Effect of Lime on Availability of Phosphorus in Zamorano Soils1

ABDUL BAKI AwAN2

ABSTRACT

Field studies were conducted over a 2-year period onexperimental plots at the Escuela Agricola Panamericanasituated in the valley of the Rio Yeguare at El Zamorano,Honduras, to study the effect of lime on the availabilityof soil P.

Yields of corn (Zea mays), sorghum (Sorghum vulgare),beans (Phaseolus vulgaris), and cowpea (Vigna sinensis)green manure were recorded. Highly significant yield in-creases were obtained when the acid soil (pH 5.5) waslimed to raise the pH to 6.5. The highest yields were ob-tained on plots receiving both lime and P.

The major portion of the potentially available P inZamorano soils is in the organic fraction. Analysis of thefinal soil samples showed that liming liberated the Plocked up in the organic form and increased the efficiencyof applied P for crop use.

In recent years the problem of liming acid soils of thetropics has received some attention. Ignatieff and Lemos(5) have stated that, in the tropics, crops do not alwaysrespond to liming at pH's to which they would respondin temperate regions. Hardy (4) working with some sugar-cane soils in British Guiana found that the effect of lim-ing was highly beneficial. Russell (10) reported that inthe tropics and subtropics liming only improves crop yieldson very acid soils, and usually reduces yields on moder-ately acid soils.

The object of this investigation was to determine theeffect of lime on the availability of P in Zamorano soilsas measured by crop response and soil analysis.

MATERIALS AND METHODSThe experimental plots were located at the Escuela Agricola

Panamericana, El Zamorano, Honduras. The area has an ele-vation of 2,600 feet above sea level, an average annual rain-fall of 45 inches with the majority falling between the monthsof May and November, and annual temperature ranges from51° to 88° F.

LIMING ACID SOILS is a common practice in the humidregions of the temperate zone and the studies of vari-

ous workers (2, S, 8, 11) indicate that lime helps to in-crease the availability of P to plants. The soils of thetropics have not been studied as closely as temperatesoils and our knowledge about these soils is limited.

Table 1—Physical and chemical properties of the soilsfrom two locations used in this study.

Soil properties

ColorOrganic matter ( %)PHPhosphorus, ppm.

Available PTotal PInorganic POrganic P

Texture, %ClaySiltSand

LocationLa Terraza

10YH 5/22.95.5

3.0121.020.0

101.0Clay loam

31.533.435.1

La Vega

10YR 5/23.15.5

3.4131.023.0

108.0Clay loam

36.239.624.2

AWAN: EFFECT OF LIME OF AVAILABILITY OF P IN ZAMORANO SOILS 673

Table 2—Yields of sorghum (NK 320 Hybrid), coi(Cornell 54), and beans (Zamorano) in response to

liming from "La Vega" experimental plots. Thethree crops were grown only once during

1961-63.

Table 4—Analysis of soil P after 2 years of cultivation.(La Vega)

Sorghum,10% moisture

kg. Aa-

Corn,12% moisture

kg./ha.

Beans,10% moisture

kg./ha.CheckLimePLime + P

LSD 0. 01LSD 0. 05

1,9212,6082,6592,932

241159

100131139153

2,2683,5723,3994,245

576381

100158150187

1,1131,7291,5702,065

267175

100155141186

Table 3—Yields of corn (Guatemala 142-56) and cowpea(Victor) green manure in response to liming from "La

Terraza" experimental plots. The two crops weregrown only once during 1961-63.

Corn12% moisture

Cowpe:green manure

CheckLimePLime+ P

LSD 0. 01LSD 0. 05

kg. Aa.

1,5342,6142,6703,921

554367

%100164174256

ton/ha.

6.29.78.4

13.11.40.9

%

100154136213

The physical and chemical properties of the surface soilsfrom two locations used in this study are summarized in Table1. A latin square design was utilized with four treatments:(a) Check, pH 5.5, (b) two long-tons per hectare equivalentof CaCOs as Ca(OH)2 calculated to raise the original pH ofthe soil to 6.5, and applied in the first year only, (c) 35 kg.per hectare P as triple superphosphate, applied at the plantingof all crops except cowpea green manure, and (d) combinationof treatments (b) and (c). All treatments received a uniformapplication of 80 kg. per hectare N as urea except whenplanted with beans and cowpea green manure.

Field studies were conducted over a 2-year period (1961-63)and yields of sorghum (NK 320 Hybrid), corn (Corneli 54),and beans (Zamorano) from "La Vega," and corn (Guatemala142-56) and cowpea (Victor) green manure from "LaTerraza" experimental plots were recorded. Final surfacesamples were collected for the fractionation of P.

The Walkley-Black method (6) was used to determineorganic matter. The soil pH was determined with a glasselectrometric poteniometer on 1:1 soil water mixture afterallowing the suspension to stand for 15 minutes. Sand, silt,and clay analysis were made according to the Bouyoucusmethod (1). The method of Mehta et al. (7) was used forthe determination of total, inorganic, and organic P. Themolybdate blue procedure (12) was used to estimate the Pextracted by the Morgan method (9).

RESULTS AND DISCUSSION

The yields of sorghum, corn, and beans from "La Vega"and of corn and cowoea green manure from "La Terraza"are reported in Table 2 and 3, respectively. Highly sig-nificant increases in yields were obtained from the appli-cation of lime alone and lime together with P. There wasno significant difference in yield between treatments (b)and (c) except for the yields of cowpea green manurewhich were significant at the 5% level. The highest yields

Treatments

CheckLimePLime + P

PH

5.56.35.46.3

LSD Available P

LSD Inorgante P

Phosphorus

(.05)(.01)(.05)(.01)

Available

3.46.06.7

12.04.87.36.29.4

TotalOrganic P,

Inorganic Organic

131 23129149150

363861

LSD Total P

LSD Orj?anlc P

10893

11189

(.05)(.01)(.05)(.01)

7.912.010.616.0

82.472.175.559.3

Table 5—Analysis of soil P after 2 years of cultivation.(La Terraza)

Treatments pH

CheckLimePLime + P

LSD Ai

5.56.25.56.3

liable P

LSD Inorganic P

(.05)(.01)(.05)(.01)

Available

3.05.66.1

13.5

1.21.97.8

11.7

PhosphorusTotal Inorganic Organic

— ——— ppm. ——————————

121 20 IOI120 31 89129 33 96132 55 77

LSD Total P

LSD Organic P

Organic P,

% of total

83.574.274.458.3

(. 05) 9.

(. 05) 10.(.01) 15.

0

47

in all crops were obtained when lime and P were usedtogether.

The results of the analysis of soil P at the end of 2years are shown in Tables 4 and 5. The data shows thatthe major part of the potentially available P in Zamoranosoils is in the organic form. Liming of these acid soilsliberated soil P from the organic fraction and increasedthe efficiency of the applied P for crop use.