Enhancements in yield, agronomic, and zinc recovery efficiencies of rice-wheat system through bioactive zinc coated urea application in Aridisols

BACKGROUND: Zinc (Zn) deficiency and source-dependent Zn fertilization to achieve optimum Zn levels in rice and wheat grains remain global concern for human nutrition, especially in developing countries. To-date, little is known about the effectiveness of bioactive Zn-coated urea (BAZU) to enhance the concentration, uptake, and recovery of Zn in relation to agronomic efficiency in paddy and wheat grains. RESULTS: Field experiments were carried out during 2020–21 on the rice-wheat system at Lahore, Faisalabad, Sahiwal, and Multan, Punjab, Pakistan using four treatments viz.T(1) (Urea 46% N @ 185 kg ha(-1) + zero Zn), T(2) (Urea 46% N @ 185 kg ha(-1) + ZnSO(4) 33% Zn @ 15 kg ha(-1)), T(3) (BAZU 42% N @ 103 kg ha(-1) + Urea 46% N @ 62 kg ha(-1) + 1% bioactive Zn @ 1.03 kg ha(-1)) and T(4) (BAZU 42% N @ 125 kg ha(-1) + Urea 46% N @ 62 kg ha(-1) + 1% bioactive Zn @ 1.25 kg ha(-1)) in quadruplicate under Randomized Complete Block Design. Paddy yield was increased by 13, 11, 12, and 11% whereas wheat grain yield was enhanced by 12, 11, 11, and 10% under T(4) at Multan, Faisalabad, Sahiwal, and Lahore, respectively, compared to T(1). Similarly, paddy Zn concentration was increased by 58, 67, 65 and 77% (32.4, 30.7, 31.1, and 34.1 mg kg(-1)) in rice whereas grain Zn concentration was increased by 90, 87, 96 and 97% (46.2, 43.9, 46.7 and 44.9 mg kg(-1)) in wheat by the application of BAZU (T(4)) at Multan, Faisalabad, Sahiwal, and Lahore, respectively, in comparison to T(1). Zinc recovery was about 9-fold and 11-fold higher in paddy and wheat grains, respectively, under BAZU (T(4)) treatment relative to T(2) while, the agronomic efficiency was enhanced up to 130% and 141% in rice and wheat respectively as compared to T(2). CONCLUSION: Thus, T(4) application at the rate of 125 kg ha(-1) could prove effective in enhancing the rice paddy and wheat grain yield along with their Zn biofortification (∼34 mg kg(-1) and ∼47 mg kg(-1), respectively) through increased agronomic and Zn recovery efficiencies, the underlying physiological and molecular mechanisms of which can be further explored in future.