This work was conducted on sweet potato cv. 93 to evaluate the effect of Ca (NO3)2 and (NH4)2 SO4 fertilizers as chemical N-sources in different rates either single or with biofertilizer (nitrobien) on the plant growth, yield and its components .
The obtained results could be summarized as follows:
Application of Ca (NO3)2 fertilizer significantly increased most studied characteristics of plant vegetative growth, non-marketable yield as compared with (NH4)2 SO4 fertilizer. In contrast, (NH4)2 SO4 fertilizer application was generally more useful than Ca (NO3)2 fertilizer for sweet potato production, it exerts, significant increases on total yield, marketable yield and plant yield (weight and number).
Inoculation of plants with biofertilizer (nitrobien) led to increase plant vegetative growth characteristics, tuber root yield and its components and beside that significantly reduced non-marketable yield comparing with the uninoculated ones.
Raising nitrogen fertilizer levels from 0 to 80 kg N/fed resulted in a significant increase in all studied characteristics of plant vegetative growth, total and marketable yield.
In general, the positive interactions between N.-sources and biofertilizer (nitrobien) have often been observed. Aplication of Ca (NO3)2 fertilizer with biofertilizer gave the highest values of plant vegetative growth, while the greatest values of tuber root yield and its components were obtained by using (NH4)2 SO4 fertilizer with biofertilizer.
The interaction between nitrogen fertilizer levels and biofertilizer had a significant effect on all studied characteristics of vegetative growth, with exception of number branches /plant. It also had a significant effect on total and marketable yield. Inoculation of sweet potato plants cv. A 93 and adding 60 kg N/fed in form of (NH4)2 SO4 achieved great yield were nearly indentical for those produced by 80 kg N/fed without biofertilizer.
Therefore, application of (NH4)2 SO4 fertlizer as a N-source at 60 kg N/fed to sweet potato plants cv A- 93 and inoculation of plants with biofertilizer (nitrobien) are the recommended treatments for raising productivity and improving quality of tuber roots.