Variable rates of N applications pay off in spuds
Variable rates of N applications pay off in spuds
By Charles Abel
PRECISION farming tools are bringing increasingly profitable responses to arable farms, including higher potato yields and reduced liming costs in cereals, the Shuttleworth Precision Farming Alliance conference heard last week.
Scope for in-season input adjustments using Hydros Precision N sensor look good, Yorks farmer, contractor and precision farming enthusiast Clive Blacker told delegates at Shuttleworth College, Beds.
Last year the tractor-mounted sensor was used to detect potato vigour and vary Nufol liquid nitrogen rates accordingly. Application maps were created using N Sensor data gathered during blight spraying for a highly variable field in the Vale of York. A 10t/ha (4t/acre) yield boost followed.
While acknowledging that uniform applications of Nufol may have also boosted yield, Mr Blacker believed that the sensor brought extra benefits by matching N rate to precise crop need across the field. "On this land soil type can vary from blow away sand to clay in meters. In the variable bouts N rates ranged from 8kg/ha to 20kg/ha according to crop greenness."
Most of the yield benefit was in marketable sized tubers. However, variety and timing will need considering – benefits in Dell were not mirrored in earlier maturing Estima, he noted.
The N Sensor was not calibrated for potatoes, so there is clearly scope for further potential, he continued. Potato calibration should be available this season, commented N Sensor supplier, Hydro.
Varying desiccant rate according to crop density and greenness could also pay, Mr Blacker added. "We scanned a rape crop at desiccation last year and the map tied in very well with the final yield map. It picked out trends we did not think it would." Variable rate or patch desiccation of strobilurin-greened cereals may also be worthwhile.
Meanwhile, farm manager Bill Gray improved lime use on his unit near Edinburgh and cut costs by soil sampling sandy clay loams on a 50m grid. One field previously managed as pH6.3 was found to vary greatly, 4% falling below pH5.75 and 35% over 6.5.
Adjusting lime rates accordingly saw rates vary from 2-8t/ha, with less lime used overall and a £362 saving after sampling and testing costs.
In another field rates varied similarly, but overall lime use remained the same. Despite that, Mr Gray was satisfied. "At least we know low pH areas are getting enough lime and we are not wasting it elsewhere. It will be interesting to see the results when we resample."
He also called for simpler sampling. "It needs automating to make it easier, so the information is more available to use in our crop management." He also stressed the need to standardise soil analysis. "All the labs are doing it their own way, with no standardisation. It is something we should think about." *
PRECISIONBENEFITS
• Variable late N boosted potato yield 10t/ha.
• Extra yield mainly in marketable tubers.
• Variety and timing key.
• N Sensor calibration for 2000.
• Variable desiccation could pay.
• Big liming benefits in Scotland.
Clive Blacker – variable rate N boosted potato yields. Variable rate rape desiccant could be next.
Bill Gray – big savings on lime use, but keen to see standardised soil analysis.