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Agronomics and economics: A few graphs of interest

At the Manitoba Agronomists Conference in December, Roy Arnott and Anastasia Kubinec of Manitoba Agriculture gave a joint presentation titled Agronomics & economics — crop management decisions need both! The full presentation is available on the Manitoba Agriculture website, but here are a few snapshots.

Crop rotation can pay

The above charts by Anastasia Kubinec are based on provincial crop insurance data showing the yield effect of planting on different stubbles compared to the most recent five-year average. For example, planting spring wheat after spring wheat cuts yields by 15 per cent, but planting it on soybean stubble gives an eight per cent boost. The second chart shows the returns for various six-year rotations using that data. Assuming projected per-acre returns for 2017, a canola/wheat rotation returns $1,090. Introducing two years of soybeans boosts that to $1,127 and a winter wheat/soybean/oat/canola/winter wheat rotation returns $1,223.

Cheaper in the fall?

It’s an old question — is fertilizer cheaper in the spring or in the fall? The answer: In the fall — usually. These charts prepared by Manitoba Agriculture’s Roy Arnott show the trend since 2001 for 46-0-0 and 11-52-0. On average, spring nitrogen prices are 13.3 per cent higher and spring phosphate prices 16.6 per cent higher over that period. The trend is even more clear if you exclude the sharp price changes in 2008 and 2009.

When is the best time to seed?

Using Manitoba crop insurance data, Anastasia Kubinec prepared this graph showing the relationship between seeding date and yield. The vertical blue line shows the average date of Manitoba’s last killing frost, which is the third week in May. If you had to reseed after that date, canola is the clear winner, holding yield relatively well into early June while other crops fall off more sharply.

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