Test mineral N to fine-tune applications

SOIL MINERAL nitrogen tests are helping Lincs grower Andrew Ward fine-tune nitrogen applications, as well as make sure grain quality specifications are met.

As host of last year”s Cereals Event, land at Glebe Farm, Leadenham, was tested as part of a national initiative, but he admits the results proved very useful.

“We were growing a Group 2 milling wheat, Cordiale, in the first wheat position, after oilseed rape,” recalls Mr Ward. “That was an unusual situation for us, as our milling wheats are normally second wheats.”

In addition to being unfamiliar with how much nitrogen would be needed to reach the required 13% protein in a first wheat, he also had to take into account the previous oilseed rape crop”s poor ability to use applied nitrogen and the use of biosolids on the field.

“The results came back lower then expected,” he says. “They arrived with a comparison for other parts of the country, which was interesting, and gave us the necessary figures of how much soil nitrogen was available to the crop.”

Armed with this, he calculated the additional bagged nitrogen required to reach his yield and quality targets. “It”s a case of simple maths once you know what”s already there and what you”re aiming for.”

The breakdown supplied by Anglian Water showed that a typical 19t/ha application of biosolids supplied a total of 180kg/ha of nitrogen, of which 26kg/ha was available in the first year. “Including that amount, the Cordiale received a total of 236kg/ha. It yielded 11.2t/ha and the grain protein was between 13.2 and 14.3%.”

The target for top yielding feed varieties is 12t/ha at Glebe Farm. Mr Ward will be using soil mineral nitrogen tests to adjust nitrogen use on Brompton being grown for seed this year, as it is following a crop of spring beans.

“These tests make sure we are not wasting inputs, or failing to apply enough fertiliser for the desired end market,” he points out. “They”ve helped make fertiliser application even more accurate on this farm.”

Nitrogen use on spring barley has been increased to ensure there is enough to feed yield. “We don”t want to exceed a grain N target of 1.7, but we found we had to up the nitrogen to 140kg/ha on Optic and Cocktail.”

Nutri-Bio has been used at the farm since 2002 and is applied before beet and oilseed rape. Every field is sampled by Anglian Water before application and an analysis of the nitrogen, phosphate and potash supplied is given in kg/ha.

“It’s naturally high in phosphate and helps put organic matter back into the soil,” remarks Mr Ward.

He is convinced cross-compliance will mean having to justify every input and believes soil mineral nitrogen tests will be important. “Once soil management plans are introduced next year, this is just the sort of detail we will have to supply.”

He estimates the cost of a soil mineral nitrogen test is equivalent to 42kg of nitrogen (with ammonium nitrate at 140/t). “They”re good value for money. Using them in strategic places in the rotation gives you the justification for application rates. Hitting the end market specifications becomes easier, too.”

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