorded at 2m distance whereas; it was minimum at 10m distance from the tree. This trend was similar in all the plantations. The available nutrients (N, P and K) under all the plantations and distances differed significantly to each other. However, their interactive effect was found non-significant. Available macronutrients (N, P and K) content decreased significantly with increase in distance from tree. Available N content under tree species was higher than the nearby site without trees (control) among different plantations. Amongst the various tree species, the N content was the highest under shelter belt (116.9 kg/ha) and it was closely followed by Prosopis cineraria (110.5 kg/ha) and the lowest concentration was found under Azadirachta indica. (95.4 kg/ha). Similar pattern of available P and K was also followed under these trees and the respective values were 13.6; 12.8 and 10.1; 248.3; 240.2 and 218.3 kg/ha. The improvement in available N under trees was more at 2m and 5m than 10m distance in different plantations. The available P and K also followed the similar trend under different treatment combinations with respect to distance. The higher content of available nutrients (N, P and K) on under tree species is attributed to accumulation and decomposition of litterfall on the soil surface. It leads to mineralization of organic N and P from the litter and its release into the soil. In case of P, the organic acids released through decomposition of litterfall reduce metal ions through chelation in soil and they compete for exchange sites, thus, releasing P from soil. Higher availability of K at surface layers under trees is attributed to liberation of K from decomposition of litterfall as well as solubilization of insoluble forms of K present in soil due to organic decomposition products. The differences in available N content under different tree species might be due to variation in total litter production, nutrient concentration of litter and varying rates of mineralization in these species. Pandey et al. (2000) compared the influence of trees on soil organic, total and mineral N and P content with the area without trees in central India and found that these soil parameters were greater under trees compared to canopy gap indicating the influence of trees on soil nutrient status.

Table 4. Effect of different plantations and distances on DTPA extractable Zn (mg/kg) of soil

Plantation	Distance from tree (m)			Mean
	2	5	10
Shelterbelt	3.51	3.48	2.12	3.04
Azadirachta indica	2.68	2.25	1.68	2.20
Ailanthus excelsa	2.91	2.52	1.79	2.41
Prosopis cineraia	3.19	3.10	1.91	2.73
Mean	3.10	2.80	1.90
Control (devoid of trees) 1.58
CD at 5%	Plantation (P): 0.04 Distance (D): 0.04 P × D : NS

DTPA-extractable micronutrients:

The DTPA extractable zinc, copper and manganese in soil were significantly influenced by different plantations and distances, but the interaction between them was found non-significant (Table 4). The maximum (3.1 mg/kg) significantly higher DTPA extractable-Zn was recorded in shelterbelt as compared to other plantations and sole cropping. The DTPA extractable-Zn decreased significantly with each successive increase in distance from tree and it was found minimum at 10m distance from different plantations. The higher amount of Zn at near the trees was due to higher accumulation of organic matter on surface soil. The trees extract nutrients from deeper soil layer and bring them to top soil layer through litter fall and fine root biomass. Plant cycling is considered as the leading factor, and anthropogenic disturbance and leaching were the secondary factors that affecting the vertical distributions and topsoil accumulation of nutrients under different land uses (Jobbage and Jackson, 2001).

Table 5. Effect of different plantations and distances on DTPA extractable Cu (mg/kg) of soil

Plantation	Distance from tree (m)			Mean
	2	5	10
Shelterbelt	2.61	1.75	1.28	1.88
Azadirachta indica	1.32	1.15	0.69	1.05
Ailanthus excelsa	1.72	1.32	0.94	1.33
Prosopis cineraia	2.31	1.51	1.05	1.62
Mean	1.99	1.43	0.99
Control (devoid of trees) 0.64
CD at 5%	Plantation (P): 0.02 Distance (D): 0.02 P × D : NS

Table 6. Effect of different plantations and distances on DTPA extractable Fe (mg/kg) of soil

Plantation	Distance from tree (m)			Mean
	2	5	10
Shelterbelt	7.05	5.51	3.89	5.48
Azadirachta indica	4.69	3.49	2.94	3.71
Ailanthus excelsa	5.10	3.91	3.31	4.11
Prosopis cineraia	5.72	4.75	3.61	4.69
Mean	5.60	4.40	3.40
Control (devoid of trees) 2.81
CD at 5%	Plantation (P): 0.05 Distance (D): 0.05 P × D : NS

Significantly highest DTPA extractable-Cu (2.61 mg/kg) was recorded under shelterbelt as compared to sole crop and other plantations at different distances (Table 5). Like other nutrients, the copper availability was also closely followed by Prosopis cineraria when compared with other tree species while comparing with shelterbelt. Campanha et al. (2007) reported higher Cu under agroforestry system than monoculture. Singh and Sharma (2007) reported increase in Cu under poplar-based agroforestry system with increase in age. The DTPA extractable-Cu in soil decreased significantly with each successive distance i.e. from 2m to 10m. The higher amount of Cu at 2m distance may due to higher accumulation of organic matter on soil near the tree. The DTPA extractable-Fe and Mn followed the similar pattern under different plantations and distances (Table 6 and 7). The maximum (7.05 and 10.36 mg/g) and significantly highest DTPA extractable- Fe and Mn were recorded under shelterbelt at 2m distances and it was closely followed by Prosopis cineraria as compared to other tree plantations. The availability of DTPA extractable-Fe and Mn in soil decreased significantly with each successive increase in distance from tree i.e. from 2m to 10m distance. Jiang et al. (2009) reported that the DTPA extractable-Mn decreased significantly with each successive increase in soil depth.

Table 7. Effect of different plantations and distances on DTPA extractable Mn (mg/kg) of soil

Plantation	Distance from tree (m)			Mean
	2	5	10
Shelterbelt	10.36	9.69	8.78	9.61
Azadirachta indica	7.94	6.21	5.75	6.63
Ailanthus excelsa	8.69	7.65	6.21	7.52
Prosopis cineraia	10.14	8.64	7.45	8.74
Mean	9.28	8.05	7.05
Control (devoid of trees) 5.31
CD at 5%	Plantation (P): 0.02 Distance (D): 0.02 P × D : NS

Table 8. Effect of different plantations and distances on organic carbon (%) of soil

Plantation	Distance from tree (m)			Mean
	2	5	10
Shelterbelt	0.36	0.23	0.18	0.26
Azadirachta indica	0.24	0.16	0.12	0.17
Ailanthus excelsa	0.29	0.17	0.15	0.20
Prosopis cineraia	0.31	0.22	0.18	0.24
Mean	0.30	0.20	0.16
Control (devoid of trees) 0.14
CD at 5%	Plantation (P): 0.02 Distance (D): 0.03 P × D : NS

Figure 2. Dissolved organic carbon under different plantation at different distances

Figure 3. Microbial biomass carbon under different plantation at different distances

Organic carbon pools:

The effect of litter fall on soil organic carbon is shown in table 8. Among the different plantations organic carbon content was highest near the tree i.e. 2m distance. As the distance from the trees was increased the organic carbon also decreased. This was due to less litter fall quantity away from the trees. Highest organic carbon was found under shelterbelt plantation and it was closely followed by Prosopis cineraria in all the distances. The organic carbon was lowest under control. Similar trend was also observed in case of dissolved organic carbon and microbial biomass carbon (Figures 2 and 3). These soil organic pools under different plantation and distances differed significantly to each other, but their interactive effect was found non-significant. The tree plantation showed more microbial biomass carbon, organic carbon and dissolved organic carbon than control means that the presence of tree species and the lesser removal of plant residues contribute significantly to mitigate the loss of carbon. Also, trees have higher potential to build up and sequester carbon in soils because of the increased rates of organic matter addition and retention (Lenka et al., 2012). The higher organic carbon pools under trees can be attributed to permanent input of plant residues that supply available C and maintain a high microbial biomass, conforming reports by Perez et al. (2004), Ndaw et al. (2009) and Araujo et al. (2010). According to them higher contents of different soil organic pools were found in areas under native vegetation compared to devoid of tree (control) areas.

CONCLUSION:

The block plantation of shelterbelt, Azadirachta indica, Ailanthus excels and Prosopis cineraria showed considerable variation of annual litter fall and litter accumulation was highest in the shelterbelt followed by Prosopis cineraria and lowest in the Azadirachta indica. The different tree plantations studied under the present investigation improved the availability of nutrients and organic carbon pools of the soils near the tree. The higher amount of N, P and K in soils under these tree species compared to field without plantation might be related to nutrient return through litter fall. The content of Fe, Mn, Zn and Cu was also improved greatly under these tree species than the field without plantation. The improvement in soil fertility may be due to litter fall from trees, which on decomposition enriched the soil organic matter and nutrient status of soil. Among the tree species, Prosopis cineraria contributed more in enhancement of soil fertility. The results from the study indicated that increase in soil organic carbon content and other available nutrients might be helpful in improving productivity potential of arid regions.

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Received on 14.07.2022 Modified on 28.08.2022

Research J. Science and Tech. 2022; 14(4):226-232.

DOI: 10.52711/2349-2988.2022.00037