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

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.

Thus, T4 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.

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.T1 (Urea 46% N @ 185 kg ha-1 + zero Zn), T2 (Urea 46% N @ 185 kg ha-1 + ZnSO4 33% Zn @ 15 kg ha-1), T3 (BAZU 42% N @ 103 kg ha-1 + Urea 46% N @ 62 kg ha-1 + 1% bioactive Zn @ 1.03 kg ha-1) and T4 (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 T4 at Multan, Faisalabad, Sahiwal, and Lahore, respectively, compared to T1. 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 (T4) at Multan, Faisalabad, Sahiwal, and Lahore, respectively, in comparison to T1. Zinc recovery was about 9-fold and 11-fold higher in paddy and wheat grains, respectively, under BAZU (T4) treatment relative to T2 while, the agronomic efficiency was enhanced up to 130% and 141% in rice and wheat respectively as compared to T2.