Grain yield, yield components and nitrogen economy of irrigated second-crop common Buckwheat (Fagopyrum esculentum Moench) in a cold-temperate region

Abstract

Common buckwheat (Fagopyrum esculentum Moench) is a species with great nutritional value and promising to be cultivated as a second crop in irrigated fields of cold-temperate regions with short growing seasons. However, little information exists regarding the nitrogen (N) economy of common buckwheat as a second crop following a high-yielding winter cereal. This study aimed to quantify grain yield, its components, and the grain protein content, and to evaluate N economy processes such as the initial N use efficiency (INUE), the N uptake efficiency (NUptE), the N internal efficiency (NIE) for biomass and grain yield and the N harvest index (NHI) among different treatments of N availability at sowing in four site-year experiments of common buckwheat as a second crop in irrigated fields of the southwestern Pampas of Argentina. The variety Mancan, used in this study, lasted between 73 and 92 days (888–1073 °C days) from sowing to harvest. Grain yield was highly correlated with achene number but not with achene weight. Grain yield ranged from 405 to 2725 kg ha-1, with an interaction between treatments and experiments, with major differences among experiments and minor differences among N availability treatments. Relative N uptake was maximized at a higher value of N availability (160 kg N ha-1) than grain yield (50 kg N ha-1), associated with higher responses of N uptake, vegetative N uptake and grain protein content than grain yield to N availability. However, NUptE featured a negative response to N availability in all experiments. NHI was highly variable among experiments, ranged between 0.51 and 0.83 and was affected by N availability in only two experiments. NIE for biomass and grain yield were 80 kg kg-1 and 36 kg kg-1, respectively, which were lower than those of most cereals but higher than those of other non-cereal grain crops. A short crop cycle of the variety Mancan, an average grain yield of 1594 kg ha-1 among experiments in this study, a low N availability requirement to maximize grain yield and high values of NIE for biomass and for grain yield suggest that buckwheat is a promising species for second crop sowing in cold-temperate regions.