Battle for the Belt: Season 2, Episode 17 – Crop Progress Update

Episode 17 of Battle for the Belt is now available: https://www.youtube.com/watch?v=hHBjPAml2uM

In Episode 17, we spoke with Dr. Laura Lindsey, Ohio State Soybean Extension Specialist, and Dr. Osler Ortez, Ohio State Corn Extension Specialist, to go over crop progress at the Western Agricultural Research Station in Clark County, Ohio.

Corn Progress
Crop staging on July 17^th at the Western Agricultural Research Station shows corn at V7 through R3 state depending on the planting date:

• First planting date (March 25): milk stage (R3)
• Second planting date (April 16): blister stage (R2)
• Third planting date (May 6): silking stage (R1)
• Fourth planting date (May 24): V14 stage, 14 developed leaves
• Fifth planting date (June 17): V7 stage, 7 developed leaves.

Next - what these corn stages mean?
The V7 growth stage is identified by the 7^th leaf having an visible-open collar. At this stage, the crop is increasing in nitrogen uptake. The V14 growth stage row number has already been determined, and ear shoots have been growing since V6 and is identified by having an open leaf collar on the 14^th leaf. At V15, potential kernels per ear is established but is determined through the environmental conditions during grain fill. To consider a plant to be at R1, the ear must have one or more silks coming out of the husk. The R1 stage is the only reproductive stage that is not designated by the ear. Silk will be receptive to pollen for about 10 days. At R1 the ear is only 40 to 45% of its maximum length. R1 is the appropriate time to apply fungicides if there is disease present. At the blister stage (Figure 1), the kernel is ivory colored and the inside is a clear liquid. The embryo is growing but cannot be seen without a magnifier. This occurs about 10 to 14 days after silking begins. R2 plants have reached maximum height and vegetative dry matter, and the ear has reached its maximum length. The milk stage occurs between 18 to 22 days after R1. The moisture content of the kernels is about 80% at the beginning of R3 (Figure 2). The kernel begins to add color and become yellow but the inside is white and translucent. The silks have turned brown at this stage. Kernel abortion is still possible at R3 if carbohydrate supply is low. Growth stage details were sourced from “Corn Growth and Development”.

Soybean Progress

The soybeans, in comparison to corn, will continue to grow vegetatively even though the plant is in reproductive stages. Soybean stages at the Western station follow:

• First planting date (March 25): R4 stage (full pod)
• Second planting date (April 16): R4 stage (full pod)
• Third planting date (May 6): R3 stage (beginning pod)
• Fourth planting date (May 24): R2 stage (full flowering)
• Fifth planting date (June 17): V4 stage (four unfolded trifoliate leaves).

An interesting observation from this field is that in the March 25 planted soybeans, the lower portion of the plant has pods that are at the R5.3 growth stage (or later) with seeds developing but the top of the plant is still at R4 (Figure 3). Soybean staging is done on the top four nodes of the plant with fully developed leaves, but since the soybean continues to grow vegetatively, the plant can stay in the same stage for long periods of time. This is why our first three planting dates are in similar stages but were planted six weeks apart. There is a wide spectrum of stage in these plots, but the earlier planting dates are at about the same stage which is interesting considering the lower part of the canopy of each planting date are very different developmentally. We do not know what that means in terms of yield, but we are tracking pods in the lower canopy to evaluate the seed fill through the season.

Next - what these soybean stages mean?

The V4 growth stage is determined by having four open trifoliates. At this stage plants can recover from 100% defoliation with low risk of yield loss. The R2 growth stage has an open flower at one of the two uppermost nodes on the main stem with a fully developed leaf. Flowering usually will continue for about three to five weeks. The R3 growth stage is observed when a pod is 3/16 of an inch long at one of the four uppermost nodes on the main stem with a fully developed leaf. The plant can have developing pods, withering flowers, new open flowers, and flower buds at this stage. The R4 growth stage is observed with a pod that is ¾ inch long at one of the four uppermost nodes on the main stem with a fully developed leaf. Flowering continues on the upper node branches and peak nitrogen uptake rates happen between R4 and R5 ranging from 3-4 pounds per acre per day. Details of soybean stages were sourced from “A Visual Guide to Soybean Growth Stages”

A summary of planting dates and stages at all three research locations is presented in Table 1.