Background and Objectives
Management of organic fertilizers utilization is of the main components of organic crops production which can greatly affect the yield and quality of plants. Due to the short time course of leafy vegetables production, farmers commonly use nitrogenous chemical fertilizers for the nourishment of plants. The results are huge nitrate accumulation on the edible parts of the vegetables and hence the deteriorating health side effects. So, owing to the necessity of vegetables in the daily diet, resorting to the production methods to reduce the nitrate accumulation and even preserve and add up the nutritious quality of vegetables is of great interest.
Materials and Methods
This experiment was conducted to evaluate the effects of deferent levels of cow, vermicompost and poultry organic fertilizers (0, 10, 20 and 30% in volume) and urea (102, 204 and 306 g Kg/ha) on nitrate accumulation (morning and evening sampling time) and Fe2+, Zn2+ and potassium concentration and total phenolic content as well as on some growth characteristics of spinach as RBCD design with three replications in Azarbaijan Shahid Madani University during 2016.
The results revealed that the highest morning nitrate accumulation (2435 mg Kg-1 Fwt) and that of evening (2052 mg Kg-1 Fwt) belonged to 306 kg/ha urea treatment. Leaf length was effected by 20% (3.6 cm) and 30% (8.8 cm) of poultry manure. The highest data for TSS and root fresh and dry weight were attained by 10 and 20% of cow manure. The treatments, 20 and 30% of vermicompost, cow manure and 30% poultry manure increased the leaves fresh and dry weight. All levels of poultry and vermicompost manure had positive effects on potassium content. The highest amounts of Fe2+, Zn2+ and total phenolic content were recorded in 10, 20 and 30% cow manure and vermicompost manure
Nitrate accumulation in vegetables is dependent upon several intrinsic and extrinsic factors of which, mineral nutrition is of crucial importance. Considering the positive response of spinach to the application of organic fertilizers, it seems that using these organic fertilizers would greatly decline the chemical fertilizers input as well as reduces the environmental side effects of chemicals and virtually goes to the production of safe organic products under sustainable production systems.