News Story

GDU's and Growth Stages, Nitrate and Tissue Sampling, Nitrogen levels in the soil

Brian Weller, Lead Agronomist

As warm, and as dry as it has been, I have washed vehicle’s the last few days, left windows open, and have asked people to cut hay, all in the name of tempting Mother Nature to give us a slow, gentle, all day or all night rain. Moisture would cure many of the ills that we are presently seeing in our fields, both corn and soybean.

 

In reviewing Nitrate levels from our NitrateNow program, Nitrate levels have been coming in consistently lower than what we have normally seen, and expected through the years. What is unusually concerning, these Nitrate levels are in the single digits whereas we normally see them in the teens or low twenty’s. These very low Nitrate levels are coming in on almost all fields.

 

Fields that are especially concerning are ones that are relying solely on a manure application for the crops total season nutrient needs. These fields in most cases are alarmingly low in Nitrate levels.

 

Other fields that I am concerned about are ones that have higher levels of compaction or sidewall compaction. Plants/fields that have limited root growth, will not be able to capture enough of the Nitrogen soon enough, and because of the compromised root growth, the ability to capture and utilize the soils “natural” late season nitrogen will be inadequate and yield limiting. The old adage “don’t guess soil test” rings especially true with Nitrogen Management this year.

 

In the last few years I have utilized tissue sampling more and more to help with in season nutrient management, so much so, that it seems they have almost become a “report card” for nutrient availability, to actively growing plants. Much like Nitrate samples or grid soil samples, tissue samples help measure where nutrient levels are on your fields or parts of fields. Recently, I was reminded of the saying “if you measure something you have a better chance of managing it”, tissue samples are the poster child for this phrase. Tissue sampling normally starts around the V5 (fifth leaf or collar) growth stage, and I encourage producers to pull samples from their fields to start finding out where our in season nutrient levels and needs are at.

 

With the warmer temperatures that we have received this week we have accumulated Growing Degree Units (GDU’s) at a brisk pace.

 

Date

GDU 2017

30 year GDU

3-Jun

27

13

4-Jun

22

16

5-Jun

18

15

6-Jun

16

18

7-Jun

19

17

8-Jun

20

17

9-Jun

22

15

Average/Day

20.57

15.86

 

This brisk accumulation of GDU’s has pushed the plant to almost put on two leaves of growth.

 

Planting Date

GDU'S

Growth Stage

12-Apr

505

V6

24-Apr

450

V5

5-May

421

V4-V5

12-May

366

V4

2-Jun

164

V1

 

As a corn plant reaches V6 the amount of GDU it takes to put on a new leaf/collar or growth stage reduces 65-70 GDU’s.

 

Growth Stage

GDU's

Emergence to V6

85-90

V6 to V14

65-70

 

At the present rate of GDU accumulation new collars could be adding a little over 3 days/collar, where a “normal” rate would be about 4 days/collar. To quote a popular comedic scholar “That’s Quuuuuick”.