Station Circular 387
Boron Deficiency in Indiana Soils
S. A. Barber
DEPARTMENT Of AGRONOMY
March, 1953
Boron is one of six minor elements which are required for plant growth. It is required in small amounts, and most soils have an adequate supply. However, some Indiana soils do not always have enough available boron for optimum growth of alfalfa, a crop which requires a large amount of boron. These potentially deficient soils have been determined from surveys. These boron-deficient soils have been successfully corrected with applications of borax.
Alfalfa the Only Indiana Field Crop Known to be Limited by Boron
The need for soil boron depends on the plant requirements. Corn and grain crops with a boron content of less than 5 p.p.m, (parts per million) have a low requirement. They are able to obtain enough boron even on soils having a low available boron supply. Alfalfa with a boron content of around 40 p.p.m, has a high boron requirement. It is a crop which most frequently is unable to obtain enough from a soil low in boron. Some of the clovers also may show deficiency symptoms, but alfalfa is the only Indiana field crop that is frequently injured by boron starvation.
How to Recognize Boron Deficiency Symptoms on Alfalfa
A deficiency of boron in alfalfa causes the upper leaves to turn yellow and also often stunts the plant. Because of this, boron deficiency is frequently called “yellow-top.” Recognition of this deficiency is difficult, as a number of other factors also cause yellowing of alfalfa. There is a difference between the symptoms which are shown by each disorder; however, if we are able to recognize the symptoms of the different factors, we can determine with more certainty
Figure 1. Alfalfa plant is boron deficient.
Avhether or not boron deficiency is one of those causing the damage.
The symptoms associated with boron deficiency as they occur in the field are shown in Figures 1 and 2. They are:
1.	Yellowing occurs most severely on the top leaves and progresses down the plant as the severity of the deficiency increases. Sometimes the leaves turn red or brown instead of yellow.
2.	The yellowing occurs first on the tip half of the leaflet. As the damage becomes more severe, the tip dies and turns brown.
3.	The flowers die, turn brown and fail to produce seed.
4.	The plant often is stunted so that the internodes are very close together.
These boron deficiency symptoms occur most frequently during periods of drought. They will occur first in spots over the field.
Other troubles which cause yellowing or stunting of alfalfa and which may be confused with boron deficiency are:
Potasium deficiency. The leaflet turns yellow in a crescent shape about the tip of the leaflet. As the intensity of the deficiency increases, the tip dies and turns gray. The symptoms occur on both upper and lower leaves, differing from boron in this respect.
Leafhopper damage. The leafhopper attacks the midrib of the leaflet, usually about halfway to the tip. The tip turns yellow, giving a distinctive V-shape with the base of the V at the point of attack. The area inside the V and extending to the tip turns yellow. The yellow leaves may be on any part of the plant. However, they are generally concentrated on the younger tissue at the top of the plant.
Figure 2. The green strips are where borax has been applied.
Higher crop yields from improved  soils