Chemical and physical changes in standing cereal straw residues in no-till fallow and its relationship to nitrogen and phosphorus availability
Adjustments to nitrogen and phosphorus fertilization rates may be required in fields which receive a no-till (herbicide) fallow treatment as compared to the conventional tillage fallow. For example, there is potentially greater immobilization of nutrient in no-till fields.
IPNI-1993-CAN-SK11
30 Aug 2001
Justification
- In drier regions of the Great Plains such as southern Saskatchewan, Alberta, and parts of Montana and North Dakota, cereal - fallow rotations continue to dominate, mainly because of the need for a fallow period to shore sufficient moisture to produce economic yield and lower the risk of crop loss. However, in an effort to better conserve moisture and the soil resource, and as a result of lower costs for the herbicide glyphosate, producers are shifting from mechanical tillage to herbicides (no-till) to control weeds over the fallow period. This has led to questions about the impact of this shift on fertilizer requirements, particularly by producers, who want to optimize fertility in their new management program. The goal of the proposed research is to shed some light on this aspect.
Adjustments to nitrogen and phosphorus fertilization rates may be required in fields which receive a no-till (herbicide) fallow treatment as compared to the conventional tillage fallow. For example, there is potentially greater immobilization of nutrient in no-till fields as the standing straw is finally worked into the soil at or near the time of seeding as compared to conventionally tilled fields where the straw is gradually worked into the soil over the previous year's fallow period. Furthermore, the impact on nutrient availability which would be predicted based on fresh crop residue does not necessarily apply to the no-till soil, since changes in the chemical and physical composition of the standing straw will occur due to weathering over the fallow period.