Manganese Deficiency Can Worsen with Spring N Applications on Small Grains – Part 2

Richard Taylor, Extension Agronomist; rtaylor@udel.edu and Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Last week, we discussed the possibility that either the starter fertilizer or knifed in nitrogen solution from the previous year’s corn crop might be responsible for the row-like pattern to manganese (Mn) deficiency that we had observed in barley recently fertilized with broadcast nitrogen (N). We took soil tests within the rows where barley was alive and vigorously growing (good area) and between the rows where barley plants were dead or growing very poorly (Photo 1). The soil samples have been analyzed and support our original conclusion (Table 1).

 

 

Table 1. Soil test analyses of good and bad barley areas in field showing barley surviving on 30-inch row spacing.

Barley Area Sampled

Sample Depth (inches)
0 to 4 4 to 8 8 to 12
Water pH Mn lb/A Zinc lb/A Water pH Mn lb/A Zinc lb/A Water pH Mn lb/A Zinc lb/A
Bad barley 6.1 15.1 8.5 6.6 9.0* 2.9 6.6 5.0* 1.0*
Good barley 6.2 16.3 8.7 6.3 10.8 3.2 6.5 6.3* 1.3*

*Deficient soil test level

Photo 1. Barley rows generated following renewed spring growth and nitrogen application showing effect of last year’s fertilizer (either starter band or knifed in nitrogen solution). Barley between corn rows was either severely Mn deficient or had died while barley on rows 30 inches apart grew vigorously.

Another interesting factor showed up on the soil test results. While the visual symptoms resembled traditional Mn deficiency on barley, the soil test indicated that at the deepest (8 to 12 inch) sampled layer zinc was also deficient. For any crop planted after barley (soybeans by tradition), the grower should conduct a tissue analysis mid-season before the crop begins to bloom to determine if tissue zinc levels indicate the possibility of a hidden zinc deficiency that could reduce yield potential. In addition, the grower should scout the crop for obvious zinc and Mn deficiency symptoms so that foliar zinc or Mn can be applied as early as possible.

Zinc deficiency symptoms on soybean include the following:
· Soybean yields are considerably decreased in zinc deficient soils.

  • · Deficient plants have stunted stems and leaves with chlorotic interveinal areas.
  • · Later on the entire leaves turns yellow or light green.
  • · Lower leaves may turn brown or grey and may drop early.
  • · Few flowers are formed and the pods that are formed are abnormal and slow in maturity.

Manganese deficiency symptoms on soybean include the following:
· Manganese deficiency commonly occurs in plants in well drained, neutral and alkaline soils.

  • · Interveinal areas become light green to white and the veins remain green.
  • · Necrotic brown spots develop as the deficiency becomes more severe.
  • · The leaves drop prematurely.
  • · Soybean yields can be significantly reduced by Mn deficiency.

Both micronutrient deficiencies can be reduced or eliminated by either a soil application of the sulfate or oxide compound of the micronutrient at 15 to 25 lbs per acre or by a foliar application of either the chelated form of the micronutrient or the sulfate form of the micronutrient at 1 to 2 lb of the nutrient per acre.

 

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