Performance of winter cereals grown on field-stored soil moisture only

According to climate change projections, winter cereal production will likely be exposed to increasing air temperatures and prolonged summer droughts. During the 2009/10 and 2010/11 growing seasons at Braunschweig, Germany, four cultivars each of barley (Hordeum vulgare L.), rye (Secale cereale L.), triticale (Triticosecale Wittmack), and wheat (Triticum aestivum L.) were grown in a mobile rain-out shelter with a nearby irrigated control to determine the maximal impact of water shortage on phenology, physiology, and yield. The rain-out shelter plots were subjected to severe drought stress by withholding rain during tillering to harvest. Permanent prevention of water supply caused an average 2 day earlier heading and flowering and a 19 day earlier loss of green leaves. Midday thermal images revealed consistently higher canopy temperatures under drought stress than under well-watered conditions. The drought related temperature increase was 3.7 K across crops and years. Contrary to canopy temperature, the spectral moisture stress index and the normalized difference water index did not clearly separate the dry from the wet environment. The drought-induced yield loss averaged 5.9 t ha-1 (63%) for grain dry matter and 9.2 t ha-1 (51%) for above-ground dry matter. Among the four cereal species, rye produced the highest grain and above-ground dry matter under both dry and wet conditions, and also had the coolest canopy. Based on the results of the present study, it is expected that rye will cope best, and barley second-best with the drier conditions of the changing climate.