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Two field experiments during two consecutive seasons, were conducted on corn (Zea mays L. var. Ghota-82), grown on a saline soil under flood irrigation system at ACSAD research station located at the Euphrates Valley, Deir-Ez-zor District, east of Syria. The objective was to study the effect of applying different ratios of mixed NO 3 -N and NH 4 -N fertilizers on the biomass yield of corn. Five rates of nitrogen (N) (0, 50, 100, 150, and 200 kg N/ha) were applied either in a single or in combination of two forms of 15 N labelled nitrogen fertilizers ( 15 NH4) 2 SO 4 and Ca ( 15 NO 3 ) 2 Total N, 15 N, nitrogen use efficiency (N recovery), and dry matter yield were the parameters investigated. The results showed that (1) the high concentrations of NH 4 -N reduced dry matter yield; (2) NO 3 -N was more effective in increasing total N 2373

A field experiment was carried out to study the effect of different rates of potassium (K) fertilizer [0, 50, 100, and 150 potassium oxide (K 2 O) ha -1 ] in the presence of increased supply of nitrogen (N) (120, 180, and 240 kg N ha -1 ) on cotton (Gossypium hirsutum L.) yield and the N and K use efficiencies using the 15 N isotopic dilution technique. Potassium fertilizer increased cotton yield, which was significant and more pronounced with the application of N in the high level (N3). The greatest cotton yield (6442 kg ha -1 ) was obtained in N2K3 treatment with an increase of 14% over the control. In addition, K fertilizer significantly increased N uptake efficiency in the N2 and N3 treatments. The greatest N uptake efficiency (98%) was in N2K3 treatment. The greatest K uptake efficiency (42%) was occurred in N3K1 treatment. In conclusion, the use of K fertilizer could be useful when growing cotton in soils of moderate to high N content to improve N uptake efficiency and consequently increase cotton yield.

Nutritive value of Sesbania aculeata hay was determined by estimating the nutritive components, nitrogen forms, in vitro digestible organic matter (IVDOM), and metabolisable energy (ME). A study was carried out to evaluate the effect of feeding 2 groups of Syrian Awassi ewes with 2 wheat straw-concentrate diets without (control) or with (experimental) added S. aculeata hay on some reproductive parameters of the ewes at different stages. Half of the wheat straw in the daily ration of the experimental group of ewes was replaced by S. aculeata hay (whole plant) grown on salty soil and irrigated by saline water. Daily metabolisable energy and crude protein consumed by the ewes in the 2 groups were the same during the different stages (2.5 months before mating, throughout pregnancy, and during lactation). Crude fibre and cell wall constituents’ values were lower, whereas the values of crude protein and crude ash were higher in leaves and pods than in stalks. The values of IVDOM in S. aculeata hay were 537, 380, and 626 g/kg DM, and of ME were 7.19, 5.43, and 8.58 MJ/kg DM for the whole plant, stalks, and leaves and pods, respectively. The values of buffer soluble nitrogen were 27% or 39% and of buffer soluble non-protein nitrogen were 21% or 35% of the total nitrogen in leaves and pods or stalks, respectively. Feeding with S. aculeata hay had no effects on the liveweight of the ewes during the periods before mating and throughout pregnancy, on mating rate, fertility rate, duration of pregnancy, birth weight, or weaning weight of lambs. Furthermore, feeding with sesbania hay had no effect on either the response of ewes to the oestrous synchronisation programme or on the blood serum concentration and pattern of progesterone during the period extending from the commencement of feeding the ewes sesbania hay (2.5 months before mating) until the time of their lambing.