MSc.

The study entitled “Leaf litter recycling in homestead agroforestry systems” was conducted during the period 2015-‘17 at College of Agriculture, Vellayani. The main objectives of the study were to hasten the decomposition process of leaf litter of two selected multipurpose tree species commonly grown in homestead agro forestry systems using microorganisms and earthworms, to enrich the litter compost with bio fertilizers, to assess the response of amaranthus to the enriched litter compost application and to monitor the changes in soil chemical and biological properties with use of the compost as nutrient source.
The study was conducted as two experiments i) composting of leaf litter and ii) assessing the response of amaranthus to enriched leaf litter compost. The experiment on composting of leaf litter was laid out in Completely Randomised Design with two factors replicated thrice. The treatments were two tree species (T1- Jack ; T2- Coconut) and eight composting methods [C1 - Composting inoculum (CoA, Vellayani) – powder formulation @ 20 g kg-1; C2 - Composting inoculum of Bacillus subtilis (CoH, Vellanikkara) - liquid formulation @ 1000 ml m-3, C3 - Earthworms (Eudrillus eugineae) @ 50 nos. m-3; C4 - Co-composting with poultry manure @ 10% w/w; C5 -C1 + C 3; C6 -C 2 + C3; C7 – Natural decomposition with soil; C8 - Natural decomposition without soil. Litter samples of the two tree species were collected during March, 2016 and analysed for bio-chemical constituents. Composting was done in cement pots of uniform size as per the treatments envisaged.

Analysis of the initial litter revealed higher nitrogen, lignin and phenol contents in coconut litter. Phosphorus and potassium contents were higher and C:N ratio wider in jack litter. Results of the decomposition study revealed that composting of leaf litter with different organisms and co-composting could significantly reduce the time taken for complete decomposition in both litter species. Co- composting was found to be the best method for hastening the decomposition. Decomposition was completed in 105 days in jack and 121 days in coconut litter, compared to the 206 and 238 days taken for natural decomposition in jack and coconut, respectively. The final composts of both litter had significantly higher amounts of nutrients and lower C: N ratio compared to the initial litter.
Based on the time taken for decomposition, nutrient contents and C: N ratio of the final composts, the three best composts in jack selected for the field experiment - i) C4 (N -1.87%, P- 0.73%, K- 0.16%, C: N ratio- 16.63:1, decay time -105 days), ii) C5 (N -1.35%, P-0.80% , K-0.25%, C:N ratio- 21.60:1, decay time-138 days) and iii) C2 (N- 1.30 %, P -0.64% , K- 0.20%, C:N ratio- 27.89:1, decay time- 165 days).
In the case of coconut leaf litter, the composts selected were - composting with i) C4 (N- 2.48%, P- 0.44% , K- 0.20 %, C : N ratio- 11.94:1, decay time – 121 days), ii) C6 (N- 2.18 %, P - 0.27% , K- 0.12%, C: N ratio- 13.70:1, decay time- 148 days ) and iii) C1 (N- 2.31 %, P -0.61 % , K- 0.14%, C: N ratio -16.48:1, decay time -179 days).
Field evaluation of the litter composts was conducted in the Instructional Farm, College of Agriculture, Vellayani during November 2016- February, 2017. The selected composts enriched with PGPR Mix I (@10 g kg-1 + rock phosphate @15% w/w basis and thermo chemically digested composts (Suchitha) of both species were used as nutrient source for amaranthus (var. Arun) at 50% substitution of recommended dose of nitrogen (KAU, 2016). The eight (T1-T8) treatments, along with a control (100% chemical fertilizer application, T9) were laid out in Randomised Block Design with three replications.

Application of coconut leaf litter composted with composting inoculum (liquid) + earthworm (T6) resulted in significantly taller plants at the different stages of growth. Leaf area index was highest in T6 and was on par with T4 and T2 at 60 DAT. Yield was significantly higher in T6 (20.20 t ha-1) and remained at par with T2 (17.96 t ha-1). Available K status of soil was significantly high in the treatments which received thermo chemically digested composts. Soil microbial count recorded higher values in T6 for bacteria (67.8 x 106cfu g-1 soil) and fungi (24.7 x 104 cfu g-1 soil). Actinomycetes was the highest (15.7 x 105 cfu g-1 soil) in T5.

Application of coconut leaf litter compost [composting inoculum (liquid) + earthworms] as nitrogen source resulted in higher net returns (₹ 144874 ha-1) and benefit cost ratio (1.92) in amaranthus.
The results of the study revealed that composting leaf litter with microorganisms and earthworms reduced the time for decomposition by up to 50 percentage. Co-composting with poultry manure was the best method for rapid composting in jack and coconut leaf litter. Through the process of enrichment, the nutrient content of the leaf litter compost found to be increased. Substituting 50 per cent recommended dose of nitrogen in amaranthus with coconut leaf litter compost (composting inoculum (liquid) + earthworms] resulted in significantly higher yield (46.7 per cent) and economic returns compared to 100 per cent chemical fertilizer application. The available nutrient status and microbial population in the soil were found increased through leaf litter compost application.