While strong demand is creating a valuable market for straw, growers are being warned that if they do cart straw from their fields they’ll need to replace base nutrients if following crop yields are to be maintained.

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"As a result, and taking into account lower grain and straw yields likely this season, they stand to gain over £200/ha for their straw," he calculates.  "In effect, this will more than off-set the 1t/ha yield loss many anticipate from their cereals due to early season drought this harvest.

"However, if they do opt to bale rather than chop and incorporate, expect to need to spend £25-30/ha in replacing the potash, phosphate and magnesium carted off the field with the straw.

"Furthermore, with the latest Professional Agricultural Analysis Group (PAAG) figures suggesting that around 30% of arable soil samples analysed are below the recommended index for K, it is becoming even more critical to accurately assess needs and replace dwindling nutrient reserves."

According to Mr McHoul, technical manager with fertiliser specialists, K+S UK & Eire, new RB209 figures suggest that for every tonne of grain produced, the plant generates half a tonne of straw containing 4.8 kg/K20. 

"So, with potash at around £350/t, an 8t/ha crop with the straw baled and carted away will remove 38.4kg of potash (K2O) worth £22/ha.  At the same time, growers will also need to replace significant, but smaller amounts of phosphate and magnesium if modern high yielding cereal crops are to reach full potential."

Mr McHoul points out that arable farmers need to be maintaining soil P & K indices at a minimum of 2 (2- for K) or higher.  Letting these slip any lower will bring poorer performing crops and compromise the efficiency of any nitrogen applied. 

"Those who have taken a recent potash 'holiday' and that are below index 2 will almost certainly have seen the effects of this year’s spring drought exacerbated due to compromised water use efficiency.

"As a rule of thumb, baling removes double the amount of potash compared to that where straw is disced and put back into the soil system," he points out.  "At the same time, growers need to weigh up the costs of lost organic matter from carting straw off the field.

"Conversely though, straw incorporation does have its downsides, including the power and additional time needed to chop the straw on the combine, together with issues of the trash at cultivation and drilling, with greater pest and disease control often required."

"So, to summarise, this year it looks tempting to sell straw due to the strong demand.  The figures, even when you include time and energy costs still stack up favourably but growers should remember to replace the additional nutrients lost from the field."