Barley growth and development
The barley crop goes through three distinct phases as it grows from planting to harvest. These phases can be described as foundation, construction and production.
High yields and good grain quality will only be achieved if ‘inputs’ are targeted towards the key periods of crop growth and development. There are a number of key growth and development targets that can be used as benchmarks in achieving high yield and quality. The barley crop goes through three distinct phases as it grows from planting to harvest:
Barley development phases
Foundation
The foundation phase starts from sowing and lasts through to the start of stem extension. During this time, yield-bearing shoots / tillers and primary roots form as the canopy develops. The components of yield (ear numbers and grain sites /m2) are set by the end of this stage. The speed of growth will depend on the environment with dull, cool days giving slow growth.
As the soil temperature cools down (winter crops) or warms up (spring crops) the speed of establishment varies. Late September or early October sowings give optimal establishment with 50% emergence occurring in 15-20 days.
As the soil temperature warms up, the speed of emergence increases. Achieving a good spring plant population of 300-350 plants / m2 is very important as barley has a very limited ability to compensate for low populations with large grain numbers in the ear.
Construction
The construction phase starts from the first node being detectable through to flowering. This is a critical growth period as yield delivering leaves, deep roots, fertile florets and stem reserves form. Ear numbers in barley is of more importance than in wheat as barley only has one floret / spikelet giving very limited room for compensating a low ear number with more grains/ear. Two row barley has one spikelet either side of the rachis and six row barley has three spikelets either side.
By Zadoks GS 31 a Green Area Index of three should be achieved giving complete ground cover and 75% light interception. At GS 59 a Green Area Index of 6 will be achieved giving 90-95% light interception. Growth is very rapid with high daily nutrient demand from the soil.
Production
The production phase starts after flowering, lasting through to the grains filling and ripening. Barley is different from wheat (especially spring barley) as flowering can start just prior to ear emergence. During this period the critical yield components i.e. final number of grains /m2 and the grain weight will be determined.
The number of grains on each ear depends on the number of fertile spikelets on the central ‘stem’ or rachis of the ear. In barley, each spikelet contains one floret. In two-row barley, the spikelets form in threes with only the floret in the central spikelet being fertile. In six-row barley, florets in all three spikelets are fertile. Crop management, and particularly nutrition, can significantly influence grains/ear and ears/m2. Grains/m2 and the size of individual grains determines the storage capacity during grain filling.
Leaf area is made up differently in barley, each successive leaf has a smaller area with the final flag leaf representing 4% compared to the 16% of leaf 5. The ear with the awns is very significant with it representing 11% of the green area. Maintaining the health of all the leaves and awns is critical to maximize grain development. Plant stem carbohydrate reserves are also important and act as a buffer against stress conditions experienced by the crop, such as drought. Up to 50% of yield can come from these reserves which build up and reach their peak shortly after flowering.
Barley growth stages
The development of barley can be described using a number of scales that have been defined over the years. There are typically three used: Zadoks, Feekes and Haun, with the Zadoks being the most widely used to help ‘input’ management decisions. Below is the scale in detail.
