INTEGRATED EFFECT OF MINERAL AND ORGANIC NITROGEN FERTILIZATION IN THE PRESENCE OF SOME NITRIFICATION INHIBITORS ON GROWTH, PRODUCTIVITY AND FRUIT QUALITY OF TOMATO

Two field experiments were conducted at Talkha region, Dakahlia Governorate, Egypt, during seasons of 2010 and 2011 to evaluate the integrated effect of mineral and organic nitrogen fertilization in the presence of some nitrification inhibitors, i.e., Dicyandiamide (DCD), 3, 4-dimethylpyrazole-phosphate (DMPP) and neem cake (NC) on growth, chemical composition, productively and fruit quality of tomato F1, GS-12.
The obtained results indicate that:
-    The combined addition of 120 kg mineral-N and 80 kg organic-N (5.12 ton compost / fed^-1) with DMPP induced significant increment in vegetative growth characters (plant height, foliage fresh weight and leaf area) and chemical composition (N, P and K uptake) of tomato plants. This treatment led to a significant increase in marketable yield of tomato fruits, whereas, the control treatment (mineral-N at 200 kg/ fed^-1 as the recommended application) showed the highest significant unmarketable tomato yield during both seasons of the study.
-    The highest accumulation of nitrate and nitrite contents in tomato fruits were obtained from addition of control treatment, however, the lowest values were obtained under either the addition of 120 kg mineral-N and 80 kg organic-N with DMPP or 80 kg mineral-N and 120 kg organic-N with DMPP.
-    Application of 120 kg mineral-N and 80 kg organic-N with DMPP produced the highest significant values of lycopene, total soluble sugars, vitamin C and TSS contents of tomato fruits, also recorded the highest net return and benefit-cost ratio.
It could be concluded that the combined addition of 120 kg mineral-N fertilizer (585.4 kg/ fed^-1 as ammonium sulphate) and 80 kg organic-N (5.12 ton/ fed^-1 from rice straw compost) with DMPP (4.8 kg/ fed^-1) in tomato fields is the favorable recommendation to increase the vegetative growth characteristics, chemical composition, yield and quality than the recommended mineral-N fertilizer (975.6 kg/ fed^-1 as ammonium sulphate). Such treatment will save about 40 % of the applied mineral-N fertilizer, giving the remarkable net return and benefit-cost to the farmers as well as minimizing the negative effects of the excessive use of mineral-N fertilizers on environment and human health.