The following points highlight the twelve major types of nutritional disorders in rice. The types are: 1. Nitrogen 2. Phosphorus 3. Potassium 4. Calcium 5. Magnesium 6. Sulphur 7. Iron 8. Manganese 9. Zinc 10. Boron 11. Copper 12. Silicon.
Nutritional Disorder: Type # 1. Nitrogen (N):
Stunted plants with limited number of tillers; narrow and short leaves, which are erect; lower leaves become yellowish green, while young leaves remain green; and old leaves become light-straw coloured and entire field may appear yellowish. Leaves die under severe N stress.
Common in all rice-growing soils and occurs at critical growth stages such as tillering and panicle initiation.
Nutritional Disorder: Type # 2. Phosphorus (P):
Stunted plants with thin stem and limited number of tillers; narrow and short leaves that are erect and dirty dark green; and young leaves remain healthier than older leaves, which turn brown and die; some varieties (having a tendency to produce anthocyanin) have reddish or purple colour at the base of leaves.
The number of leaves, panicles, and grains per panicle is also reduced. Leaves appear pale green when P and N deficiency occur simultaneously. Occurs in coarse textured, acid upland soils where soil P-fixation capacity is often large. Deficiency is often associated with other nutrient disorders such as Fe toxicity at low pH, Zn deficiency, Fe deficiency, and salinity in alkaline soils.
Nutritional Disorder: Type # 3. Potassium (K):
Stunted plants, and tillering slightly reduced; short and droopy plants with dark green leaves; yellowing at the interveins of lower leaves, starting from the tip and eventually drying to a light brown colour; brown spots sometimes develop on younger dark green leaves; irregular necrotic spots may develop on the panicles; long and thin panicles form; and symptoms of wilting when low K: N ratio in plants.
General pattern of damage is patchy within a field, affecting single hills rather than the whole field and greater incidence of lodging; Increased incidence of diseases, particularly brown leaf spot (caused by Helminthosporium oryzae), cercospora leaf spot (caused by Cercospora spp.), bacterial leaf blight (caused by Xanthomonas oryzae), sheath blight (caused by Rhizoctonia solani), sheath rot (caused by Sarocladium oryzae), stem rot (caused by Helminthosporium sigmoideum), and blast (caused by Pyricularia oryzae) where excessive N fertilizer and insufficient K fertilizer have been used.
Occur in coarse-textured soils, highly weathered acid soils, acid upland soils, lowland clay soils, soils with a large K content but very wide, leached, “old” acid sulfate soils, poorly drained and strongly reducing soils, and organic soils.
Nutritional Disorder: Type # 4. Calcium (Ca):
Causes little change in general appearance of the plant, except in case of acute deficiency; the tips of the upper growing leaves become white, rolled, and curled; necrosis along the lateral margins of leaves; the plant is stunted and growing points dies; old leaves turn brown and die.
Common in acid, strongly leached, low-CEC soils in uplands and lowlands, soils derived from, serpentine rocks, coarse-textured sandy soils with high percolation rates and leaching, and leached, old acid sulfate soils with low base content.
Nutritional Disorder: Type # 5. Magnesium (Mg):
With moderate deficiency, height and tiller number are little affected. Intervienal chlorosis characterized by an orangish-yellow colour first on lower leaves; green coloring appears as a “string of beads” in which green and yellow stripes run parallel to the leaf.
Leaf number and leaf length are greater in Mg-deficient plants and leaves look wavy and droopy due to expansion of the angle between the leaf blade and the leaf sheath. In severe cases, chlorosis progresses to yellowing and finally necrosis in older leaves.
Reduced number of spikelets and reduced 1,000-grain weight; may reduce grain quality (% milled rice, protein, and starch content). Fe toxicity may be more pronounced where Mg is part of multiple nutrient deficiency stress involving K, P, Ca, and Mg.
More common in rainfed lowland and upland rice; may also be induced by large applications of K fertilizer on low Mg status soils.
Nutritional Disorder: Type # 6. Sulphur (S):
Similar to nitrogen deficiency; in case of nitrogen lower leaves look yellow, whereas in case of sulphur, the upper leaves look yellow; first leaf sheath look yellow and then the yellowing proceeds to leaf blade; high seedling mortality after transplanting; at maximum tillering the whole plant looks chlorotic; plant height, tiller number and spikelet number reduced; number and length of auricles reduced; and delay in maturity by 1 -2 weeks. S-deficient rice plants have less resistance to adverse conditions (e.g., cold).
Common in soils containing allophane, soils with low organic matter status, highly weathered soils containing large amounts of Fe oxides, and sandy soils
Nutritional Disorder: Type # 7. Iron (Fe):
Development of a pronounced intervienal chlorosis similar to that caused by Mg- deficiency; symptoms occur first on the youngest leaves. Intervienal chlorosis is some times followed by chlorosis of veins, so the whole leaf then becomes yellow. In severe cases, the young leaves even become white with necrotic lesions and plant may die.
Mainly a problem in upland soils and can also be a source of yield loss in alkaline or calcareous soils
Nutritional Disorder: Type # 8. Manganese (Mn):
Stunted plants with normal tillers and fewer leaves and smaller root system at tillering; interveinal chlorosis on the leaves spread from the tip to the leaf base; necrotic brown spots develop later and leaf becomes dark brown> newly emerging leaves short, narrow, and light green.
Affected plants more susceptible to brown spot (caused by Helminthosporium oryzae). Mn-deficient rice plants often deficient in P. In soils where both Mn deficiency and Fe toxicity occur, Mn-deficient rice plants contain a large concentration of Fe, and may also show symptoms of bronzing.
Common problem of acid upland soils, alkaline and calcareous soils, degraded paddy soils, leached sandy soils, old acid sulfate soils and highly weathered soils.
Nutritional Disorder: Type # 9. Zinc (Zn):
Symptoms appear between two to four weeks after transplanting. Stunted and uneven plant growth with reduced size of the leaf blade; the midribs of the younger leaves (especially the base) become chlorotic; brown blotches and streaks on lower leaves; delayed maturity; and increase spikelet sterility. Symptoms may be more pronounced during early growth stages because of Zn immobilization.
Occurs in neutral and calcareous soils, intensively cropped soils, very poorly drained soils, sodic and saline soils, peat soils, soils with high available P and Si status, sandy soils, highly weathered, soils derived from serpentine and laterite, and leached, old acid sulfate soils with a small concentration of K, Mg, and Ca associated with S deficiency.
Nutritional Disorder: Type # 10. Boron (B):
Reduced plant height, the tips of emerging leaves become white and rolled as in the case of calcium deficiency; and the growing points may die in severe cases but new tillers continue to be produced.
The soils on which B deficiency occurs include those which are inherently low in B such as soils derived from acid igneous rocks and podzolised soils. Heavy leaching soils and calcareous soils are generally deficient in boron.
Nutritional Disorder: Type # 11. Copper (Cu):
Bluish-green leaves, which become chlorotic near the tips, development of chlorosis downward along both side of the midrib, followed by dark brown necrosis of the tips and new leaves fail to unroll and look needle like. Low tillering with reduced pollen viability which increase spikelet sterility with many unfilled grains.
More common in high organic matter status soils, lateritic, highly weathered soils, soils derived from marine sediments, sandy textured soils, and calcareous soils
Nutritional Disorder: Type # 12. Silicon (Si):
Plants become soft and droopy thus increasing mutual shading; lower/reduced grain yields; plants are particularly susceptible to lodging. Increased occurrence of diseases such as blast (caused by Pyricularia oryzae) or brown spot (caused by Helrninthosporium oryzae). Severe Si deficiency reduces the number of panicles m2 and , the number of filled spikelets per panicle
Common in old and degraded paddy soils, organic soils with small mineral Si reserves, and in highly weathered and leached tropical soils in the rainfed lowland and upland areas.