Optimizing nutrient management of wheat in Tunisia


02 Jun 2018

2017 Annual Interpretive Summary

This project was initiated in 2014 in Tunisia with the objective to develop a Nutrient Expert® (NE) fertilizer decision support tool for Tunisian farmers and extension specialists to implement appropriate nutrient management practices for wheat production in the rain-fed areas. In the 2016-2017 cropping season, nine nutrient omission trials (three per region) were established in three regions of Tunisia: the semi-arid unfavorable region of Siliana, the semiarid favorable region of Manouba, and the subhumid region of Beja. Each experimental plot was planted with bread wheat (BW) and durum wheat (DW) under seven nutrient treatments: 1) optimum treatment (OPT); 2) omitting nitrogen (N) from OPT; 3) omitting phosphorus (P) from OPT; 4) omitting potassium (K) from OPT; 5) site-specific nutrient management (SSNM) based on the recommendations of the NE tool; 6) control (without fertilizer application); and 7) farmer fertilizer practice (FFP). The rates of fertilizer applied per hectare in the OPT treatment from semi-arid to the favorable rain-fed areas were 107-117 kg N/ha + 45 kg P2O5 + 25 kg K2O. The ranges of fertilizer applied in the SSNM treatment from semi-arid to favorable rain-fed areas were 80-96 kg N, 42-56 kg P2O5, and 24-41 kg K2O.

For both species of wheat and all the regions, the highest wheat yields were obtained in the SSNM treatment: 4.3 t/ha (DW) and 4.7 t/ha (BW) in the sub-humid favorable rain-fed (Beja) region; 4.4 t/ha (DW) and 4.1 t/ha (BW) in the semi-arid favourable area (Manouba); and 1.3 t/ha (DW) and 2 t/ha (BW) in the semiarid unfavorable area (Siliana). Contrasting results were observed in terms of nutrient effects on the grain yield in the different regions. In water-limited Siliana, there was no significant effect of N, P, and K on grain yield for both DW and BW. In Manouba, omitting N, P, or K reduced the grain yield of DW by 50, 27, and 28% respectively, however no significant effect was observed on the grain yield of BW. In Siliana, omitting N, P, and K had no significant effect on the grain yield for both species of wheat. Compared to FFP treatment, the SSNM treatment significantly increased the grain yield of BW in all the rain-fed areas. In the case of DW, SSNM significantly increased the grain yield by more than 43% over FFP only in the Manouba region.