REGINA – On a windy June day, when the sun’s intensity becomes oppressive, humans seek a tall grove of trees for welcome shade and shelter.
But what is a fragile seedling to do?
A study at the Agriculture Canada Swift Current research centre shows that in the brown soil zone, seeding into standing stubble from the previous year’s crop protects the young plant and allows it to make the best use of moisture.
“I think we all knew stubble is important but how much is the effect? And in particular, especially in the brown soil zone, is this whole debate between high disturbance versus low disturbance direct seeding – how important is it to … not disturb the standing stubble,” said Brian McConkey, a researcher from the centre.
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McConkey is part of a team that studied the effects of standing stubble on wheat, field peas, lentils and chickpeas. He reported findings to the Saskatchewan Soil Conservation Association direct seeding meeting here Feb. 12.
The four crops were seeded into three environments. The cultivated field was worked with a tandem disc followed with a harrow-packer, leaving about 50 percent of the stubble on the surface. The short stubble was mowed to a uniform height of about 15 centimetres (six inches) and the tall stubble was untouched, ranging from 24 cm to 42 cm. The wheat trial ran from 1992 to 1996 and the rest were tested in 1996 and 1997.
“In the early growth stage of spring wheat we are getting a phenomenal reduction of 70 percent in wind speed,” at a level 15 cm above the ground, he said.
The stubble also resulted in cooler soil temperature and reduced water loss from plants. In wheat, even as it grew taller than the stubble, the beneficial effect was still noticeable.
Plants growing in the tall stubble were taller with a five cm difference between cultivated and tall stubble plots in spring wheat.
In peas and lentils, tall stubble also caused the pods to be higher off the ground, making them easier to combine.
“To get another inch on your lowest pod should be worth an awful lot,” McConkey said.
Higher yields
In terms of yield, results increased in wheat and lentils as the stubble got higher. Compared to cultivated stubble, the spring wheat yielded six percent higher in short stubble and 12 percent higher in tall stubble.
Lentils yielded 12 percent more in short stubble and 21 percent more in tall.
The results were related to less evaporation, which allowed the stomates to remain open longer. Also the plants had more leaf area, increasing photosynthesis.
In field peas there was a nine percent yield improvement between stubble and cultivated, but no additional increase with taller stubble.
The chickpeas showed lower yields in tall stubble, probably because the tall straw gave too much shade to the low-growing crop.
McConkey said the effects of tall stubble are most beneficial in the dry brown soil zone.
In wetter areas, the tall stubble would boost humidity and increase the incidence of leaf and stem disease.
