Effect of Different Levels of Organic and Chemical Fertilizers on Yield, Harvest Index and Extract Percentage of Hemp (Cannabis sativa L.)

Introduction : Hemp is a dioecious and annual plant. The most important use to this plant is in the food, drug, and natural fibers. Proper fertilizer management for a medicinal plant species is important for increasing its yield and maintaining the quality of active principles. Sustainable farming is on the basis of natural fertilizer application with the aim of decreasing chemical fertilizers. Various studies show that application of animal manure with chemical fertilizers (as N, P and …) have positive effects on soil structure, microbial population, soil fertility, growth and yield of plant with the aim of protecting the environment. Therefore, the present study was under taken to evaluate the effect of organic amendments enriched with chemical fertilizers of nitrogen and phosphorus on yield and extract of hemp.
To study the effect of different levels of animal manure and chemical fertilizers, a split factorial experiment, based on complete randomized blocks design with three replications was conducted at the research Farm of Faculty of agriculture, University of Birjand, during the growing season 2014-2015. Experimental factors were animal manure (0, 10, 20 and 30 t. ha-1well rotted farmyard manure) as the main plot, and factorial application of three levels of N (0, 50 and 100 kg N ha-1 as Urea) with two levels of P (0 and 80 kg P2O5 ha-1 as triple and P was superphosphate) as sub-plot. Animal manure, P and half of the N fertilizer were applied before planting and the other half of N were applied by top dressing. Hemp were planted 5 may on rows 60 cm apart, with 30 cm distance between each hemp on row, at the depth of 3-4 cm. Measured traits included leaf, stem and seed weights, stem height and diameter, 1000 seed weight, and leaves extract percentage per square meter in sub-plot for female plants of hemp. Also percentage of female plants calculated per sub-plot. Finally, all variables were analyzed by SAS software (V. 9.1). Comparison of the averages attributes was performed using FLSD test at the 0.05 level of significant.
The results showed that the percentage of female plants did not affected by animal manure and chemical fertilizers. Stem height and diameter, leaf and stem weights and extract percentage were increased with increasing rate of animal manure, nitrogen and phosphate fertilizers. Phosphorus application caused a 11.2% increase in thousand grains weight. The highest stem and leaf yields were 2541.8 and 7001.6 kg ha-1 respectively, which were obtained by using 20 t. ha-1 animal manure with 100 kg N 80 kg P ha-1. An increased stem yield was also obtained by applying 30 t ha-1 animal manure with 50 kg N 80 kg P ha-1. Integrated using of 20 t. ha-1 animal manure with 100 kg N 80 kg P ha-1, and 30 t. ha-1 animal manure with 50 kg N 80 kg P ha-1 were appeared as the favorable fertilizing treatments for hemp.
It is suggested that combined usage of the animal manure and chemical fertilizers have more positive effects on growth and yield of hemp in compare with the use of fertilizers or animal manure lonely. Also hemp nutrition should be done according to the aim of producing.