Optimizing nutrient management of wheat in Tunisia

This project was initiated in 2014 in Tunisia to develop a Nutrient Expert® (NE) tool for Tunisian farmers and extension specialists to implement appropriate nutrient management practices for wheat production in rain-fed and irrigated areas. In the 2015/2016 cropping season, six omission nutrient trials were established in four regions of Tunisia: semi-arid rain-fed area of Manouba and Siliana, favorable rain-fed area of Beja, and irrigated area of Kairouan. Each experimental plot was planted with bread wheat (BW) and durum wheat (DW) under seven nutrient treatments: optimum treatment (OPT), nitrogen (N), phosphorus (P), and potassium (K) omission from OPT, SSNM (based on the recommendations of NE tool), control (without fertilizer application) and farmer fertilizer practice (FFP). The ranges of fertilizer applied (kg/ha) OPT treatment from semi-arid to irrigated areas were 10 to 182 kg N + 45 to 67 kg P₂O₅ + 25 kg K₂O. The ranges of fertilizer applied in SSNM treatment from semi-arid to irrigated areas were 111 to 134 kg N + 25 to 90 kg P₂O₅ + 20 to 50 kg K₂O.

For both types of wheat, the highest grain yields of 5.8 t/ha (DW) and 6.4 t/ha (BW) in favorable rain-fed, and 6.1 t/ha (DW) and 7.9 t/ha (BW) in the irrigated area were obtained in the SSNM treatment. In both areas, no significant effects of P and K on grain yields of DW and BW were observed, however N omission reduced the grain yield of DW by 9% and 12% in the favorable rain-fed and irrigated areas, respectively. Omission of N reduced BW grain yield by 12% in the irrigated areas, however, no significant effect of N was observed in BW in the favorable rain-fed areas. In the semi-arid areas, no significant difference of grain yield was observed between nutrient treatments for DW and BW in Manouba, and DW in Siliana. For BW in Siliana, omitting N, P and K reduced the grain yield by 14%, 20%, and 10%, respectively. The SSNM treatment increased the grain yield of BW significantly in all rain-fed areas compared to the FFP treatment, with no significant difference in the irrigated area. In the case of DW, SSNM increased the grain yield by 43% in the irrigated area of Kairouan, and by 28% in the semi-arid area of Manouba.