On-farm trials are important to Farmers Weekly‘s Arable Farmer of the Year. Andrew Blake relays results from some of last season’s Lincolnshire tests.

Last season’s return to soil mineral nitrogen testing produced some surprising results in Andrew Ward’s annual on-farm experiments at his Glebe and Heath Farms, Leadenham.

“We tried it four years ago and I wasn’t convinced of its value. But a FACTS course made me realise that we must justify our inputs. So I thought I’d look again. I was sceptical when GrowHow’s results came back because the N recommendations were so much lower than we’d normally apply.”

The main heathland Oakley, receiving the recommended 126kg/ha of N in two dressings of urea, yielded only 10.8t/ha – 1.1t/ha less than the rest of the field that got the more normal 164kg/ha. The net loss with wheat at £90/t and urea at £203/t was £70/ha.

“However, the crucial thing to get right is the projected yield, which, as was proved this year, is very difficult.

“With the Oakley I said this would be 11t/ha. If the actual yield of 11.9t/ha had been entered in the GrowHow N-Min system, the recommendation would have been for 158kg/ha not 126kg/ha. And if the yield had also been 11.9t/ha, the loss of £70/ha would have turned into a profit of £2.64/ha.

Latitude pays dividends

A separate trial in 2007/8 highlighted the value of Latitude (silthiofam) seed dressing on Glasgow as a second wheat.
Sown on 21 Oct at 270 seeds/sq m on heavy land, the only agronomic difference in inputs between the main field and the trial plot was that the seed in the latter was dressed with Latitude as well as Redigo (prothioconazole).
The Latitude dressed area gave 11.33t/ha, which was 0.59t/ha more than that dressed with Redigo alone.
The Latitude was £155/t, which at the 114kg/ha seed rate added £17.67 to the overall cost. But with grain at £90/t there was still a useful margin of £35.43/ha from the treatment.

“The N-Min programme is only as good as the information that is put in, so this must be highly accurate, but also realistic.”

On two heavy-land fields, one of Humber after HOLL rape, the other Monty after spring beans, there were only marginal yield advantages from his higher rates (see table). On the Monty the N-Min approach was more profitable. All the harvested grain nitrogens were about 1.96%, he notes. “So none of the N inputs were over the top.

“Of course, these are only one season’s results and we must bear in mind the environment,” says Mr Ward. “Perhaps we need to look at our timings again and maybe split our dressings more – until now we’ve used just two applications.

“I shall continue with the GrowHow N-Min testing, especially with the way the fertiliser price has gone, and the levels of N that we put on gave us a considerably higher yield and a better margin in two of the three trials.”

Realistic yield targets are just one aspect when calculating fertiliser rates using the GrowHow N-Min and N-Calc service, says the firm’s Dave Towse. “But they are an important part because we know that for every extra tonne of yield, the crop will need about 25kg/ha of nitrogen.

“In the Oakley, the N-Min N-Calc system recommended a 126kg/ha fertiliser based on an anticipated yield of 11t/ha and it delivered at 10.8t/ha. But as Andrew discovered this season, 11t/ha turned out to be an underestimate.

“In the other two trials, Andrew’s yield aspirations were higher – at 12t/ha – and the GrowHow service delivered yields of 12t/ha and 12.42t/ha, respectively.

“Interpretation of N-Min results is critical. Soil type, depth and stone content can all have an impact on fertiliser requirements affecting financial and environmental costs.”

 

Glebe Farm N rate (kg/ha) trials on winter wheat

Crop

Rate

Yield (t/ha)

Net result £

Oakley

Field

164

11.9

 

Plot

126

10.8

-£70/ha

Humber

Field

164

12.3

 

Plot

135

12.0

-£15.11/ha

Monty

Field

174

12.56

 

Plot

135

12.42

+£2.82/ha