Getting the nutrition of winter rye crops right
Teagasc research scientist, Dr. Richie Hackett, has confirmed a number of priorities when it comes to the nutrition of winter rye crops.
The cereal is relatively new in Ireland in the modern era, although it was grown in the past.
However, the area of rye planted out in the country has increased steadily over the last number of years: albeit from a low base.
According to the Teagasc tillage specialist, the crop is reputed to tolerate a wide variation of soil pH values with the range of 6-7 being optimal.
Dr. Hackett explained: “Rye has been shown to have an extensive and deep root system that is good at scavenging nutrients and water, making it a better crop option on poorer, more drought-prone or less fertile soils than wheat or barley.
“Its high yield and particularly its high straw yield means that it has a relatively high demand for nutrients.
“The basics of nutrition of the rye crop will be similar to other winter cereals.
"Nutrient requirements should be based on soil and/or foliar tests and expected offtakes with the overall goal of replacing offtakes of the major nutrients so as to maintain soil levels.”
Research at Oak Park has indicated that hybrid rye has a higher nitrogen (N) use efficiency than winter wheat, typically requiring 20-25% less fertiliser N than wheat in Index 1 situations.
In addition, there is some evidence that suggests that the difference between wheat and rye may be smaller when sown after a break crop.
Nitrogen
This high nitrogen use efficiency coupled with high yields contributes to rye having a low carbon footprint.
“Rye can move through growth stages earlier than for other crops in the spring and will have a greater demand for N earlier in the season," Dr. Hackett said.
"This might indicate that very early N application, possibly in February, may be required."
However, work at Oak Park indicated very little difference, in terms of grain yield, between applying the first N in late February/early March and mid-March on well established crops.
Early N application will encourage a more dense canopy which can exacerbate lodging risk.
Crops with low tiller numbers or crops that are being grazed by slugs may benefit from earlier N applications.
Irish trials have confirmed that a two or three split programme is suggested with the first, comprising of 25-30% of the total, being applied in early to mid-March and the remainder being applied at around growth stage 31 in late March or early April.
While a third application generally does not give a yield advantage over a two split programme, it can avoid the need to apply a large second application and can also reduces the risk of N loss due to leaching as a result of a large second application followed by unfavourable conditions.
Where a third application is being applied it can be applied at around flag leaf emergence.
For soil N index 1 situations, where no organic manures have been applied, a total of 175kg N/ha is suggested. On sites with reduced yield potential, this can be reduced by 10-20kg N/ha.
“Lower amounts will help reduce any risk of lodging. Rates in excess of 200 kg N/ ha significantly increase the risk of lodging," Dr. Hackett said.
“If organic manures are applied, it is essential that the amount of fertiliser N applied is reduced by an amount equivalent to the available N in the manure to reduce the risk of lodging.
“The risk of lodging is likely to be very high where rye is grown in a soil N index 4 situation, particularly if the crop is sown early in the autumn.”
Meanwhile, organic manures can be a useful and cost effective source of nutrients.
Organic manures with high proportions of available N such as slurries, poultry manures or digestate should be applied in the spring to maximise the use of the nutrient in these products.
Minerals
There is no Irish research available to date on the phosphorous, potash, and sulphur requirements of rye.
Phosphorus offtakes will be similar to other cereals in terms of kg of phosphorous per tonne of grain yield.
Given its high straw yield, potassium offtakes are likely to be higher than for winter wheat or barley.
But there is conflicting evidence from abroad as to the concentration of potash in the straw.
In the absence of Irish data, similar potassium inputs to winter oats are suggested.
The sulphur requirements of rye crops are similar to other cereals and 15-20kg of sulphur per hectare is advised.
Trace element inputs should be based on soil tests and known deficiencies and appropriate foliar or soil applications made accordingly.
