الفهرس 
Introduction
Hazardous effects of nitrate and oxalate in leafyOnly 14 pages are availabe for public view
 |  | from | 64 |  |  |
| | | from | 64 | | |
Abstract
Two pot experiments were conducted under the green house of Fac. of Agric., Mansoura Univ. during two successive winter seasons of 2006-2007 and 2007-2008 to assess the substitution of some organic extracts instead of a part of mineral fertilizers for spinach, parsley and rocket vegetables. For each type of leafy vegetables used in this investigation, 20 treatments were arranged in randomized complete block design with three replicates which were the simple possible combination between five treatments of mineral fertilization as soil application at the rates of 0, 25, 50, 75 and 100 % from the recommended doses for leafy vegetables, i.e. 200 Kg ammonium sulphate, 150 Kg calcium super-phosphate and 100 Kg potassium sulphate. And four treatments of plant compost extract [tap water, fruit leaves, tomato foliage and potato foliage extracts] as foliar spraying. Thus, the total number of pots for each plant used was 60 pots. The obtained results could be summarized as follows: 5.1. Plant growth parameters: Foliar spraying of plant residues extracts, i.e. fruit, potato or tomato leaves as a single form significantly increased the average values of all growth parameters of plant for the three crops studied than those obtained for the untreated one. In this respect; spraying of potato leaves extract was superior for increasing the values of all growth parameters over the untreated. The average values of plant growth parameters in expression of plant height, cm, number of leaves per plant and fresh & dry yield g plant-1 of spinach, parsley and rocket crops at marketing stage during both seasons of the experiment were significantly increased as the rate of NPK mineral fertilization was increased from 25 % up to 75% from the recommended doses for these crops as compared to the control treatment. Increasing the rate of NPK fertilizers from 75 to 100 % significantly decreased the mean values of these parameters for the three crops under study. The same trend was realized in the second season. At any rate of NPK fertilizers under investigation, foliar application of plant extracts significantly increased the average values of all growth parameters for the three crops studied than those obtained for the plant received NPK only. The highest values were recorded for the plants received 75 % of NPK fertilizers combined with the foliar application of potato leaves extract. This trend was true for the three crops under study during both seasons of 2006-2007 and 2007-2008.5.2. Chemical composition: Foliar spraying of F, T or P extracts as solely spraying significantly increased the average values of N, P and K % and N-uptake by spinach, parsley and rocket plants over the untreated plant. Foliar spraying of potato residues extract was more effective than tomato or fruit leaves extracts for the three crops during both seasons. Soil addition of N, P and K fertilizers at the rates of 0, 25, 50 and 75 % from the recommended doses for these crops significantly increased the average values of N, P and K % and its uptake as the rate of NPK was increased. Foliar application of plant residues extracts, e.g., F, T or P coupled with 25, 50 and 75 % levels of N, P and K fertilization significantly increased the mean values of N and K % and its uptake, mg plant-1 by spinach, parsley and rocket plants over the untreated treatment in the two seasons of 2006-2007 and 2007-2008. While P% in spinach, parsley and rocket plants were not significantly affected during both seasons of the experimentation. On the contrary of this trend; P-uptake by spinach, parsley and rocket plants reported significant effect due to the interaction between soil addition of NPK rates and foliar spraying of plant residues extracts. In this connect at any level of NPK fertilization foliar, spraying of F,T or P extracts increased the average values of P-uptake by the three plants studied than these obtained for the plants treated with NPK rate only. More addition for NPK fertilizers at the rate of 100 % RD in the presence of plant residues extracts spraying had no significant effect between the mean values of N% and N-uptake mg plant-1 by the three crops studied as compared to the same values for the treatment of 75 %RD.5.3. Nitrate and nitrite accumulation: NO3-N and NO2-N contents were significantly increased due to spraying any of residues plant extracts as compared to the untreated plants. The highest values were realized for the plants sprayed with T extract while, the lowest one was recorded for the untreated plant. Such effect was happened during the 2nd season of the experiment. Soil addition of NPK fertilizers at the rates of 25, 50, 75 and 100 % from the recommended doses for these leafy vegetables sharply and significantly increased nitrate and nitrite contents over the untreated plants. The same trend of NO3-N was realized for NO2-N during both seasons of the experiment for the three crops under study. Spraying any of residues plant extracts on spinach, parsley and rocket plants with NPK fertilization highly decreased the average values of NO3-N and NO2-N mg kg-1 than those obtained for the plants treated with the same rates of NPK only to be around the safe limit of nitrate; 250 mg kg-1 and less than the critical limit, 2000 mg kg-1 as recommended by World Health Organization (WHO). Highest decrease percentages were realized for the plants treated with 100% RD of NPK coupled with foliar addition of potato foliage extract less than the same values for the plants received 100 RD only. 5.4. Total and soluble oxalate: The oxalate content vary considerably between the three plants under investigation ,spinach plant is classified as very high oxalate content, more than 5 g 100g-1 ; parsley plant is listed as high oxalate content, 3-5 g 100g-1, while rocket plant is considered as low oxalate content, less than 1 g 100g-1, on dry weight basis. Foliar spraying of plant residues extracts, F, T or P, in solely form had no significant effect on the average values of total oxalate, while it significantly increased the mean values of soluble oxalate as compared to the untreated plants. The highest values of soluble oxalate for spinach, parsley and rocket plant were recorded for the plants received T extract as foliar addition ,while the lowest one were realized for the untreated plants. Soil addition of NPK fertilizers at any rate of this study significantly increased the average values of total and soluble oxalate, g 100g-1, on dry weight basis in spinach, parsley and rocket crops during both seasons of the experiment as compared to the control treatment. There is no significant differences between the average values of total oxalate, g 100g-1DW, in spinach, and rocket plants due to an addition of NPK fertilizers at the studied rates coupled with spraying of F, T or P extracts comparing with the same values obtained for the plants received NPK rates only during both seasons of the experiment. An adversely effects were happened for the average values of total oxalate in parsley plant which significantly decreased for the plants treated with F, T or P in foliar way combined with NPK rates than those received NPK rates only. Foliar application of F, T or P extracts on spinach, parsley and rocket plants in the presence of NPK rates significantly decreased the average values of soluble oxalate, g 100g-1DW, for the three plants than those obtained for the plants treated with NPK rates only. The lowest values of soluble oxalate were realized for the plants received 25 % from RD of NPK and foliar with P extract in the two seasons of the experiment. 5.5. Iron content mg 100g-1: The highest content of iron mg 100g-1 was found in parsley plant, following by spinach plant and the lowest values were recorded for rocket plant. Foliar spraying of plant residues extract in single form significantly increased the average values of iron mg 100g-1 for the three studied plants. The mean values of iron mg 100g-1 for spinach, parsley and rocket plants tended to increases as the level of NPK fertilizers were increased as compared to the control treatment during both seasons of the experiment. Foliar application of F, T or P extracts on spinach, parsley and rocket plants grown under the levels of 25 , 50, 75 and 100% RD from NPK fertilizers significantly increased the average values of iron mg 100g-1 than those obtained for the plants received the same NPK rates only. Such effect was happened during both seasons of 2006-2007 and 2007-2008. from the results mentioned previously it could be concluded that: Solely addition of plant residues extracts under study gave a simulative effect on all parameters under investigation and the best one was obtained from the plants treated with potato foliage extract. In spite of the promotive effect for NPK mineral fertilization tell the rate of 75% from the recommended dose on the investigated parameters; increasing the rate of N, P and K fertilization to 100 % from RD had a depressive effect for these parameters for the three crops. At any rate of N, P and K fertilization studied, foliar spraying of plant residues extracts led to increase the average values of all parameters than those obtained for the plants treated with these rates of N, P and K fertilizers in single form. Using of 75% from the recommended doses of N, P and K coupled with spraying of potato residues extract was superior for increasing the average values of all parameters. Thus; under the same condition of this investigation it could be recommended that; foliar application of plant residues extracts either in a single form for organic farming or in combination with 75% from the recommended doses of N, P and K fertilizers for leafy vegetables is beneficial for production the best of high quality and safe yield of spinach, parsley and rocket vegetable crops.