Keys to Diagnosing Common Nutrient Deficiencies in Rice

Described below are the most common nutrient related issues that occur in Mississippi rice production and a few distinctive characteristics to key on when trying to properly identify each issue in the field.  Nutrient issues in rice can take on many appearances, but coupled with field histories some of the keys below will aid in identification.  When in doubt a tissue sample representing the good and bad areas of the field will aid in making the proper diagnosis.

Nitrogen

In mechanized U.S. rice culture most soils lack enough native N to produce obtainable maximum rice yields.  Nitrogen addition most commonly in the form of an ammonium or ammonium forming fertilizer makes up the largest portion of the N supply to the rice plant.  If properly managed, utilization and uptake efficiency of N by rice is great and can be as large as 75% of the total N applied. However, if N is mismanaged a N deficiency can occur.  Common characteristics of N deficient rice are a general stunting of the plant, an overall yellowing in appearance and in many instances older leaf tissue and/or the whole plant will appear yellowish green. Nitrogen deficiency often occurs during high N demand growth stages such as tillering and panicle initiation.

Note the difference in greeness shortly after flooding on N deficient plants

Note the lack of fullness, pale green color and lower height in N deficient plants

Phosphorus

Phosphorus is taken up by the rice plant early in the production season with peak P demand occurring around mid-tillering.  Phosphorus is essential in rice culture and helps promote rapid tillering, root development, and early flowering.  Rice plants that are deficient in P often are stunted and appear very dark green to almost bluish in color.  The most distinctive characteristic of P deficient rice is erect spindly leaves with minimal tillers on the plant. Younger tissue may appear healthy while older tissue can turn brown and become necrotic in severe cases.  Be mindful of P deficiency on fresh cut ground and or soil with low soil test P.

Note the erect spindly leaves and reduced tillering capacity. Photo credit: Chuck Wilson

Potassium

Potassium is essential to many plant functions and provides strength to cell walls in rice plants.  In contrast to phosphorus, K deficiency does not influence rice tillering.  In recent years K has become likened to a plant health food as adequate K in rice tissue helps improve the plants tolerance to many pest pressures as well as reduces the occurrences of lodging.  Potash deficient rice can take on many appearances. Because K is mobile in the plant symptoms often appear on older tissue first with K deficient plants producing yellowish brown leaf areas around the margin of leaf tissue.  K deficient tissue is often accompanied by dark brown necrotic spots, and in severe cases can cause leaf tips to turn yellow-brown eventually “drying up” and becoming necrotic. In many cases the field may have a slightly red cast across the leaf tip that almost mimics herbicide injury.

Note the yellowing around the leaf margins

Field shot of late season potash deficiency. Note the yellow to reddish brown hue across the field

Zinc

Zinc deficiency is rare in Mississippi, due to the abundance of our rice production occurring on heavy clay soils but does occur on our silt and sandy loam rice acreage.  Zinc deficiency is more prone to occur when soil pH is elevated.  Because our irrigation water generally contains an abundance of bicarbonates, alleviating  Zn deficiency requires treatment with a suitable Zn source.  Zinc deficiency in rice tends to appear after the onset of the permanent flood, and can sometimes occur after a prolonged flushing.  Common characteristics of Zn deficient rice are bronzed tissue on the older leaves that may appear splotchy, a pale green midrib, stacking of the nodes, and an overall loss of plant turgidity.  Zinc deficient rice, like corn, can produce a basal chlorosis; however, leaf tissues will appear a paler shade of green, in comparison to the bleached tissue look that corn often produces.

Note the stained “bronzing” and pale yellow mid rib. Photo Credit: Nathan Slaton

Note the Basal Chlorosis and Bronzing