Can potato add to China's food self-sufficiency? The scope for increasing potato production in China

China is enhancing potato production in both area and quantity. While the potato area is large, the actual yields remain low. Besides, the water resources used for irrigation are increasingly under pressure in potato production areas. This study aimed to assess the scope for increasing potato production in China. The key climate zones in China were identified, for which the potential yield (Yp) and water limited yield (Yw) of potato (expressed in fresh matter (FM)) were estimated by two crop growth models over 10 years (2006-2015). The Yp and Yw and yield gaps (i.e., the difference between Yp and actual yield (Ya) under irrigated conditions (Yg-p) and between Yw and Ya under rainfed conditions (Yg-w)) were evaluated at local, provincial and national level, for potatoes under both irrigated and rainfed conditions. The water availability through rainfall, water productivity (WP) and the water input gaps to realize potential rather than water-limited potato yields were identified at provincial level. The Yp in the country was on average 50.1 ton FM ha(-1), and Yg-p as a percentage of Yp was 66%. At provincial level, the Yp varied from 38.8 ton FM ha(-1) in Sichuan in the southwest to 66.4 ton FM ha(-1) in Qinghai in the north. At national level, the Yw was 43.7 ton FM ha(-1) and Yg-w as a percentage of Yw was 61%. At provincial level, the Yw was lowest in Shaanxi (27.7 ton FM ha(-1)) and highest in Qinghai (57.9 ton FM ha(-1)). Water productivity for potential yield (WP-p) ranged between 30.7 and 54 kg dry matter (DM) mm(-1) ha(-1) in Shaanxi and Qinghai, respectively, and for actual yield (WP-a) between 7.9 kg DM mm(-1) ha(-1) (Shanxi) and 22.3 kg DM mm(-1) ha(-1) (Sichuan). Water supply through rainfall is close to sufficient for non-water limiting potato growth in the southwest. The water input gap in the north was highest in Shaanxi (i.e., 243 mm) and lowest in Heilongjiang (i.e., 39 mm). There is a large scope to improve potato yields at current rainfall levels, especially in Qinghai and Heilongjiang in the north and in Guizhou in the southwest. By closing the exploitable yield gap (i.e., difference between 80% of Yp - or of Yw - and Ya) for the current production area, potato could contribute to an additional 1.1 and 0.9 10(14) kcal, respectively, under irrigated and rainfed conditions. This is much more than that for rice (0.2 10(14) kcal extra energy due to yield gap closure) under irrigated conditions, and similar or more than for maize under irrigated (1.0 10(14) kcal) and rainfed (0.5 10(14) kcal) conditions. We conclude that compared with the cereal staple crops, potato has a larger potential to maintain domestic food security and self-sufficiency, and to enhance water use efficiency.