Improving nitrogen‐use efficiency by using ridge tillage in rice paddy soils. (25th November 2020) - Qin, Chuan
Abstract: Nitrogen (N) fertilizers are increasingly being used to meet crop demand for the expanding human population. However, historical N‐use efficiency (NUE) is low for rice paddy fields compared to upland ecosystems. This study aimed to investigate the fate of N fertilizer and compared NUE under different tillage regimes in a rice‐based agroecosystem. A long‐term field study of tillage regimes (i.e. flooded paddy field, conventional tillage and ridge tillage) and 15 N isotope tracer methods (in situ and incubation) was used to determine N fertilizer fate and uptake. Nitrogen uptake by rice (which represents NUE) significantly differed between tillage regimes ( p < .05). Nitrogen‐use efficiency was 31% of applied N fertilizer for ridge tillage, which was the highest among the three tillage regimes, while the lowest NUE occurred for conventional tillage (17%). The soil residual N for ridge tillage was significantly higher (21%), than for the flooded paddy field or conventional tillage. The total gaseous N loss was highest for ridge tillage (28%) and lowest for conventional tillage (17%). Ammonia (NH3 ) volatilization accounted for the largest proportion of gaseous loss from N fertilizer for all three tillage regimes. However, the largest loss of applied N was with water (runoff and leaching), where N loss accounted for 20% of applied N for ridge tillage but up to 54% for conventional tillage. Ridge tillage changed the soil micro‐topography and water regimes leading to better N conservation. Based on these results, adoption of ridge tillage should significantly improve NUE for rice paddy fields.