Effects of mowing regimes and climate variability on hay production of Leymus chinensis (Trin.) Tzvelev grassland in northern China

Leymus chinensis (Trin.) Tzvelev grassland is the most widely distributed native steppe vegetation type suitable for haymaking in the semiarid pastoral regions of north-east Asia. The long-term effects of four mowing regimes (mowing once a year, twice a year, once every 2 years and twice every 3 years), and climatic variability on the hay production from L. chinensis grassland were investigated using permanent plots over 27 years. The results showed that (i) the overall cumulative annual herbage production over the 27 years was the highest under ‘mowing once a year’, and ‘mowing twice a year’ did not produce any significant change in the amount of harvested herbage; (ii) mowing induced a reduction in herbage production mostly in the first couple of years, and the reduction was larger under frequent than less frequent mowing. The annual herbage production in harvest years was higher under less frequent mowing (once every 2 years, or twice every 3 years) than that under annual mowing, but the higher herbage production in harvest years under less frequent mowing could not compensate for the herbage not made into hay in the years without harvest; (iii) annual herbage production generally increased with annual precipitation, but the response of annual herbage production to precipitation was best described by quadratic (instead of linear or logarithmic) equations, which suggested a decline in annual herbage production under the highest annual precipitation in the region, and the relationships stood under different mowing regimes; and (iv) an analysis of hay yield and quality, and costs of the mowing operation, showed that the haymaking from L. chinensis grassland was financially viable as long as the herbage production was not extremely low under drought. It is concluded that the best practice for haymaking from L. chinensis grassland should be based on the rule of ‘mowing once a year’ in high-production years and grazing in low-production years; and a light grazing early in the season may increase hay quality mowed in the autumn if the grassland grows well early in the season in high-production years.