Hw. Cutforth et Bg. Mcconkey, STUBBLE HEIGHT EFFECTS ON MICROCLIMATE, YIELD AND WATER-USE EFFICIENCY OF SPRING WHEAT GROWN IN A SEMIARID CLIMATE ON THE CANADIAN PRAIRIES, Canadian Journal of Plant Science, 77(3), 1997, pp. 359-366
In the semiarid region of the western Canadian prairies, seeding direc
tly into standing cereal stubble is gaining popularity. This four year
study was conducted at Swift Current, SK, to determine how seeding in
to tall (>30 cm high), short (about 15 cm high) and cultivated cereal
stubble altered the microclimate thereby affecting the growth and yiel
d of hard red spring wheat (Triticum aestivum L.). The treatments were
deployed immediately before seeding on plots that had overwintered wi
th tall stubble. Seeding wheat into tall stubble increased grain yield
and water use efficiency by about 12% compared to wheat seeded into c
ultivated stubble. Yield and water use efficiency for wheat seeded int
o short stubble were intermediate to the other stubble treatments. As
well, wheat seeded into tall stubble grew taller than wheat seeded int
o the cultivated stubble. Further, there was a tendency for spring whe
at grown in tall stubble to produce more dry matter and more leaf area
, to have a lower proportion of dry matter as leaves and a higher prop
ortion as stems, and to have a lower harvest index than the other trea
tments. Growing season evapotranspiration (ET) was not Effected by stu
bble height. When the seedlings were small, compared to cultivated stu
bble, tall stubble altered the microclimate near the soil surface by r
educing the daily average windspeed, soil temperature, and incoming so
lar radiation, and increasing the reflected solar radiation. Throughou
t much of the growing season, potential ET at the soil surface, measur
ed with minilysimeters, was significantly lower in the tall stubble. T
all stubble, compared to cultivated stubble, increased the proportion
of ET that was transpired by the wheat. As well, reduced windspeeds an
d increased photosynthetic area may have increased the efficiency of n
et carbon assimilation. To increase grain yields, producers in the sem
iarid prairies who direct-seed spring wheat are advised to seed into s
tubble left sanding as tall as practical (at least 30 cm).