Low-down soil sampling for high rewards
Low-down soil sampling for high rewards
Soil analysis is showing its worth on farmers weeklys
eastern barometer farm where Autocasting rape is also
proving a success. Andrew Blake reports from Essex
DEEPER soil sampling at Waltham Hall, Takeley this season appears to have been a good move, say John Latham and independent agronomist Jamie Mackay. It has uncovered high nitrogen reserves which should allow inputs to be managed better.
oil mineral-N testing to a depth of 60cm (2ft) was introduced last year after Mr Latham introduced dried sewage sludge in the form of Terra cake.
Only two fields were assessed this spring, both first wheats, but the results are proving useful (see table).
"This year we have gone down to 90cm and it looks to have been extremely worthwhile," says Mr Mackay. "There is clearly a huge slug of available N down there in some Malacca wheat, both from the oilseed rape and the cake which went on the rape stubble. We wouldnt have picked it up if we had only gone to 60cm." Some sampling systems work to only 30cm (12in), he notes.
The finding should allow useful fertiliser savings to be made. September-drilled crops will soon be reaching the deep nitrogen, he believes.
Total reserves in a field of Riband after peas which received sludge cake eighteen months ago are only about half that under the Malacca. But they are much higher than elsewhere where Mr Mackay sampled a couple of fields in a run of cereals to get a better idea of malting barley needs.
The 88kg/ha (70 units/acre) of N is more than would have been expected after peas alone, but understandable given leaching effects of the wet winter which included 75mm (3in) of rain in February, says Mr Latham. "It is a logical result."
The cake, delivered and spread at 50t/ha (20t/acre) for about £25/ha (£10/acre), also went onto about two-thirds of the Consort second wheats. The crops rapid greening before top-dressing has been particularly encouraging. "This summer I hope all the second wheats will get it."
Take-all and eyespot remain at very low levels, notes Mr Mackay. "Dried sludge does seem to have some yield-enhancing qualities other than just nitrogen. Its possible that the extra phosphate might be helping to improve root growth."
However application policy may change. One reason for applying it to the rape stubble was to widen the window of opportunity for Thames Waters spreaders. "Their delivery slots are very tight," explains Mr Latham. "But I think it has fewer advantages in first wheats."
The apparent early N uptake in all the treated fields has eased pressure on first top-dressings, and the initial application on second wheats will probably be trimmed to 40kg/ha (32 units/acre) from the more usual 70kg/ha (56 units/acre) to account for it.
"On the Malacca after the cake we probably shant need anything until mid-April."
Working on the basis that each tonne of grain merits 30kg/ha of N for yield alone, the sampling and Natural Resource Managements analysis suggests about half that crops needs can be met from the soil, Mr Mackay estimates.
"There is quite a lot of time and effort involved. We allow 1-2 hours for each field sample. But it is giving us a much better handle on how to manage these crops."
Despite a fully comprehensive growth regulator programme last season one field of cake-treated Rialto still lodged, he notes. "If we had picked up on the deep nitrogen we might have avoided the lodging."
Mackay Agronomy soil mineral N tests (kg/ha)*
0-30cm 30-60cm 60-90cm Total
1st WW after OSR + cake 99 9.5 48.7 91.8 150
1st WW after peas + cake 98 13.6 38.6 35.3 88
4th year cereals (field A) 9.6 10 12.2 32
4th year cereals (field B) 3.9 6.8 6.5 17
* Samples taken Feb 29
Soaking up the N – this Malacca wheat wont need any bag fertiliser until the middle of next month thanks to good soil reserves, say eastern barometer farmer John Latham (right) and adviser Jamie Mackey.
SPRINGFERTILISER
• Deeper min-N testing.
• Pinpointing useful reserves.
• Sludge cake effects
• Top-dressing adjustments.