Crop notes May 2008

High wheat prices and poor returns from beef enterprises have resulted in the largest area of winter wheat crops planted in N. Ireland for more than fifteen years. Much of this area has been planted by first-time growers and they have had presented many queries over the past few weeks to me and colleagues at Greenmount Campus. With this in mind, I think it is worth taking a look at disease control which, after nitrogen inputs, gives the best return on investment, and on average, can increase yield by 35 percent. The following are some of the more frequently asked questions I’ve received from experienced growers, as well as those new to wheat farming.

Fungicide applications are the best value crop protection input often giving four fold returns. On average wheat prices would have to fall to £32/tonne before fungicides would become uneconomic on average. Maximum returns come from the lowest-cost-per-tonne production. Fungicides increase yield and reduce the variability of yields, giving a more consistent margin.

Even the least responsive variety gave a 20 percent response to fungicide application. Variety is only one factor; year and moisture availability can have even greater effects, making input prediction difficult. The decision on spend should take account of the whole picture of potential response to fungicide programmes. Season is the main factor which determines the response to fungicide application.

No. Generally it is more cost-effective to use a more active product at a lower dose than to use a high dose of a less effective product.

Fungicides with the best activity on Septoria (our major disease) are based on two actives…prothioconazole (for example, Proline or Prosaro) and epoxiconazole (for example, Opus, Mantra, Capalo or Tracker)

Diseases will be present even if you can’t see them. Prevention is more effective and cheaper than cure. Dry conditions at the key target growth stages can sometimes lull growers into thinking that the perceived disease threat is low but this can change quickly.

T1 (early stem extension, late April/ early May). Essential. Sets the crop up and maintains potential yield

T2 (flag leaf emergence, late May/ early June). Essential. Keeps the main yield producing leaves free of disease.

T3 (ear emergence, mid June). Very important. Prevents the crop from late yield robbers and maintains grain quality

Doses affect the diseases controlled, the length of protection, the level of curative control and ability to generate green leaf and ultimately yield. As a rule of thumb the dose of T1 and T2 fungicides should not be reduced to obtain the optimum economic benefit.

From four years of benchmarking results across N. Ireland we have found consistently that the most profitable growers time their nitrogen top dressing at the two-three leaf stage (GS 12-13). Later applications than this may green the crop but add little yield. You should also avoid excessive applications of nitrogen, and keep the right side of the law, by fully taking into account any organic manure applications or nitrogen contribution from previous cropping.

Aim to apply a mixture of at least two broad-spectrum herbicides whenever most of the weeds are at the two-four leaf stages. This will ensure that weed competition is removed at an early stage of crop development, and may allow a reduced rate of product to be used.