Soil-Plant System Response to Lime and P Fertilizer Amendments in an Andisol in the Ecuadorean Andes

Kathleen Webbera, Soraya Alvarado Ochoab, Richard Stehouwera, Danny Faríasb

Penn State Universitya, INIAPb

Andisols are soils derived from volcanic ash that make up a mere 1% of the world’s soils. They are geographically localized to regions marked by volcanic activity, including the Andean Highlands of Ecuador, part of the Ring of Fire. Andisols have high organic matter content, high water holding capacity, and high overall native fertility as a result of their unique parent material. However, high rates of phosphorus sorption are also characteristic of many volcanic soils (Andisols) and can limit agronomic productivity. Acid Andisols, like those evaluated in this experiment, experience phosphorus sorption as a result of ligand bonding with amorphous minerals and organic matter, and fixation of phosphate with aluminum and iron oxides. Phosphate removed from the soil solution is strongly held by soil minerals and is not available to plants.

The major objective of our work was to investigate the use of lime and P fertilizer amendments in order to reduce P sorption, increase P bioavailability, and increase plant P uptake and biomass production.

Here we report on the immediate results of this work and potential long-term benefits of application of these amendments to acid Andisols that have high rates of P sorption.

Introduction & Objectives

General properties of a soil within the watershed of the Chimbo River within the SANREM study site in Ecuador was selected to be used in a greenhouse experiment:

Nine treatments were established in the greenhousestudy using three rates each of lime and phosphorus:

Plant tissue was digested in nitric-perchloric acidsolution while soil samples were analyzed in a Modified Olsen and a Mehlich-3 solution.

Materials & Methods

Results

The use of lime is shown by the plant bioindicators to have a positive effect on biomass production, however, the same treatments were shown to have no effect or a negative impact on available soil phosphorus. This discrepancy highlights the need for future development and calibration of a soil test for this region.

Plant nutrition, including tissue calcium, iron, and others concentrations were all improved for the plant with the use of lime. Plant P concentrations nor uptake changed due to liming.

The use of lime in these volcanic soils to improve the long-term phosphorus availability is a potential theme for future work on this subject. Results from our tests show an improved phosphorus desorbability over time with liming, in addition to the increased P availability directly linked to the addition of P fertilizer.

Conclusions

0x Lime Rate

0P 1P 2P

0P 1P 2P

1x Lime Rate

0P 1P 2P

2x Lime Rate

Measurement Result

pH 5.88

Olsen extractable P 6.32 mg/kg

Aluminum (Mehlich-3) 1707.9 mg/kg

Iron (Olsen) 927.42 mg/kg

Plant Available Water Content 37.2 g H2O/g soil

Organic Matter 13.2%

Texture Silt Loam

Field Rate Applied Rate

Treatment Code Lime P2O5 Lime P2O5

ton ha-1 kg ha-1 g pot-1

T1: 0L, 0P 0 0 0 0

T2: 0L, 1P 0 90 0 0.32

T3: 0L, 2P 0 180 0 0.63

T4: 1L, 0P 3 0 11.74 0

T5: 1L, 1P 3 90 11.74 0.32

T6: 1L, 2P 3 180 11.74 0.63

T7: 2L, 0P 6 0 23.48 0

T8: 2L, 1P 6 90 23.48 0.32

T9: 2L, 2P 6 180 23.48 0.63

Clinopyroxene11.01%

Holmquisite1.50%

Quartz1.70%

Amorphous & Others38.84%

Andesine46.95%

600

700

800

900

1000

1100

1200

1300

1400

1 2 3 4 5

Des

orb

ed P

(m

g P

kg-

1 s

oil)

Sequential Extraction Round

Cumulative P Desorption

T1: 0L, 0P

T2: 0L, 2P

T3: 2L, 0P

T4: 2L, 2Pb

ab

ab

a

0

20

40

60

80

100

T1: 0L, 0P T2: 0L, 2P T3: 2L, 0P T4: 2L, 2PDes

orb

ed P

(m

g P

kg

soil-

1)

Treatment Type

Effect of previous lime and P treatment on desorption of subsequently added P

The use of lime in a first cropping cycle was shown to have an impact on the desorbable phosphorus from the same soils after a secondary phosphorus application, suggesting that liming increases future P availability in these soils.

0

4

8

12

16

20

0 1 2

gra

ms p

ot-

1

Lime Rate

Dry Plant Biomass

0X P Rate1X P Rate2X P Rate

Effect Pr>FL <0.05P <0.05LxP 0.33

0.000

0.005

0.010

0.015

0.020

0.025

0 1 2

gra

ms P

po

t-1

Lime Rate

P Uptake

0X P Rate

1X P Rate

2X P Rate

Effect Pr>FL 0.15P <0.05LxP 0.23

5

10

15

20

25

30

0 1 2

mg

P k

g-1

Lime Rate

Mehlich-3 Extractable P, Time 4

0X P Rate

1X P Rate

2X P Rate

Effect Pr>FL 0.06P 0.28LxP 0.17

5

10

15

20

25

30

0 1 2

mg

P k

g-1

Lime Rate

Olsen Extractable P, Time 4

0X P Rate

1X P Rate

2X P Rate

Effect Pr>FL <0.05P <0.05LxP <0.05

Differences in the amount of phosphorus recovered between the two extracting solutions show variability and theimportance of calibration of results with field data, as well as investigation of new methods for measurement.

0

150

300

450

600

750

900

0 1 2

mg

Fe

kg

-1

Lime Rate

Plant Tissue Fe Concentration

0X P Rate

1X P Rate

2X P Rate

Effect Pr>FL <0.05P 0.21LxP 0.78

0.00

0.20

0.40

0.60

0.80

1.00

0 1 2

% C

a c

on

ten

t

Lime Rate

Plant Tissue Ca Concentration

0X P Rate

1X P Rate

2X P Rate

Effect Pr>FL <0.05P 0.22LxP 0.43

Plant biomass and calcium and iron tissue concentrations were influenced by liming, as well as other micronutrientconcentrations. P fertilizer increased biomass production and P uptake, but P concentration did not change.

Analysis of soil mineralogy gave the above results. Amorpohousminerals, clinopyroxene, and holmquisite all have high variable charge and high rates of P sorption. Andesine is a very typical

plagioclase feldspar developing in volcanic soils.

5.00

5.20

5.40

5.60

5.80

6.00

6.20

6.40

0 50 100

pH

Days after Liming

Soil pH

0X Lime Rate

1X Lime Rate

2X Lime Rate

Lime did increase soil pH (which then decreased over time).

Differences in barley response to lime and phosphorus application are shown.

Young Andisol profile showing many depositional volcanic ash events.