Effect of nitrogen management on grain yield of rice grown in a high-yielding environment under flooded and non-flooded conditions

Abstract

With increased cost and scarcity of irrigation water, flooded rice growing system may need to be replaced with water-saving technologies which includes part or complete removal of flooding and to be replaced with non-flooded aerobic conditions. However, to maintain high grain yield equivalent to that achieved with flooded rice, nitrogen (N) management may need to be modified. Experiments were conducted in a high-yielding environment with total N applied up to 180 ​kg ​ha⁻¹ and three application times to determine its effect on N uptake, grain yield and grain protein content of rice grown under aerobic (AR), delayed permanent water (DPW) and flooded (FD) conditions. Grain yield increased by 3.50–4.50 ​t ha⁻¹ with total N application rate of 180 ​kg ​ha⁻¹ in AR and 120 ​kg ​ha⁻¹ in both DPW and FD. Maximum yield was about 10.5, 12.0 and 13.0 ​t ​ha⁻¹ in AR, DPW and FD, respectively, and the difference was mostly reflected in the grain yield difference obtained under 0 N application. Apparent recovery of fertilised N and agronomic N use efficiency were similar between AR and FD, but DPW took up a higher proportion of N fertiliser applied before commencement of flooding and had slightly higher grain yield response to total N application up to 120 ​kg ​ha⁻¹. It is concluded that the limitation for grain yield for rice grown in the AR condition was the crop's inability to take up N from the soil, rather than the inability to take up N fertiliser or to convert the N uptake to grain yield.