Response of winter wheat to the application rate of raw and digested sheep manure alone and supplemented with urea in Libyan desert soil

Abstract

Applying digestate as fertilizer may reveal a different effect on crops compared with raw material. In this study, a pot experiment was conducted to evaluate the cultivation of winter wheat in the pristine desert soil through application of raw (RM) and digested sheep manure (DM) alone or supplemented with urea (RM + U and DM + U). Six application rates corresponding to 50, 150, 250, 350, 450 and 550 kg Tot N ha−1 were used together with unfertilized soil as a control. After sowing, germinated seeds were recorded at 4, 5, 6, 7, 10, 14 and 20 days from which the germination attributes calculated as time to reach 50% of germination (T50%), germinability (G), mean germination time (MT), and germination index (GI). Growth characteristics were measured as deficiency symptoms, plant height, plant tillering percentage, leaf area, ears length, biomass yields of ears, straw, root, total biomass, grain yield, a weight of 50 seeds, percent of P and protein in the grain. From the results, DM and DM + U gave better germination when compared to RM and RM + U. At high application rate, all fertilizers delayed germination which resulted in high values of T50% and MT, and low values of GI. Deficiency symptoms were seen (i.e. small leafs, short plants, brown spots and yellow stripes) at low application rate (50 kg Tot N ha−1) mainly in the DM and DM + U treatments. Most growth characteristics increased when increasing application rates, particularly in RM treatments. The combination with urea improved most growth characteristics but reduced root biomass and P percent in the grain. Raw manure alone revealed better results when compared to digested manure, even when combined with urea. Results suggested that a high application rate of raw and digested sheep manure alone or in mixture with urea is necessary for the soil to obtain high grain yield in good quality.