Abstract:

In the high-cold desert area of China， forage production is limited by the traditional planting patterns used and by the low natural productivity of the landscape. The purpose of this study was to explore a promising irrigation regime to increase forage yield and achieve efficient use of water and soil resources. For a mixed-sowing of oats （Avena sativa） and vetch （Vicia sativa）， a field experiment was conducted to analyze the effects of seven patterns of regulated deficit irrigation on the soil moisture， soil temperature， and soil nutrient levels of the forage crop， as well as the plant height， stem-leaf ratio， yield， and water and nitrogen use efficiency of the mixed-species forage crop. The seven irrigation patterns were： mild water deficit at jointing stage （BW₁， soil moisture at 65%-75% of field capacity； SM% FC）， moderate water deficit at jointing stage （BW₂， 55%-65% SM% FC）， severe water deficit at jointing stage （BW₃， 45%-55% SM% FC）， mild water deficit at flowering stage （KW₁， 65%-75% SM% FC）， moderate water deficit at flowering stage （KW₂， 55%-65% SM% FC）， severe water deficit at flowering stage （KW₃， 45%-55% SM% FC）， and full irrigation during all crop growth stages （QW₀， 75%-85% SM% FC）. It was found that： 1） The average soil water storage decreased with the increasing water deficit. Under the same water deficit conditions， there was no significant difference between the average soil water storage at jointing stage and at flowering stage. 2） The average soil temperatures of water deficit treatments were significantly higher than those of the full irrigation treatment. At the same level of water deficit， the average soil temperature was significantly higher in treatments with water deficit at the jointing stage than those with water deficit at the flowering stage. 3） Compared with levels before sowing， the soil nutrient contents of all treatments were reduced after harvest. The treatment KW₁ significantly increased soil available nitrogen content， while moderate or severe water deficit inhibited the absorption of soil available phosphorus and potassium by the forage crops. 4） Under the same irrigation pattern， the plant height， stem-leaf ratio， and yield of oats were significantly higher than those of vetch. The water consumption of the seven irrigation regimes was 386.1-502.6 mm. Compared with the treatment QW₀， the treatment KW₂ reduced the irrigation amount by 20.6%， had a statistically equal forage yield， and achieved a higher water use efficiency （31.5 kg·ha^-1·mm^-1）， irrigation water use efficiency （81.0 kg·ha^-1·mm^-1）， nitrogen absorption efficiency （0.99 kg·kg^-1）， and partial productivity of nitrogen fertilizer （191.1 kg·kg^-1）. In conclusion， moderate water deficit during the flowering stage was a water-saving， yield-increasing， and highly efficient water management regime for the tested oat-vetch forage crop at this site in a high-cold desert area.

Key words: regulated deficit irrigation, mixed seeding, artificial grassland, soil environment, growth, high-cold desert area