Effect of site preparation techniques on Prosopis juliflora in an alkali soil

Effects of three methods of site preparation, i.e. trench (30 cm deep and 30 cm wide dug across the plots), pit (30 cm × 30 cm × 30 cm) and augerhole (15cm diameter and 90 cm deep) on raising Prosopis juliflora plantations on a highly alkali soil (pH₂ 10.3) were studied in a field experiment at Gudha Experimental Farm of the Central Soil Salinity Research Institute, Karnal. A uniform dose of gypsum of 3 kg per plant was mixed with the excavated soil before trenches/pits/augerholes were refilled and Prosopis planted. The study indicated that mean plant height and girth growth, recorded at 2 year intervals from planting up to 8 years, were greatest with the augerhole method. Similarly, the air dried shoot and root biomass accumulated by Prosopis in 6 years was maximum in augerhole planting. In trench and pit planting, most of the roots were confined to surface layers (0–60 cm), whereas in augerhole the roots were able to pierce the hard CaCO₃ layer (caliche bed) and were nearly 2.5 m deep 2 years after planting. Differential site preparation techniques showed little effect on N, P, K, Ca, Mg, S and Na concentrations in plant parts (leaf, branch and stem) of Prosopis both at 2 and 6 years after planting. Total removal of N, P, K, Ca, Mg and S through Prosopis parts at 2 and 6 years after planting was maximum in auger planting and minimum in trench planting. The augerhole was also superior to other techniques in pod production, litter yield and nutrient additions to the site. However, litter quality remained unaffected owing to planting techniques. In general, there was marked decrease in pH and electrical conductivity and appreciable improvement in organic carbon and available N status of the experimental soil owing to Prosopis growth, but effect of different site preparation methods was not significant. This study showed that site preparation for planting Prosopis in high pH soils in the vertically downward direction is more important than reclamation of surface soil in the horizontal direction.