Corn Growth Stages Chad Lee, Ph.D. Grain Crops Extension Specialist University of Kentucky Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky All growth stages presented here are based on… How a Corn Plant Develops, Special Report No. 48 Iowa State University Press $2.00 Extension Distribution Center 119 Printing and Publications Building Iowa State University Ames, Iowa 50011-3171 Telephone: (515) 294-5247 Fax: (515) 294-2945 http://www.extension.iastate.edu/pubs/Order.html The material in this presentation comes from Iowa State Special Report No. 48. This is an excellent resource for any producer or agronomist. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky http://maize.agron.iastate.edu/corngrows.html#stages Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Vegetative Stages Reproductive Stages VE emergence R1 silking V1 first leaf R2 blister V2 second leaf R3 milk V3 third leaf R4 dough V(n) nth leaf R5 dent VT tasseling R6 physiological maturity * When staging a field of corn, each specific V or R stage is defined only when 50 percent or more of the plants in the field are in or beyond that stage. http://maize.agron.iastate.edu/corngrows.html Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Development of Nodal Roots How a Corn Plant Develops, Special Report No. 48, Iowa State University, 1998 Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Growing point is below the soil surface. Frosts on the surface will not kill the plants. Freezing soil temps will kill the plant. Flooding can kill plants. Root hairs begin to form on Nodal Roots. Seminal Root growth has basically stopped. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Tassel development has started. Ear shoot formation has also started. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky V6: Typically when lower leaves begin to tear off of stalk. To be certain about V-stages beyond V6: Split the entire stalk (from the tip to the roots) in half with a knife. The first five nodes will be clustered near the bottom of the stalk and the 6th node will be very close to the soil line. Count nodes above the 6th node to determine how many nodes are present. The total number of nodes equals the V-stage of the plant. For example 7 nodes = V7 corn. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Ear shoot. Growing point is above the ground. Nodal Root System is the primary root system for nutrients and water. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Premature Tassel Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Growth rate rapidly increases. Greater demand for nutrients and water. Ear shoot. Ear shoot. Growing point. Ear shoot. Grain Crops Extension, University of Kentucky

Both kernel size and kernel number are being determined. V12 Both kernel size and kernel number are being determined. Any limits on water or nutrients at this phase will drastically impact yields. Earlier maturing hybrids will pass through this phase faster than later maturing hybrids. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky About 10-12 days from silking. Entering the most critical stage for yield determination. The plant is most sensitive to water and/or nutrient stress at this stage. Irrigation- the 4 weeks around silking are the most critical. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Ear shoots near the top of the plant are starting to out-grow ear shoots lower on the plant. Lower part of plant Upper part of plant Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Lower part of plant Upper part of plant Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Lower part of plant Upper part of plant Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky VT - Tassle Occurs when last branch of tassel is visible but before silks emerge. Most susceptible to hail damage at this stage. Complete leaf loss at VT will result in little to no yield. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky VT Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Pollen shed Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky R1 - Silking Silks starting to emerge. N uptake is rapid. P uptake is rapid. K uptake is nearly complete. Watch for corn borer feeding. Moisture is needed for pollination. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky R1 - Silking Cob material Premature kernel Two to three days are required for all silks on an ear to be pollinated. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky R2 - Blister Ear size is nearly complete. Fertilized silks are starting to dry out. An miniature corn plant has started to develop within the premature kernel. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky R3 - Milk Kernels are becoming yellow on the outside. Silks are dry. Kernels are at 80% moisture. Stress becomes less of a factor as kernels start to dry down. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky R4 - Dough Fluid in the kernel is becoming a consistency similar to dough. (70% moisture) Almost ½ of the dry weight has been accumulated. Five embryonic leaves have formed in the kernel. These will be the first five leaves of a new plant as it emerges next year. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky R5 - Dent Most of the kernels have dented on the top. Most kernels are about 55% moisture at the start of R5. A starch layer has formed and begins to progress down the kernel. A frost will stop dry matter accumulation and reduce yields. Grain Crops Extension, University of Kentucky

R6 – Physiological Maturity Blacklayer Grain Crops Extension, University of Kentucky

R6 – Physiological Maturity Kernel is about 30 – 35% moisture. Kernels need to be at 13 to 15 % moisture for safe storage. Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky Vegetative Stages Reproductive Stages VE emergence R1 silking V1 first leaf R2 blister V2 second leaf R3 milk V3 third leaf R4 dough V(n) nth leaf R5 dent VT tasseling R6 physiological maturity * When staging a field of corn, each specific V or R stage is defined only when 50 percent or more of the plants in the field are in or beyond that stage. http://maize.agron.iastate.edu/corngrows.html Grain Crops Extension, University of Kentucky

Grain Crops Extension, University of Kentucky