I am pleased to put up my second invited guest post on this blog. The article discusses identification of crop staging of cereals. It is a timely article as we are moving rapidly into fungicide season. Cereal crop staging can be a little ambiguous and tricky when trying to project and plan the timing of fungicide operations. We consulted with Cory Jacob a week or two ago because of the atypical (at least for the last 7 or 8 years) and variable pace of crop development we were seeing in the 2015 cereal crop – we wanted to be certain we were interpreting our observations properly. I thought it would be a great topic for a blog article….so here we are.
Cory works as a Regional Crops Specialist with the Ministry of Agriculture out of Watrous. He carries in his back pocket both agronomy based Bachelor’s and Master’s degrees from the University of Saskatchewan. He has held various summer agronomy themed jobs in private industry and also has experience as a graduate teaching assistant at the University of Saskatchewan. Cory works closely with producers and industry to help alleviate current and future issues in crop production.
Cereal crop staging – Cory Jacob, Saskatchewan Ministry of Agriculture, Watrous, SK
Leaves and tillers
Cereal crops are easily the most difficult to stage. When staging a cereal crop, it is good to know that the leaves develop on alternate sides of the stem. What I mean, is that the first leaf will be on the left side of the plant and the second leaf on the right side and so on.
The best way to stage a cereal crop is to first, take all of the leaves or stems in your hand and see which is the tallest, the tallest stem is the main stem as it is the furthest along in growth and development. Next is to identify the leaves, the first leaf will appear on the left side of the plant and will have a blunt or rounded tip and will be the lowest leaf on the left side of the plant.
Tillers can be considered as side shoots off of the main stem leaves and have their own sheath called a prophyll. Typically, the coleoptilar tiller, which is formed from the coleoptile node, on the seed, this tiller develops at any time regardless of the plant development. The tillers that form from the leaf axil (where the main stem and leaf blade meet) emerge after the plants has 3 leaves and will develop in order of the true leaves, so tiller one will emerge from the axil of leaf one and so on. Typically, 5 tillers is the maximum observed on a plant.
In general, every 3-4 days a new leaf will emerge on a cereal crop plant, but this is a factor of many things including growing degree days, environment, genetics, fertility, crop stress, etc.
Head initiation takes place during the 4 leaf stage and before stem elongation begins. If you were to cut the stem open, you will find the head developing within the stem. Once the formation of head is complete, stem elongation (jointing) begins and this pushes the wheat head up in the plant. Stem elongation beings around the 5 or 6 leaf stage. There are 7 nodes with in a cereal plants, 4 remain below ground in the crown area, the 5th one remains around the soil surface and elongates only slightly, which the 6th and 7th nodes elongate well above the soil surface, which pushes up the head. The peduncle (stalk leading to the head) is the longest internode.
The flag leaf is the last leaf to emerge before the head. Typically, the 6th leaf is the penultimate leaf (leaf right below the flag leaf) and the 7th leaf is the flag leaf. This can greatly differ, but can be a general guideline. The flag leaf will begin to emerge just after the 3rd (7th) above-ground node is observed. The flag leaf accounts for about 75 percent (generally) of yield, so it is best to protect the flag leaf with a fungicide application.
The boot will swell after flag leaf development and the peduncle will elongate. The flag leaf sheath will swell to form the boot and the flag leaf collar and sheath will be forced open by the developing head.
Heading occurs as the peduncle continues to elongate and push the head out of the fag leaf collar. In barley, the crop flowers just before or during head emergence, other cereal crops will flower after head emergence. Typically, wheat will flower 3-10 days after head emergence. The head of the cereal crop develops from the middle out and the color of the anthers is very important for flowering. The anthers is what you will see hanging off of the wheat head. Green anthers mean that flowering has not occurred yet and yellow or gray anthers mean that flowering has occurred. During flowering (anthesis) is the ideal time to spray for Fusarium Head Blight, as it is a tight window to hit all of the acres at the ideal stage, it is recommended to begin spraying when you see 75% if the heads on the main stem fully emerged. Perfect timing will be when just a few yellow flowers can be observed in the middle of the wheat head. A producer should stop spraying when they notice that 50% of the heads on the main stems are in flower. It is too late to spray once you see the anthers turn white and dry up, this means flowering is complete and it is too late to spray, or rather spraying will provide little benefit. (FHB infographic place here)
For grain development, the watery ripe stage occurs when a clear fluid can be squeezed from a developing kernel. The plant will be green and the lower leaves will begin to die off. Soft dough stage is when the material pressed out of the kernel is no longer a liquid and is a meal or dough consistency. Hard dough stage is when the kernel reach physiological maturity and little green color remain in the plant. Kernel hard stage occurs when the plant has become completely yellow and the kernel has become firm. The surface of the kernel can be dented with the edge of a thumbnail. Harvest can occur on the kernel is hard and the plant has become dry and brittle.