Effect of Leucaena mulch incorporation on soil properties under maize-wheat crop rotation

A field study was carried out for 3 years at Dehradun consisting of four levels of air-dried leucaena (Leucaena leucocephala L.) leaves mulch material viz.; no mulch (M₀), 2 (M₁), 4 (M₂), and 6 (M₃) t ha⁻¹ as main treatments and four timings of incorporation of the mulch as sub-treatments viz., 0 (immediately after harvest, T₁), 15 (T₂), 30 (T₃) and 45 (T₄) days after maize harvest. It was found that bulk density of the soil was reduced from 1.44 gm cm⁻³ (no mulch) to 1.40 gm cm⁻³ with leucaena mulch level of 6 t ha⁻¹. Days after incorporation of the mulch did not show marked effect on bulk density. It was noted that water stable aggregates (> 0.25mm) improved due to the use of leaves mulch, but the days after incorporation did manifest marginal improvement in the percentage of water stable aggregates (>0.25 mm). Available water content and other physical as well as chemical properties of soil improved with the use of leaves mulch. Minimum effect was observed when Maximum available water content (12.2 per cent) was observed at 45 days in comparison to incorporation immediately after harvest (11. 7 per cent) of the previous maize crop. Infiltration rate improved from 0.65 cm hr⁻¹ (no mulch) to 0.72 cm hr⁻¹ (6 t ha⁻¹). Soil organic carbon improved from 0.55 per cent under no mulch to 0.60, 0.68, 0.72 per cent, respectively with application of mulch @ 2, 4, 6 t ha⁻¹ levels of mulch, over no mulch (0.55 per cent) after the period of three years. Relative status of total nitrogen was of the order of 0.07 per cent with 6 t ha⁻¹ mulch as compared to 0.05 per cent nitrogen with no mulch. Available phosphorus indioated marginal increase from 29 ppm (no mulch) to 30.8 ppm. Available potash showed perceptible improvement (169 ppm) with 6 t ha⁻¹ level of mulch as against 160 ppm (with no mulch). Soil pH was considerably reduced from 6.8 (no mulch) to 6.4 (6 t ha⁻¹), whereas days after incorporation showed less reduction in soil pH.