Efficient Management of Micronutrients in Rice K. V. Rao Principal Scientist (Soil Science) Directorate of Rice Research

Fertilizer nutrient consumption and balance in Indian Agriculture Year Fertilizer consumption (M. tons) N P2O5 K2O Total 1951 - 0.065 1999 11.6 4.8 1.7 18.1 2020 20.74 6.77 2.06 29.07 Crop uptake (M. tons) 11.87 5.27 20.32 37.46 Deficit +8.9 +1.5 -18.3 -8.3

Zone wise consumption ratio of nutrients (NPK) 2007-2008 P2O5 K2O Total (kg/ha) North 17.5 3.9 1 161.5 East 4.1 1.6 103.5 West 5.1 2.6 82.5 South 2.8 1.4 154.9 All India 5.5 2.1 117 3

Emerging Nutrient Deficiencies

Critical limits and extent of deficiency in Indian soils Nutr-ient Critical limits (ppm) Extent of def. (% samples) S 10 41 Zn 0.6 49 Fe 4.5 12 Cu 0.2 3 Mn 2.5 4.4 B 0.5 32

Deficiency of Boron in Indian soils State/soil % Deficiency Bihar 39.0 West Bengal 68.0 Karnataka 32.0 UP 24.5 MP 22.5 TN 21.0 Punjab 13.0 Gujarat 2.0 Haryana 1.5 India 33.0 Red & laterites 37-68

Deficiency of Sulfur in different states Bihar 28.0 Rajasthan 23.0 Kerala 33.0 Karnataka 34.0 HP 43.0 Orissa 51.0 UP 62.0 MP 40.0 TN 36.0 Punjab 26.0 Gujarat 38.0 Haryana 35.0 India 41.0

Soil/water resources and rice production Rice production demand by 2025 ~ 125 Mt Rice is cultivated in > 44 M. ha of variety (15) of soils; and consume > 50% of irrigation water; 38-40% of fertilizers; and 17-18% of pesticides About 8M.ha of rice soils are deficient in Zn, and is most preferred crop in salt affected soils (> 8M.ha) About 15 M ha of rice soils are acidic associated with Fe or Al toxicity, depletion of bases (Ca, K, Mg), P fixation and likely deficiency of B, Si Blanket fertilizer management over large domains Stagnation/ deceleration in productivity growth, and changing pest and disease intensity Major nutrient problems observed in rice are – Deficiency - N, P, Zn, Fe, S, K, Mn, Ca, B, Si and Toxicity - Fe, H2S, Al, B, As, Se 9

Zn deficiency in rice It is widely spread in calcareous, clayey-neutral, saline-sodic, coarse-textured, highly weathered and leached soils in Bihar, Karnataka, AP, Punjab, Haryana, UP, Tamil Nadu, orissa, Maharashtra, and Madhya Pradesh, Uneven plant growth in patches and stunted, earliness, low spike let no. and yield. Brown to dusty brown spots on younger leaves in red soils, yellowing of leaves /midrib bleaching in black soils appearing at 2–4 WAT.

ZINC MANAGEMENT Regular application of OM (FYM, PM, BG slurry, Compost) @ 5-10 t /ha helps mitigate deficiencies of all micronutrients Drain the fields frequently with good quality irrigation water Normal soils- Apply 5.5 -11.0 kg Zn /ha for every 3 seasons preferably in rabi season in soils with < 0.3-0.5 ppm Zn in sandy and clay soils, respectively Sodic soils / Brackish ground water - 22 kg Zn / ha initially followed by 5-10 kg Zn in the later years or 50% gypsum + 10 t GM + 22 kg Zn once in 2-3 years Seed treatment or root dipping in 2.0% ZnO suspension in moderate Zn deficient soils Mid season correction -Spraying 0.5% ZnSO4 thrice at weekly intervals between 3-6 WAT Grow Zn efficient and tolerant varieties- Vikas, Rasi, Hybrids etc

Response of crops to zinc fertilization in India No. of Expts. Range of response t ha-1 Av. Resp. t ha-1 Individual expt. Mean of expt. Wheat 2447 0.00-4.70 0.01-1.47 0.42 Rice 1652 0.00-5.47 0.14-1.27 0.54 Maize 280 0.01-3.09 0.11-1.37 0.47 Sorghum 83 0.07-1.35 0.21-0.65 0.36 Soybean 12 0.08-0.69 0.16-0.39 Onion 3 1.36-8.70 1.70-4.91 5.13 Potato 45 0.10-7.60 2.40-3.90 3.0 Sugarcane 6 8.00-4.30 1.72-2.40 3.8 Source: M.V. Singh (1997, 1999a), AICRP Micronutrients , IISS, Bhopal

Effect of zinc and gypsum application on yield of rice in sodic soils(t/ha) ZnSO4 (kg/ha) Gypsum levels (t/ha) Mean 2.5 5.0 10.0 0.13 0.98 2.14 2.65 1.48 10 0.49 1.87 3.06 3.77 2.30 20 0.58 2.00 3.14 3.85 2.39 30 0.68 1.75 2.99 3.92 2.34 40 1.05 2.02 3.29 3.89 2.56 0.59 1.72 2.93 3.62 - LSD (0.05) Gypsum 0.36; ZnSO4 0.28 13

Fe deficient upland rice Iron Deficiency in rice Fe deficient upland rice Interveinal chlorosis of emerging leaves, whole leaves becoming chlorotic and turns very pale. Plants become stunted with narrow leaves. Fe deficiency is serious constraint to rice in uplands in neutral, alkaline and calcareous soils, in coarse textured low organic matter soils, in alkaline and calcareous low lands, and under excessive concentrations of Mn, Cu, Zn, Al and nitrates in root zone.

Management of Fe deficiency Sources- Ferrous sulphate (19-20.5%Fe), Fe-EDTA (9-12%Fe), Fe- EDDHA (10% Fe), besides organic manures (FYM 0.15% Fe), poultry and piggery manure (0.16% Fe), sewage sludge are used as sources for correcting Fe chlorosis. Seed treatment with 2% FeSO4.7H2O solution/slurry. Foliar sprays (2-3) of 1-2% FeSO4.7H2O/FeNH4SO4 (pH 5.2) solution or of chelates at weekly interval at early stage of deficiency are successful. Combination of green manure (GM) or organic manures with foliar spray of un-neutralized 1%FeSO4.7H20 /FeNH4SO4 (pH 5.2) solution

Sulfur Nutrition in Rice Rice field showing S deficiency symptoms Chlorosis of young leaves and necrosis of tips Soils with low organic matter status, highly weathered ,containing large amounts of Fe oxides, sandy soils are deficient in S supply. About 3-5 kg S is removed by rice per ton of grain. Apply 30-40 kg/ha S through gypsum, phospho-gypsum, ammonium sulphate, elemental S etc., Reduced plant height and tillering

Boron deficiency in rice B deficiency occurs in highly weathered, acid upland, coarse textured sandy soils, acid soils derived from igneous rocks, and in soils of high organic matter and calcareousness B availability is reduced under moisture stress and dry conditions B deficiency symptoms usually appear first on young leaves. Reduced plant height and the tips of emerging leaves are white and rolled Rice plants fail to produce panicles if they are affected by B deficiency at the panicle formation stage

Management of Boron deficiency Borax, granubor & boric acid are efficient sources Basal soil application of B (1-2 Kg B / ha) is superior to foliar sprays. Soil application has residual effect for 1-2 seasons For hidden deficiency spray 0. 2% boric acid or borax at pre flowering or flower head formation stages AICRIP results show increased grain number (25-45), filled spike lets and significant increase in grain yield by 4-8% of cultures IET 20979, IET 21007 and IET 21014. Influence of Boron application on rice yield (g/sq.m) (11 locations, AICRIP, 2009)

Manganese deficiency in rice wheat system Manganese deficiency in rice is sporadic and increasing in wheat in Punjab in R-W system (after 7-10 years) in highly permeable alkaline soils low in OM Also in highly degraded, acid sulfate and acid upland soils, and alkaline / calcareous soils with low OM and reducible Mn Symptoms on rice are pale grayish green interveinal chlorosis from tip to base of young leaves with necrotic brown spots developing later. Management Soil application - MnSO4.4H2O @ 40-50 kg/ha (less economical) Foliar spray 3-4 times @ 0.5-1.0% MnSO4 solution (5-15 kg Mn /ha) at tillering stage in about 200 L water per ha. Durum wheat more susceptible than aestivum wheat. Apply farmyard manure or straw incorporation Chelates are less effective because Fe and Cu displace Mn.

Residual response (kg/ha) to secondary and micro- nutrient applied in rice under RWCS Site S Zn B Mn Cu Ranchi 48 - Modipuram 1350 960 580 600 Kanpur 511 286 R.S. Pura 191 183 57 277 Pantnagar 505 471 Ludhiana 167 90 96 36 119 Average 462 313 382 231 173 PDCSR and IPNI Research, Modipuram

Approved micronutrient fertilizers under FCO Materials Element/Forms Content (%) Zinc sulphate. Zn 21.0 Manganese Sulphate* Mn 30.5 Ammonium Molybdate Mo 52.0 Borax (For soil application) B 10.5 Solubor (Foliar spray) 19.0 Copper Sulphate* Cu 24.0 Ferrous sulfate Ferrous & Ferric 19.0 & 0.50 Zinc Sulphate mono-hydrate 33.0 Zinc Phosphate Zn3(PO4)2.4H2O Zn + P 19.5 Chelated Zn (EDTA form) 12.0 Chelated Fe (EDTA form) Fe Boronated super phosphate B+P2O5 0.18B +16.0 Zincated urea Zn+N 2.0 Zn + 43.0 N *S % in ZnSO4.7H2O-15%, MnSO4.4H2O -17%, CuSO4.5H2O-13%, FeSO4.7H2O-19%

Iron toxicity in rice Tiny brown spots from tips to leaf base of older leaves, reddish brown, purplish bronzing, yellow orange discoloration Commonly observed at maximum tillering / heading stage Reduces yields by12-100%. Reported in Orissa (42%), West Bengal, Chattisgarh, Jharkhand, Kerala, NE and NW hills, HP, Karnataka, North costal AP, in acid and acid sulfate soils rich in reducible iron, light textured, moderate to high SOM, and low CEC.

Management of Fe toxicity Plant rice tolerant varieties (e.g., Mahsuri, Phalguna, MTU 1010, IET 20550). Seed treatment (DSR) with Ca peroxide @ 50–100% seed wt. Delaying planting until peak in Fe2+ concentration has passed (> 10–20 DAF) Intermittent irrigation and midseason drainage at mid-tillering stage (25–30 DAT/DAS), Balanced use of fertilizers (NPK or NPK + lime), additional K, P, and Mg fertilizers.

Sulfide toxicity Symptoms Management S toxicity occurs in degraded, low active Fe status, poorly drained organic soils, acid- sulfate soils. Deficiency of K and unbalanced crop nutrient status, excessive application of urban or industrial sewage aggravate sulfide toxicity Symptoms Reduced nutrient uptake due to decreased root respiration Interveinal chlorosis of emerging leaves, coarse, sparse, and blackened roots, Toxicity occurs at >0.07 mg H2S per L in soil solution Management Midseason drainage at mid tillering stage (25–30 DAT/DAS), Avoiding flooding and maintain moist conditions for 7–10 days Apply K, P, lime and Mg fertilizers, and Fe (salts, oxides) to immobilize H2S . Avoid large quantities of organic matter application Dry plough field after harvest to oxidize S and Fe

Aluminium toxicity Symptoms Occurrence Orange-yellow interveinal chlorosis of younger leaves Poor growth stunted plants Yellow to white mottling of interveins, followed by leaf tip death and leaf margin scorch Necrosis of chlorotic areas occurs if Al toxicity is severe Occurrence Al toxicity is major constraint in acid upland soils of pH <5.2 with large exchangeable Al content in NEH, Jharkhand, WB, Assam, Acid sulfate soils when grown as upland crop few weeks before flooding

Al toxicity management Planting tolerant cultivars which accumulate less Al and absorb Ca and P efficiently e.g. IR43,CO37 and Basmati 370 Liming of soil with CaCO3 preferably dolomite lime to supply Mg @ 2-4 t/ha to neutralize soil acidity and replace exchangeable Al. Correct sub soil acidity by leaching soluble source of Ca like gypsum / phosphogypsum / SSP / lime Incorporate 1 t/ha of reactive rock phosphate to supply P Planting Al-tolerant cultivars such as IR43, CO 37, and Basmati 370 which complex soluble Al by root exhudates and accumulate P, Mg and Ca Soil mulching and / or green manuring / organic manuring prevents water loss and phytotoxicity

Boron toxicity Occurs in arid and semi arid regions, high in temperature, in volcanic soils Use of B-rich groundwater, sewage and municipal wastes or borax Critical toxicity limits of B in soils - > 4 mg/ kg (0.05N HCl) or > 5 mg B per kg (hot-water soluble B) or > 2 mg B per L in irrigation water. Symptoms Plants show brownish leaf tips and dark brown elliptical spots on leaves Management Deep plowing during off season and leaching, use of surface water with low B content or dilution, Growing tolerant varieties like IR42, IR46, IR48, IR54,

Management of Si deficiency Rice absorbs ~100 kg Si per ton of grain. Si-deficient plants are susceptible to lodging with soft, droopy leaves and culms, Lower leaves with yellow / brown necrotic, Critical concentration for Si - 40 mg Si per kg soil (1 M Na acetate 4.0 pH) Si deficiency occurs in old and strongly weathered, leached acid soils, and due to removal of rice straw , excessive use of N. Si deficiency is not yet common in intensive irrigated rice systems of tropical Asia. Management of Si deficiency Recycling rice straw (5–6% Si), and rice husks (10%), applying rice hull ash and balanced nutrient use of NPK Apply granular silicate fertilizers for rapid correction- Ca silicate: 120–200 kg/ha; K silicate: 40–60 kg/ha Apply basic slag @2-3 t/ha once in two years, or fly ash (23% Si) use is beneficial Foliar spray Si @0.1-0.2% with sodium silicate improve Si nutrition

Efficient genotypes for nutrient stress situation Low N Swarna, Sarjoo-52, Bejhary, Pranava, Salivahana Low P Rasi, RPA 5929, MTU 2400, Vikramarya Low Zn CSR 10, Sarjoo-52, Vikas, IR-30864 Fe toxicity Mahsuri, Phalguna, Dhanrasi

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Low nutrient use efficiency in rice 30-40 P 15-20 K 40-50 Zn 2-5 Fe 1-2 S 20-25

Distribution of Sulphur Deficiency (240 Districts) A- 45% Districts having > 40% soil samples deficient in S B- 40% Districts having 20-40% soil samples deficient in S C- 15% Districts having < 20% soil samples deficient in S

AVAILABILITY INDICES FOR MICRONUTRIENTS Critical level (ppm) Range Mean B Hot water soluble 0.1-2.0 0.7 Cu Mehilch No.1 DTPA + CaCl2 (pH 7.3) AB-DTPA (pH 7.6) 0.1-10 0.12-2.5 3.0 0.8 1.8 Fe 2.4-5.0 4.0 Mn 0.03 M H3PO4 4-8 1.0-2.0 0-20 7.0 1.4 10 Mo (NH4)2C2O4 (pH 3.3) 0.04-0.2 - Zn 0.1N HCl Mehlich No.1 2.0-10.0 0.5-3.0 0.25-2.0 5 1.1 1.5

Major management-related concerns in Agricultural Production Increasing food demand >300 Mt. by 2025; Rice - >130 Mt Low and imbalanced use of fertilizers and OM -negative balance, soil nutrient depletion, low NUE and declining soil quality Blanket fertilizer management over large domains Increasing area under water and management induced soil degradation Stagnation/ deceleration in productivity growth in intensive rice crop systems Changing pest and disease intensity and scenario Nt related