Development of poplar-based alley crop system for fodder production and soil improvements in semi-arid tropics

Scarcity of green fodder in semi-arid regions is a major bottleneck for the adoption of livestock-based production systems. To address this challenge with a focus on sustainable and appropriate land-use systems for forage production, this study compared forage species yield, tree growth and soil nutrients when sorghum (Sorghum bicolor), berseem (Trifolium alexandrinum L.) and cowpea (Vigna unguiculata) were intercropped with Populus deltoides arranged in six spacing geometries (3 x 3 m, 4 x 3 m, 5 x 3 m, 6 x 3 m, 7 x 3 m and 8 x 3 m). During the study, two cropping rotations sorghum-berseem (S-B crop rotation) and cowpea-berseem (C-B crop rotation) were followed. The yield of green fodder crops increased significantly as the spacing between the rows increased from 3 to 8 m. Tree density or planting geometry significantly affected plant height and diameter at breast height (DBH) with decline in plant height and increase in DBH with increase in tree density. Among all the treatments of poplar-based alley crop systems, the maximum green forage yield was recorded under the widest poplar spacing (8 x 3 m) for all three forage crops evaluated in the system. The overall yield reduction in the sorghum-berseem system ranged from 10 to 22 percent with increasing tree density and from 10 to 56 percent in the cowpea-berseem system compared to control. The soil organic carbon (%) and available N, P and K decreased exponentially with the increase in row to row distance of poplar trees. Greatest soil organic carbon and available N, P and K were measured under the closely spaced (3 x 3 m) trees managed with cowpea-berseem rotation. Land Equivalent Ratio (LER) of poplar-based system with S-B crop rotation under 8 x 3 m spacing was highest and this system was more profitable than P. deltoides + C-B crop rotation. The study showed P. deltoides with S-B crop rotation at 8 x 3 m spacing is most productive system.

Automated summary

The study found that planting Populus deltoides with sorghum, berseem, and cowpea in different row spacings had a significant impact on green forage yield and tree growth, with the best row spacing being 8 x 3 m. Tree density and planting geometry significantly affected plant height and diameter, with the highest green forage yield recorded under the widest row spacing of 8 x 3 m.