DEPARTMENT OF AGRICULTURAL CHEMISTRY AND SOIL SCIENCEFACULTY OF AGRICULTURE

Bidhan Chandra Krishi Viswavidyalaya

Speaker : Sudeshna Mondal and

Dr. P. K. Mani

EFFECT OF PHOSPHORUS BUILD-UP ON THE AVAILABILITY OF ZINC IN SOILS IN A RICE

BASED CROPPING SYSTEM

Rice is one of the most important food crops and a primary food source for more than one third of world’s population (Prasad et al., 2010).In Asia, India has the largest area under rice cultivation (44.3 million ha) accounting for 29.4 per cent of the global rice area.Rice based cropping system provide the income and employment generation to 50 million household of the country.

Rice

In India, West Bengal is one of the leading states for rice cultivation covering about 4.94 million ha (Economic review, 2011-12).

The soils of West Bengal are poor in micronutrients due to continuous growing of high yielding varieties and only incorporation of macronutrients in cropping system

In West Bengal about 26% of the cultivated area is low in Zn (Hazra et al., 2012);

Zinc deficiency is widespread throughout the world particularly in lowland rice fields;

50% of cultivated soils in India are low in plant available Zn (Singh, 2009);

Zn deficiency is the fifth most important risk factor of human disorders (WHO, 2002).

Soil Factors Associated with Zn Deficiency

Soil pH

Parent material of soils and

Zn content

Soil temperatur

e

Soil texture

Soil flooding

Phosphate fertilizers

Soil organic matter

Soil Factors Associated

with Zn Deficiency

Role of Zinc in plantsDiverse enzymatic activityProtein synthesisStructural and functional integrity of cell

membranesDetoxification of reactive oxygen species

(ROS)Carbohydrate metabolismSynthesis and production of IAAReduces heavy metal accumulation

Zinc in plantsZn is absorbed by plant roots as Zn2+.

Zn concentration in plants ranges between 25 to 150 ppm. Zn deficiencies are usually associated with concentrations of <10-20 ppm, depending on the crop.

Common deficiency symptoms of Zn include:

Light green, yellow, or white areas between leaf veins, particularly in younger leaves

Eventual tissue necrosis in chlorotic leaf area

Shortened internodes (rossetting), resulting in stunted or bushy plants and decreased leaf expansion (little leaf)

Premature foliage loss

Malformation of fruit, often with little or no yield.

Deficiency symptoms of Zn in rice

Source: Dobermann and Fairhurst, 2000

Role of Phosphorus in plants Energy storage and transfer Photosynthesis Transformation of sugars and starches Increases water use efficiency and thus

reduces water stress Helps in seed formation Promotes early root formation and growth Early crop maturity Transfer of genetic characteristics

Phosphorus in plants

Common deficiency symptoms of P:Because of faster mobility of P in plants, deficiency symptoms appears first on the older leaves.

Production of dark green color leaves.

Severe restriction occurs in the growth of plant tops and roots.

Plants become thin, erect and spindly with sparse and restricted foliage.

Foliage turns bluish-green due to increasing deficiency.

P absorbed by plant roots as H2PO4-1 or HPO4

-2.P concentration in plants ranges between 0.1 to 0.4 %. P

deficiencies are usually associated with concentrations of <0.1%.

To study the effect of P-Zn interaction in agricultural crops

To study the mechanism of this interaction

Management practices to overcome the effects

OBJECTIVES

How does P build up in soil occurs?

Phosphorus added to most soils so that there are adequate levels for optimum crop growth and yield

P is rapidly fixed in relatively insoluble forms and thus become unavailable to plants, depending on soil pH and type (Al, Fe and Ca

content)

Conversion of stable forms of soil P to available occurs too slowly to meet crop P requirements

Continual long-term application of fertilizer or manure at levels exceeding crop needs increases soil P levels

Trends in Olsen P in two F-W-W rotation, one receiving no P and the other receiving 6.5 kg P ha-1 yr-1

Increase in soil test P from applying more P than a crop needs each year (as Bray-I P). A negative surplus indicates crop and soil removal.

Phosphorus build up in soil

Source: Zentner et al., 1993 Source: Barber, 1979

Effect of long term phosphorus application in soil

Treatments Available P (kg ha-1)

Total P (kg ha-1)

Fallow 32.30 1015

Control 26.88 874

100% recommended dose of N 22.35 780

100% recommended dose of N and P 52.04 965

100% recommended dose of N, P and K 63.37 1098

100% recommended dose of NPK + compost 117.42 1469

Mean 52.39 1033

Source: Chakraborty, 2007

P AND ZN INTERACTIONPhosphorus is the most important

element which interferes on zinc uptake by plants.

High levels of available P or the heavy application of P to the soil induced Zn deficiency in plants grown in soil low in available Zn (Olsen, 1972).

This P and Zn interaction is also known as P-induced Zn deficiency.

Causes of P and Zn interactionA simple dilution effect on the concentration of Zn in plant tops due to growth response to P

A slower rate of translocation of Zn from the roots to tops

Difference in the distribution of zinc between roots and tops as Zn is less mobile in plant

Physiological effects like phosphorus interference in the utilization of zinc by plant

Precipitation of zinc by phosphorus in the veins and conductive tissues

Root/shoot Zn uptake ratio in sweet corn plants in nutrient solution with different P and Zn levels

Treatment (mg L-1) Root/shoot Zn uptake ratioZn P 7 DAT 14 DAT0 0 0.84 0.62

20 0.28 0.7240 0.44 0.7880 0.36 1.84

5 0 0.68 0.7820 0.98 0.9840 1.16 2.5280 2.08 1.36

10 0 0.90 1.9020 1.44 1.9040 2.54 1.6280 1.74 1.10

20 0 1.34 1.1020 1.82 3.0440 2.86 2.4080 2.56 3.42

Source: Soltangheisi et al., 2013

Effect of P and Zn on Zn concentration (ppm) in shoots and roots of rice

Treatment

Shoot Root

Zn0 Zn5 Zn10 Mean Zn0 Zn5 Zn10 Mean

P036.0 41.5 45.

5 41.0 50.3 58.2 62.3 56.9

P2535.2 38.6 42.

3 38.7 49.8 55.0 59.3 54.7

P5030.2 33.3 37.

8 33.7 44.4 48.0 52.8 48.4

P10026.4 28.4 32.

1 29.0 40.9 42.3 45.5 42.9

Mean 31.9 35.4 39.

446.3 50.9 55.0

Source: Mandal and Mandal, 1990

Effect of P and Zn application on the uptake of Zn by shoots and roots of rice

Treatment

Shoot (µg/pot) Root (µg/pot)

Zn0 Zn5 Zn10Mean Zn0 Zn5 Zn10

Mean

P0230 296 343 289 116 156 180 150

P25231 290 335 285 129 173 196 166

P50221 283 336 280 128 164 183 158

P100199 266 317 260 138 162 175 158

Mean 220 283 332 127 163 183

Source: Mandal and Mandal, 1990

Effect of P application on the ratio of the Zn concentration in rice root and shoot

Source: Mandal and Mandal, 1990

Effect of P and Zn application and their interaction on grain P and Zn uptake of wheat

Treatment

P uptake (kg/ha) Zn uptake (g/ha)

P0 P30 P60 P90 P0 P30 P60 P90

Zn010.24

18.28

22.70

31.71

178.03

184.5

176.9

156.9

Zn328.18

34.51

41.99

38.40

226.35

239.3

229.4

200.8

Zn629.48

36.79

45.30

38.39

290.12

310.2

302.6

241.3

Zn929.45

35.65

40.53

34.05

342.76

341.0

320.6

244.8

Zn1226.35

32.49

37.00

31.76

358.61

347.7

333.8

248.0

Source: Jain and Dahama, 2007

Effect of P and Zn and their interaction on available P and Zn content of soil

TreatmentAvailable phosphorus (kg/ha) Available zinc (ppm)

P0 P30 P60 P90 P0 P30 P60 P90

Zn019.99

28.63

35.59

42.91

0.565 0.445 0.304 0.213

Zn3 17.74 25.64 32.86 38.08 1.005 0.887 0.741 0.522

Zn6 15.49 23.08 29.77 34.57 1.315 1.132 0.974 0.811

Zn9 13.36 20.05 26.90 31.32 1.525 1.366 1.250 0.943

Zn12 11.37 16.21 25.60 27.34 1.675 1.573 1.441 1.064

Source: Jain and Dahama, 2007

Effect of P and Zn and their interaction on grain and straw yield of wheat

Treatment

Grain yield (kg/ha) Straw yield (kg/ha)

P0 P30 P60 P90 P0 P30 P60 P90

Zn0 2909 3437 3990 3959 4931 5508 6336 6279

Zn3 3242 3858 4386 4173 5387 6091 6867 6754

Zn6 3566 4271 4907 4320 5776 6655 7431 7054

Zn9 3772 4325 4491 4017 6241 6685 7026 6235

Zn12 3599 4036 4200 3837 6122 6342 6647 6017

Source: Jain and Dahama, 2007

Effect of treatments on grain and straw yield of soybeanZinc levels

Phosphorus levels MeanP0 P25 P50 P75 P100

Grain yield (q ha-1)Zn0 7.84 10.49 19.40 16.05 14.05 13.57Zn2 11.88 19.81 23.34 20.00 11.69 17.14Zn4 11.51 19.91 25.16 20.35 16.85 18.63Zn6 16.57 23.48 30.44 24.19 12.98 21.53Mean 11.95 16.02 24.54 20.15 13.89

Straw yield (q ha-1)Zn0 19.50 26.13 31.00 32.67 23.91 26.64Zn2 22.52 32.53 35.72 33.64 21.82 29.25Zn4 23.23 35.31 42.40 36.56 30.16 33.53Zn6 28.12 36.00 46.98 46.09 24.60 36.36Mean 23.34 32.49 39.93 37.72 25.12Khamparia and Pitre,

1996

Management strategies Application of Zn fertilizers or Zn-enriched NPK fertilizers

Foliar or combined soil + foliar application of Zn fertilizers under field conditions are highly effective and very practical way to maximize uptake and accumulation of Zn in cereal grain

Zinc-enriched grains results in better seedling vigour, denser stands and higher stress tolerance on potentially zinc-deficient soils.

Effect of different Zn application methods on Zn concentration in whole shoots and grain, and the increases in shoot biomass and grain yield of wheat

Source: Yilmaz et al., 1997

Efect of various Zn application methods on grain zinc concentration of wheat

Source: Yilmaz et al., 1997

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