Effect of Organic and Chemical Fertilizers on effective traits on the Percentage of Light Absorption and Extract of Hemp (Cannabis sativa L.) in Birjand

Availability of nutrients needed by plants and ambient light are important in the growth and synthesis of active substance of medicinal plants. Various nutritional combinations have been assessed to study their effect on improving field management and production of medicinal plants. Nitrogen is often a limiting nutrient in plant growth in most agricultural soils. Nitrogen is a major component of chlorophyll, proteins, nucleic acid, vitamins and other organic compounds by which plants use sunlight energy to produce sugars from water and carbon dioxide (i.e., photosynthesis). It is also a major component of amino acids, the building units of proteins. Phosphorus is another element which has an important role in nearly every plant process that involves energy transfer. High-energy phosphate, contained in the chemical structures of adenosine diphosphate (ADP) and ATP, is the source of energy that drives the variety of chemical reactions within the plant. Nitrogen and phosphorus can be supplied through fertilizers or animal manure. Various studies show that combined use of manure and chemical fertilizers (as N, P and …) have positive effects on soil fertility and growth of plant as well as protecting the environment. Studies also show the effect of adequate nutrients on plant growth parameters, light absorption and biosynthesis in medicinal plants. Therefore, the present study was conducted to evaluate the effect of organic amendments enriched with chemical fertilizers (nitrogen and phosphorus) on effective traits in light absorption and alcoholic extract of hemp in two consecutive years in Birjand. 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 2013- 2014 growing seasons. Experimental factors include application of animal manure (well-rotted farmyard manure) at a rate of 0, 10, 20 and 30 ton ha-1 to the main plot. The sub plots were received nitrogen at rate of 0, 50 or 100 kg ha-1 (nitrogen in form of Urea) and phosphorus at rate of 0 or 80 kg ha-1 (P2O5 as triple superphosphate). Measured traits were shoot height and diameter, leaf area and leaf number, nitrogen percentage of leaf, canopy light absorption, shoot and leaf dry weights, percentage of extract of leaves and seeds. Nitrogen content of plants was determined by Kjeldahl method and light Absorption was measured by Sun scan. The data were statistically analyzed by SAS software (V. 9.1). Comparison of the means was performed using FLSD test at the 0.05 level of significant. The results showed that canopy light absorption highly correlated with the leaf numbers (0.676**), shoot height (0.621**), nitrogen percentage of leaf (0.543**) and shoot diameter (0.481**) respectively. Application of 30 ton ha-1 of animal manure resulted in less efficiency in increasing shoot height and diameter, leaf area and number and nitrogen percentage of leaf. The absorption of light by plant was higher in treatments with higher nitrogen content in leaf. The study showed that weight of shoot and leaf following treatment increased by animal manure, nitrogen and phosphorus supplements, which subsequently increased final weight of extract from leaves and seeds.
Application of 30 ton ha-1 of animal manure and 100 kg ha-1 of nitrogen resulted in 20.1% and 20.2% increase in content of leaf extract respectively, while application of 100 kg ha-1 of nitrogen resulted in 20% increase in total weight of extracts from seeds. Seed extracts were also highly correlated with the dry weight of leaves. Therefore, the study suggests that adequate nutritional supplement to soil can increase plant growth and final weight of the leaf and seed extracts from plants. Most seed extract estimated in combined treatment of 30 ton ha-1 animal manure and 80 kg ha-1 of phosphorus. The rate of plant growth was lower in the first year compare to the second year, which can be due to higher salinity of soil and animal manure and temperature of germination in the first year.
Overall, the findings of this study showed that application of 30 ton ha-1 of animal manure can provide the plants with adequate level of nitrogen and phosphorus resulting in increased level of extracts of leaf and seed in hemp plant and can reduce the need for nitrogen and phosphorus fertilizers use