Effect of Nitrogen, shading and intercropping on alfalfa-ziziphus agroforestry system under arid land conditions

To assess the arid lands agroforestry potential, a field experiment was performed at the Agricultural Research Station of King Abdulaziz University, located at Hada Al-Sham during the 2013 and 2014 seasons. Alfalfa was evaluated in a Ziziphus agroforestry system at a distance of 1 m, 2 m and 4 m from the ziziphus tree and were supplied with three different levels of nitrogen fertilizer 0 kg/ha, 200 kg/ha and 400 kg/ha in the form of commercial Urea. The fertilizer were subdivided into split doses and applied as manual broadcasting after each cutting. A split-split plot design was used with three replications. Forage growth rate and biomass accumulation were measured at ten different intervals approximately at a period of 30-40 days. Forage was harvested in 10 different cuts and all this data consisting of plant height, fresh biomass accumulation and dry biomass accumulation and leaf nitrogen content were also measured. Statistical analysis described significant impact for intercropping, planting distance and nitrogen fertilizer on all studied traits. The maximum effect of urea fertilizer was documented for the highest dose of 400 kg/ha but it was statistically non-significant to 200 kg/ha. Distance of planting from the Ziziphus tree produced variable trend for all forages at different cut numbers but 2 m produced maximum plant height and biomass accumulation for most of the cut numbers. The interaction of 200 kg N/ha, intercropping and 2 m distance produced optimum forage growth and biomass accumulation as compared to the sole plantation under no fertilization. Â