The Effect of Tillage System and Proceeding Crop on Phosphorus Response of Flax
Assess the interactive effects of tillage system, preceeding crop and P management on flax production.
IPNI-1999-CAN-MB11
15 Mar 2001
Justification
- Phosphorus fertilization of flax can be problematic, since flax is very sensitive to seed-placed applications of monoammonium phosphate. Banded applications of P fertilizer are not generally used effectively by flax unless they are positioned within 2.5 to 5.0 cm of the seed-row and broadcast applications of P tend not to increase flax seed yield. Therefore, unless a producer has access to seeding equipment capable of side-banding fertilizer, P fertilization of flax is frequently ineffective. In 14 site years of research in Manitoba and Saskatchewan, the P response of the best treatment in the experiment exceeded 3 bu/acre in only 3 instances. Producers frequently avoid P application in flax and increase the P supply in the preceding crops, in order to supply residual P for use by the subsequent flax crop.
Mycorrhizae are fungi which form associations with certain crops under low-P situations, enhancing the uptake of P by the crop. The greater P absorption is largely a result of the undisrupted mycelium present in an undisturbed soil. The mycelium remains viable over extended periods in frozen soil and so can acquire P from the soil and deliver it to the plant immediately upon becoming connected to a newly developing root system in the spring. Phosphorus status of the crop in the first 4-6 weeks of growth has a major impact on final crop yield. Flax is a highly mycorrhizal crop. It is possible mycorrhizal associations could be responsible both for part of the positive response that flax shows in no-till systems and for the limited P response observed in recent studies. If so, P fertility requirements in flax could be greatly affected by tillage system and by whether the preceding crop was mycorrhizal or not. Phosphorus fertilization could possibly be reduced or eliminated in flax grown in no-till following a mycorrhizal crop and optimized in flax grown on summer fallow, after a non-mycorrhizal crop, or under conventional tillage management. By more clearly defining the P requirements of flax, canola and wheat grown under different management systems, we may be able to reduce inputs while maintaining or improving crop yield and quality.
Information on the interactive effects of tillage system, preceding crop and P management on flax production is lacking. It may be possible to improve flax yields by selection of preceding crop in rotation and supplying P for flax by high applications in the preceding crop.