Effects of Chemical and Organic Fertilizers on Growth, Yield and Yield Component of Tomato (Lycopersicon sculentum L.)

Although using animal manures and crop residues as a traditional method for increasing soil fertility and crop yield has a long history but Conventional agricultural systems rely on the use of chemical fertilizer due to its immediate availability of nutrients. In many of modern agricultural systems using chemical fertilizers as a fast and easiest way to reduce nutrient deficiency and increasing soil fertility is considered. Intensive and continuous use of chemical fertilizers leads to decreasing the stability and sustainability of agricultural systems and also poses major threat to environment and human health. Organic fertilizers have positive effects on physiochemical and biological attributes of soil and could be classified in three different groups (i.e. Animal manures, green manure and composts).Using animal manure not only increase soil fertility but also could result in increasing infiltration, aeration and water holding capacity of soil. The main role of these fertilizers is related to physical change in soil. Different types of composts such as municipal waste compost and vermicompost also have similar positive effects, but usually the farmers observe the main effect of these organic fertilizers in long term. In order to investigate the effects of different types of organic fertilizers on growth indexes, yield and yield component of tomato (Lycopersicon sculentum L.) current experiment was conducted.
The experiment was conducted based on randomized complete block design (RCBD) with three replications and six treatments in the research station of Shahid Beheshti University. The experimental treatments were: Control or no fertilizer (NF), chemical fertilizer (CF), cow manure (CM), poultry manure (PM), vermicompost (VC) and municipal waste compost (MC). Considering nitrogen concentration in all of the treatments different amounts of these fertilizers were used based on nitrogen recommendation for the field, so in all of the treatments the total amount of applied nitrogen was equal (ca. 150 kg ha-1). Tomato seedlings were transplanted in experimental plots when the height of seedling reached to 15-20 cm. Total amount of tomato yield calculated at the end of growing season after four harvests. At the end of growing season by using five plants from each plot the dry weight of shoot, plant height, number of lateral branches and the number of fruits measured. Analysis of variance was performed using SAS and mean comparisons done by Duncan’s multiple range test (P ≤ 0.05).
Based on results effects of experimental treatments on shoot dry matter, plant height, number of lateral branches, number of flowers and fruits per plant and leaf area index (LAI) was significant. Using all type of fertilizers comparing to control treatment resulted in increase shoot dry matter and the highest amount of shoot dry matter observed in VM and CF treatments. Different treatments have significant effect on plant height and highest amount of this trait observed in PM treatment. There was no significant difference between CM and control treatment for plant height and number of lateral branches but the highest number of lateral branches observed in MC treatment. The highest LAI (6.2) observed in VC and CF whereas the lowest LAI (3.3) was in control treatment. Effect of treatments on total yield also was significant and highest amounts of yield observed in CF (22.9 ton ha-1) and VC (20.8 ton ha-1) but the lowest was in control treatment (7.5 ton ha-1). Treatment effect on all of yield component except mean weight of fruit was significant and by using CF and VC the number of flower per plant comparing to control treatment increased 143 and 129 percent respectively.
Although in this experiment the highest amount of crop yield obtained in CF treatment, but by replacement of chemical fertilizer with vermicompost tomato yield decreased just about 10%, so it seems that by considering the environmental issues, using vermicompost instead of chemical fertilizer is justified. In all of the organic treatments tomato fruit yield significantly was higher than control treatment so it could be concluded that organic fertilizers directly through nutritional effects and indirectly by amending soil physical and chemical properties could increase the yield of tomato.