Abstract:

[Objective] This study was conducted to assess the effects of different nitrogen fertilizer application rates, planting densities, cutting periods and their interactions on the forage grass yield and nutritional quality of barley in Hetao region. [Method] Using barley variety ′Mengpimai No.5′ as research material, different levels of nitrogen fertilizer application rate [urea （N: 46%） as nitrogen fertilizer, pure nitrogen fertilizer application rates of 82.5 kg/hm² （A1）, 108.0 kg/hm² （A2）, 135.0 kg/hm² （A3）], planting density [3.75 million plants/hm² （B1）, 4.50 million plants/hm² （B2）, 5.25 million plants/hm² （B3）] as well as cutting period [heading stage （C1）, filling stage （C2）, milk maturity stage （C3）] were set up. The effects of the three factors and their interactions on forage grass yield and nutritional quality of ′Mengpimai No.5′ were analyzed. [Result] The nitrogen fertilizer application rate and cutting period had extremely significant （P<0.01） impacts on the plant height, fresh yield, hay yield, fresh to hay ratio as well as the contents of crude protein, acidic detergent fiber, neutral detergent fiber, calcium of ′Mengpimai No.5′, while planting density had limited impact on the forage grass yield. Nitrogen fertilizer application rate was the main factor affecting the fresh yield, crude protein content and neutral detergent fiber content, with contribution rates of 57.60%, 55.90% and 34.34% to the above three indicators, respectively. Cutting period was the main factor affecting the hay yield and acidic detergent fiber content, with contribution rates of 66.47% and 76.69% to the above two indicators, respectively. Under different nitrogen fertilizer application rates, the fresh yield, hay yield as well as the contents of crude protein, neutral detergent fiber, calcium, phosphorus of ′Mengpimai No.5′ were extremely significantly （P<0.01） different. Under different planting densities, the contents of neutral detergent fiber and calcium varied extremely significantly （P<0.01）. Under different cutting periods, there were extremely significant （P<0.01） differences in the plant height, fresh yield, hay yield, fresh to hay ratio as well as the contents of crude protein, acidic detergent fiber, neutral detergent fiber, calcium. [Conclusion] Nitrogen fertilizer application rate and cutting period are the crucial factors affecting the forage grass yield and nutritional quality of ′Mengpimai No.5′. Taking into account both forage grass yield and nutritional quality, the best performance is achieved with the nitrogen fertilizer application rate at 108.0 kg/hm², the planting density at 4.50 million plants/hm², and cutting at the milk maturity stage.

Key words: nitrogen fertilizer, cutting period, ′Mengpimai No.5′, quality