Visual Symptoms of Nutrient Deficiency in Axonopus compressus (Cow Grass)

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Research Technical Note
Urban Greenery Series RTN
14-2013
December
Visual Symptoms of Nutrient Deciency in
Axonopus compressus (Cow Grass)
Author: Chin Siew Wai
Introduction
Turfgrass nutrition plays an important role in maintaining the vigour and density of a lawn. Nutri-
ents are essential to support proper plant growth and development. When available in adequate
amounts, they enable plants to better adapt to environmental stress, tolerate human trac im-
pacts as well as combat invasion by weeds. Macronutrients such as nitrogen (N), phosphorous (P)
and potassium (K) are required in large amounts by plants for the formation of new roots, shoots,
expansion of leaf tissues and chlorophyll pigment synthesis while micronutrients like iron (Fe) is
closely involved in the synthesis of chlorophyll pigments.
Plants obtain nutrients from the soil substrate. Nutrients may be lost when soil leaches or when
plant tissues are removed during mowing operation. In addition, nutrients in the soil may also
be converted to forms that are unavailable for plant uptake under suboptimal soil conditions.
Therefore, it is important to apply fertilizers to replace the nutrients lost after several regular
mowing regimes or ameliorate the soil conditions to make nutrients available.
Visible symptoms of nutrient deciency are usually expressed only when nutrient levels within
the plant tissues fall below minimum critical levels that aects growth. It is useful to be able to
recognize early symptoms of nutrient deciency and apply corrective measures. This helps to
prevent the lawn quality from degrading.
This Research Technical Note (RTN) documents the early visual symptoms of nutrient deciencies
(N, P, K and Fe) in Cow Grass (Axonopus compressus) under controlled nutrient deciency condi-
tions. Coupled with experience and knowledge of the site conditions, this RTN can serve as a
diagnostic guide for operational managers.
Fig. 1 Cow Grass (A xonopus com-
pressus) lawn with complete nutri-
tion is green and dense

Visual Symptoms of Nutrient Deciency in Axonopus compressus (Cow Grass) RTN 14-2013
Nutrient deciency symptoms in Cow Grass
Nitrogen deciency symptoms
The mature leaves rst became yellowish-green with
reddish-purple streaks spreading from bases of leaves
towards the tips [Figs. 2A & B ‘N2’]. The mature leaves
turned entirely reddish-purple [Figs. 2B ‘Red’ & 2C], be-
came necrotic and caused the leaf to wither and die
(Figs. 2B & C).
When deciency persisted, young leaves too became
yellowish-green (Fig. 2B ‘N1’). The shoot density re-
duced; the lawn thinned out and weeds started to es-
tablish (Figs. 2C, D & E)
Fig. 2A
Fig. 2D
Fig. 2B
N1
N2
Red
Fig. 2C
Fig. 2E

Visual Symptoms of Nutrient Deciency in Axonopus compressus (Cow Grass) RTN 14-2013
Phosphorous deciency symptoms
Potassium deciency symptoms
Both mature and young leaves rst became uniformly
dark green (‘Phosphorous’ in Fig. 3A). The mature leaves
then turned dark purple with the pigment spreading
from the tip towards the base (Fig. 3B). The leaf tips of
the dark purple leaves became necrotic. Necrosis soon
spreads from leaf tip; causing the leaf to wither and die.
The phosphorous deciency symptoms diered from ni-
trogen deciency symptoms in which the mature leaves
rst became yellowish-green before the accumulation of
reddish-purple pigments that spread from leaf base to
leaf tip (‘Nitrogen’ in Fig. 3A & Figs. 2A, B & C)
The mature leaves rst became greenish-yellow. Ne-
crosis was observed as either small dark-brown spots
distributed randomly throughout the entire leaf (Fig.
4A) or as necrotic areas on the leaf margin (Fig. 4B) or at
the leaf tip (Fig. 4C). Necrosis soon spreads towards the
leaf base, causing the leaf to wither and die. Some of
the mature leaves wilted, mimicking a drought-stressed
condition.
Fig. 3A
Nitrogen Phosphorous
Fig. 3B
Fig. 4A Fig. 4B
Fig. 4C

Visual Symptoms of Nutrient Deciency in Axonopus compressus (Cow Grass) RTN 14-2013
Iron deciency symptoms
Applications and Limitations
• Nutrient deciency symptoms described in this RTN for Cow Grass could be used as a guide
to diagnose deciency conditions. For example, the distinct early symptoms of N and Fe de-
ciencies can be used with certainty as diagnostic tool to detect nitrogen and iron nutri-
ent deciency problem. However, it has its limitations when used to detect early deciency
symptoms of phosphorous and potassium, as symptoms are subtle and less discernible.
• One must consider the complex interactions between nutrient availability and soil pH, avail-
able soil moisture, soil oxygen levels, excesses of other nutrients, and organic matters when
interpreting the visual symptoms in order to accurately rectify the problem. Examples of such
interactions include (1) alkaline soil pH (pH > 7.0) resulting in iron to exist in insoluble Fe (III)
form that is unavailable to the plant and (2) waterlogged wet soil condition resulting in high
bicarbonate content, which restricts root uptake of iron. Therefore, accurate diagnosis of a
nutrient deciency condition cannot be based on visual symptoms alone and must be ac-
companied with soil or tissue nutrient testing.
• Routine fertilization regime with complete fertilizers, preferably 4:1:2 (N: P: K), is a positive
approach to prevent the onset of nutrient deciencies and ensure the vigorous and healthy
growth of Cow Grass plants. Conversely, if other interacting factors such as suboptimal soil
pH (too acidic or alkaline soil) or poor soil aeration (waterlogged condition) are not remedi-
ated, correction of nutrient deciencies by supplying the associated nutrients may not be
eective.
The young leaves rst displayed interveinal chlorotic
condition which made the leaves appeared ‘netted’ (Fig.
5A). The ‘netted’ leaves turned pale green to whitish-yel-
low (Figs. 5B & C); drooped while the rest of the mature
green leaves remained upright.
As deciency persisted, the mature leaves developed
similar symptoms and became necrotic at the tip; caus-
ing the leaf to wither and die.
Fig. 5A Fig. 5B
Fig. 5C