Supplementary Biomass Addition Enhances the Crop Productivity: Evidence from a <i>Gliricidia sepium </i>- Based Alley Cropping Practices in Gazipur District of Bangladesh

Two consecutive experiments were conducted to investigate the effect of alley cropping practices on the productivity of cauliflower during the winter season of 2016-2017 and 2017-2018. An eleven-year-old <i>G. sepium</i>-established alley cropping field was used as the experimental site located in Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh. The experiments were done using a split-plot design. Three alley widths of <i>G. sepium</i> <i>viz</i>. W<sub>3.0</sub>, W<sub>4.5</sub>, and W<sub>6.0</sub> (3.0 m, 4.5 m, and 6.0 m) comprised factor A, the main plot factor. Within each main plot, five nitrogen (N) doses namely N<sub>0</sub>, N<sub>25</sub>, N<sub>50</sub>, N<sub>75</sub>, and N<sub>100</sub> contributed the five levels of factor B (sub-plot factor) each replicated thrice. Control plots received allied N doses without pruned biomass to facilitate comparison with the alley cropping. The data from the two seasons on cauliflower were subjected to pooled analysis using R-statistics. Results revealed that, growth and yield attributes of cauliflower thrived in all the alley cropping plots compared to control (absence of tree), and increased along with the increase in applied N. Further, we assessed what combinations of alley width and N level provide the highest yield and found that, W<sub>6.0</sub>×N<sub>100</sub> treatment combination yielded the highest cauliflower yield (33.55 t ha<sup>‒1</sup>) which was statistically equivalent to the yields of W<sub>6.0</sub>×N<sub>75</sub> and W<sub>6.0</sub>×N<sub>50</sub> combinations. It was also observed that all the alley cropped plots given higher economic benefit compared to control, specifically with the first three highest Benefit-to-Cost Ratios (BCRs) calculated in W<sub>6.0</sub>×N<sub>100</sub> (3.27), W<sub>6.0</sub>×N<sub>50</sub> (3.23), and in W<sub>6.0</sub>×N<sub>75</sub> (3.21) treatment combinations. The outcome suggests that using pruned materials can be a viable alternative to enhance crop productivity, profitability and reduce the reliance on nitrogenous fertilizer.