Changes in the competition for water between poplar and cotton in a
shelterbelt-farmland system caused by drip irrigation in oasis
Abstract
Farmland shelterbelt plays a crucial role in protecting arable land but
also exhibits high water consumption in arid areas. The coexistence of
shelterbelt and farmlands always lead to the competition for water.
However, the wide application of drip irrigation in recent years make
shelterbelt difficult to get water, leading to a more complex
relationships between shelterbelt and farmland in water use. Therefore,
the evapotranspiration (ET) of poplar shelterbelt and cotton field under
the drip irrigation were quantitatively analyzed, to explore the
relationship between shelterbelt and cotton under drip irrigation in
water use and determine the area and intensity of potential competition.
The results showed that due to the larger planting area and higher
density of cotton, the ET of cotton field was 56% - 66% higher than
that of poplar shelterbelt, especially in the seedling stage and
flowering and bolling stage. In the boll-opening stage of cotton, the ET
of poplar shelterbelt exceeded that of cotton field by 24.15%, and the
ET of cotton per unit area was significantly lower than that of poplar
shelterbelt. Besides, in the area with a distance of 0.1 - 0.5 times
tree height (H) from the shelterbelt (0.1H - 0.5H), shelterbelt had an
obvious competitive advantage because the root length density and
biomass were significantly higher than those of cotton in the 20-40 cm
soil layer, and the competition for water between them was the most
intense in this area. In >1H area, there was no poplar root
and no competition. Therefore, the introduction of a poplar shelterbelt
did not increase water consumption in the local area and aggravate the
water shortage in oases. However, the amount of irrigation to cotton
field close to the shelterbelt should be appropriately increased, to
reduce the loss of water caused by the consumption of poplar trees.