In this Brassica carinata (Ethiopian mustard) research update, we highlight the symptoms of sulfur deficiency. These images are part of a project by the Southeast Partnership for Advanced Renewables from Carinata (SPARC) to develop a diagnostic series for the identification of nutrient disorders of Carinata. Carinata is an exciting new crop in the Southeast used for a wide variety of primary and secondary agricultural products including cover crops, feedstock, high protein meal, and jet fuel. It is similar in management to canola given both canola and carinata are winter annual Brassica oilseed crops. However, carinata oil is not edible.

Carinata, like many brassicas, require relatively large amounts of sulfur (S). As a result of their higher sulfur demand, carinata will manifest sulfur stress rapidly. Sulfur is a structural element of two essential amino acids, cysteine and methionine. Lack of these amino acids results in insufficient protein synthesis, resulting in chlorosis similar to that of nitrogen in many ways.

Sulfur (S) deficiency in carinata will first manifest as a slight yellowing or paling of the middle foliage and will rapidly spread over the entire plant (Figure 1). Both S and nitrogen deficiencies manifest as chlorosis of the foliage. The key distinguishing characteristic between the two in carinata is the location of the symptoms. Nitrogen deficiency will begin as a yellowing of the lower foliage, while S deficiency will manifest as an overall yellowing that may be slightly more apparent on the middle foliage (Figure 2A and Figure 2B).

Sulfur deficiency progression manifests as a folding of the foliage. It is important to note that sulfur, unlike calcium or potassium, deficiency does not curl the leaf margin but rather folds the leaf along the midrib giving the leaves a wilted, rather than distorted, look (Figure 3A, Figure 3B, and Figure 3C). The leaf margin will also fold, resulting in a wavy margin rather than a curled or distorted margin.

In advanced S deficiency, carinata will exhibit a red to purple coloration of the entire underside of the leaves (Figure 4A and Figure 4B). These leaves will eventually become completely necrotic and abscise. To ensure proper diagnosis the above material should be used in conjunction with a leaf tissue sample and / or soil test. To ensure proper diagnosis the above material should be used in conjunction with a leaf tissue sample and/or field test.

Figure 1. The initial symptoms of sulfur deficiency in carinata begin as an overall paling of the leaves. This paling is often seen more severely in the mid foliage.

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Figure 1. The initial symptoms of sulfur deficiency in carinata begin as an overall paling of the leaves. This paling is often seen more severely in the mid foliage.

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Figure 2A. Both nitrogen deficiency (this photo) and sulfur deficiency (Figure 2B) will manifest as yellowing of the foliage. Note in this photo, the yellowing due to nitrogen deficiency is in the lower foliage.

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Figure 2A. Both nitrogen deficiency (this photo) and sulfur deficiency (Figure 2B) will manifest as yellowing of the foliage. Note in this photo, the yellowing due to nitrogen deficiency is in the lower foliage.

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Figure 2B. Note in this figure the yellowing or paling due to sulfur deficiency is over the entire surface of the plant.

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Figure 2B. Note in this figure the yellowing or paling due to sulfur deficiency is over the entire surface of the plant.

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Figure 3A. Sulfur deficiency will result in distorted or altered growth of carinata leaves. Note that in sulfur deficiency, the foliage will often fold along the midrib.

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Figure 3A. Sulfur deficiency will result in distorted or altered growth of carinata leaves. Note that in sulfur deficiency, the foliage will often fold along the midrib.

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Figure 3B. Calcium deficiency can result in distorted growth. However, in calcium deficiency the newest foliage of the plant will distort, showing cupping and marginal distortion resulting in a hood-like structure.

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Figure 3B. Calcium deficiency can result in distorted growth. However, in calcium deficiency the newest foliage of the plant will distort, showing cupping and marginal distortion resulting in a hood-like structure.

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Figure 3C. Potassium deficiency can result in distorted growth. However, in potassium deficiency leaves will distort severely and wrinkle or even fold backwards on themselves. Potassium will also be accompanied with necrotic regions of the leaf margin.

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Figure 3C. Potassium deficiency can result in distorted growth. However, in potassium deficiency leaves will distort severely and wrinkle or even fold backwards on themselves. Potassium will also be accompanied with necrotic regions of the leaf margin.

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Figure 4A. Advanced sulfur deficiency symptoms, much like magnesium deficiency, will result in a purpling or reddening of the underside of the leaf. Note the uppermost leaf has a reddish tint to the underside of the leaf.

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Figure 4A. Advanced sulfur deficiency symptoms, much like magnesium deficiency, will result in a purpling or reddening of the underside of the leaf. Note the uppermost leaf has a reddish tint to the underside of the leaf.

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Figure 4B. The uniform reddening or purpling of sulfur deficiency can be seen more clearly. However, a magnesium deficiency exhibits purpling or reddening in the interveinal regions of the leaves.

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Figure 4B. The uniform reddening or purpling of sulfur deficiency can be seen more clearly. However, a magnesium deficiency exhibits purpling or reddening in the interveinal regions of the leaves.

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