Improving the value & sustainability of Esperance port zone grain growers.

Barley straw strength and head loss

 

By: Andrea Hills, Barley Research Officer DAFWA Esperance

In areas where good growing conditions lead to tall plants, variety straw strength, also known as the lodging risk, is important. Lodging does not necessarily occur every year or across entire paddocks. Other than naturally tall plants, high nitrogen applications tend to increase the likelihood of lodging, along with extremely windy conditions during grain filling and ripening. Barley varieties differ widely in their straw strength, ranging from very robust types such as Capstan and Baudin, to those that readily lean and may even collapse, such as Gairdner. Sometimes the collapse is so bad that all or a portion of the crop cannot be harvested, hence lodging can significantly reduce grain yields.

Head loss is when the straw of plants may remain standing but breakage immediately under the head or even a few inches below the head occurs and the heads fall to the ground, reducing grain yields. While this trait is under genetic control, weather conditions such storms or high winds greatly exacerbate the problem. Baudin is excellent at holding onto its heads but Gairdner and Buloke are at risk of head loss. As armyworm also drop heads onto the ground, it is worth looking closely at areas where heads are being lost for evidence of armyworm. While the caterpillar itself can be difficult to find in a crop, on the ground its faeces can readily be seen and they look like small green-black squares (‘hay bales’) on the ground. Three large armyworm / m2 of crop can cause substantial head loss and controlling them is worth considering.

In the past when varieties likely to lodge and/or lose heads were grown in the medium to high rainfall areas of the south coast, swathing (or windrowing) of barley to reduce the risk of yield losses was common. This requires the grower to monitor the crop and swath when the peduncle (the stem below the head) had turned a straw colour as this loss of green means that the crop has finished grain filling. Swathing too early while the crop is still moving assimilates into the head can result in some loss of grain yield. Other than preventing lodging and head loss, benefits of swathing include less time until the crop is ready harvest and a lower moisture content after rain or humid weather so harvest recommences earlier relative to standing barley.

The use of growth regulators to reduce the risk of lodging and head loss is effective. This works by shortening up tall varieties and by thickening the stem wall it strengthens the straw. Current costs of these prevent their wide scale use.

Variety selection by growers often takes the twin risks of lodging and/or head loss into consideration. DAFWA’s Barley Variety Sowing Guides have information on the relative performance of varieties for these characteristics under WA growing conditions.

 

Armyworm larvae; their distinguishing feature are the three white stripes on the neck.