Short-term green manure and tillage management effects on

maize yield and soil quality in an Andisol

M. Astier a,*, J.M. Maass b, J.D. Etchevers-Barra c,J.J. Pena d, F. de Leon Gonzalez e

a Grupo Interdisciplinario de Tecnologıa Rural Apropiada A.C., Col. Morelos, Local 17 Centro Comercial el Parian,

Apartado Postal 152, 61609 Patzcuaro, Michoacan, Mexicob Centro de Investigacion en Ecosistemas, UNAM, Campus Morelia, Apartado Postal 27-3, Morelia, Michoacan 58190, Mexico

c Laboratorio de Fertilidad de Suelos, Colegio de Postgraduados, Montecillo 56230, Estado de Mexico, Mexicod Departamento de Biotecnologıa y Bioquımica, CINVESTAV, Unidad Irapuato, Apartado Postal 36500, Irapuato, Guanajuato, Mexico

e Departamento de Produccion Agrıcola y Animal, Universidad Autonoma Metropolitana-Xochimilco, Calzada del Hueso 1100,

Col. Villa Quietud 04960, D.F., Mexico

Received 23 July 2003; received in revised form 13 May 2005; accepted 17 May 2005

Abstract

Andisols are very important land resources supporting high human population density. Maize (Zea mays L.) production on

Andisols located in the Purhepecha Region of central Mexico is representative of the highlands conditions of Mexico and Latin

America. Farmers struggle with low crop yield and low soil nutrient availability. A 2-year field study was conducted to evaluate

the effects of green manures either tilled into the soil (CT) or cut and left on the surface as a mulch (ZT), on maize yield and soil

quality. Green manure treatments were: vetch (Vicia sativa L.), oat (Avena sativa L.) and none. No extra N was added to maize.

Green manure and tillage had a significant effect on maize grain yield, N uptake and P uptake with CT vetch performing better

than ZT oat. Soil organic C and total N were significantly higher under ZT than under CT management. Soils with vetch had

higher P concentration. Soil under ZT oat had the highest infiltration rate and penetration resistance compared with other

treatments. There appears to be a trade off between soil productivity and intrinsic soil physical properties among soil treatments.

# 2005 Elsevier B.V. All rights reserved.

Keywords: Andisol; Green manure; Soil indicators; Soil quality; Tillage

www.elsevier.com/locate/still

Soil & Tillage Research 88 (2006) 153–159

1. Introduction

Andisols occur in populated and important agri-

cultural areas all over the world (Shoji et al., 1993).

* Corresponding author.

E-mail address: mastier@oikos.unam.mx (M. Astier).

0167-1987/$ – see front matter # 2005 Elsevier B.V. All rights reserved

doi:10.1016/j.still.2005.05.003

These soils are characterized by high amount of

organic matter; very low rate of N and P mineraliza-

tion; high P adsorption levels and fragile physical

properties when converted to agriculture and mechan-

ical tillage. Agricultural practices such as CT and

inappropriate fertilization are causing gradual dete-

rioration of Andisols in the Purhepecha Region of the

.

M. Astier et al. / Soil & Tillage Research 88 (2006) 153–159154

Table 1

Soil characteristics in Casas Blancas, Michoacan, Mexico

Characteristics 0–10 cm 10–20 cm

Texture (%)

Sand 46.3 51.3

Silt 35.0 31.2

Clay 18.8 17.5

Bulk density (g cm�3) 0.63 0.60

P retention (%) 98

PH–H2O (1:2:5) 6 6

Organic matter (%) 9.4 8.9

Organic carbon (mg C g�1 soil) 54.5 51.5

Total nitrogen (mg N g�1 soil) 3.8 3.6

Available phosphorous

P Bray (mg P g�1 soil) 1.3 0.9

P Olsen (mg P g�1 soil) 8

Exchangeable cations (mg g�1)

Ca++ 1396 1595

Mg++ 111 129

K+ 285 248

Na+ 2.0 4.5

Mexican highlands (Santos-Ladın, 1986). In this

region, 2.4–3.0 Mg ha�1 of conventionally tilled soils

are lost every year due to erosion (Tiscareno et al.,

1999) with depletion of macronutrients, from the

agricultural fields. Farmers need to add increasing

amounts of N as chemical fertilizer to maintain maize

yields (Astier et al., 2000).

Green manuring is the process of turning a crop into

the soil, whether originally intended or not, irrespec-

tive of its state of maturity, for the purpose of affecting

some agronomic improvement (Mac Rae and Mehuys,

1985). Green manures are known to increase soil N

and P availability for the following crop and at the

same time, contribute to the conservation of soil

organic matter and soil biological, physical and

chemical properties (Mac Rae and Mehuys, 1985;

Mc Vay et al., 1989).

Acton and Gregorich (1995) defined soil quality as

the condition of a soil to maintain plant growth

without soil degradation or environmental damage.

Soil quality evaluation frameworks must be sensitive

to the specific time and spatial scale of the study

(Astier et al., 2002).

The objective of this study was to evaluate

transitional effects over 2 years on soil productivity

and soil quality resulting from green manure species

and tillage management. For that purpose, the best

(most sensitive) indicators were selected.

2. Materials and methods

2.1. Experimental site and design

An experiment was conducted at Casas Blancas,

Michoacan (198250N, 1018360E, altitude of 2298 m)

in the Lake Zirahuen Watershed within the Pure-

pecha Region of Mexico from 1996 to 1998. The

region is sub-humid with rains from May to October.

Average annual rainfall is 1100 mm and annual

temperature is 14 8C with early frost events and hail

storms. The soil is an Andisol Humic and Ocric

(Table 1). The field was under natural vegetation

(mainly grasses) and without plowing for more than

6 years before the experiment was established. The

design was a complete randomized block with five

replicates of each treatment. Each plot measured

15 m � 15 m.

2.2. Green manure and crop management

The experiment consisted of a green manure-maize

rotation from July of 1996 until the end of the growing

season of 1998. Tillage management treatments and

green manure species were: (1) conventional tillage

with no green manure or fertilization (CCT); (2)

conventional tillage with vetch (VsCT); (3) zero

tillage with vetch (VsZT); (4) conventional tillage

with oat (AsCT) and zero tillage with oat (AsZT). The

green manure and maize establishment sequence was

the following: green manure in July 1996 and maize in

April 1997; green manure in November 1997 and

maize in April 1998. Plots with vetch and oat were

established at a seed rate of 100 and 200 kg ha�1,

respectively. At 20% flowering time, these green

manures were either tilled into the soil with a hand-hoe

in the manner of a chisel plough (CT), or cut and left

on the surface as a mulch (ZT). Phosphorous fertilizer

was added to the vetch and oat with the purpose of

increasing biomass accumulation of both green

manures and maximizing biological N fixation of

the vetch (Flach et al., 1987; De Leon and Etchevers-

Barra, 1999). Triple super phosphate (TSP, 46% P2O5)

was broadcasted at 100 kg ha�1 at seeding time and

incorporated into the soil with a hand-hoe in both CT

and ZT. To prevent contamination, a buffer zone 3 m

M. Astier et al. / Soil & Tillage Research 88 (2006) 153–159 155

wide cultivated with oats was established between

blocks. Average biomass accumulation of vetch and

oat for the 2 years of cultivation was 2.3 and

6 Mg ha�1, respectively. Vetch had significantly

higher N and P tissue concentration than oat, with

C to N ratio for vetch and oat of 13 and 27,

respectively (Astier, 2002).

In mid-April maize was sown and managed under

either CT or ZT in 1997 and 1998. Maize, local variety

‘‘criolla’’, was sown within the first 10 cm depth

40 cm apart within the row and 70 cm between rows.

Andisols are able to keep enough residual moisture to

allow germination of seeds. Sporadic rains and

morning dew occur during the 6 months period before

maize sowing time. Maize plants were thinned to two

plants per hole 6 weeks after sowing. Weeding was

done by hand hoeing. In October, all maize plants

were cut and piled up outside the experimental plots.

Ears and fodder were harvested in mid-December.

This was done to simulate the regional practice of

using stalks as cattle forage.

2.3. Selection of indicators

Indicators of soil quality were selected based on:

(1) agronomic and environmental quality objectives

and (2) the critical negative points identified in the

agricultural system (Astier et al., 2002). Identification

of critical points and selection of indicators were done

using participatory research between farmers and

technicians working in the community of Casas

Blancas (Astier et al., 2000). The most sensitive

indicators selected, which reflected transitional

changes in soil N and P availability, maize yield

and soil quality were: dry matter (DM) of maize, N

and P uptake of maize, soil organic carbon (SOC), soil

total N (STN), P-Olsen, pH, infiltration rate, penetra-

tion resistance, water content and moisture retention.

2.4. Data collection for maize yield and soil

quality indicators

Above ground total DM and grain yield of maize

were determined by hand-harvesting all plants in each

of the plots. Plant samples were dried at 70 8C for

48 h, then ground to pass a 1 mm mesh screen. These

samples were analyzed for N and C concentration by

the flash combustion using a NC2100 Soil Analyser.

Plant material was digested with nitric acid and P

determined by a colorimetric procedure. Total N and P

uptake at harvest was calculated based on DM and

nutrient concentration of above-ground biomass,

summed for grain and stover components.

Five composite soil samples were collected (25 cm

depth) from each plot. The sampling was performed

annually at the beginning of the experiment 60 and 210

days after sowing, and after maize harvest. Soil samples

were sieved at 2 mm and air-dried until constant air-

dried weight was achieved. Soil available P, SOC and

STN were determined on <2 mm soil fraction.

Soil pH was measured in a 1:5 (w/v) aqueous

suspension. Soil samples were also analyzed for N, P,

and organic C concentrations. The analyses were done

following the methods by Olsen and Dean (1965) for

available P, the Kjeldahl’s method for STN and a wet

combustion procedure (Nelson and Sommers, 1982)

for SOC.

Penetration resistance was measured with a manual

Soil Compaction Tester (Dickey-John Corporation;

force capacity of 100 kg cm2) and an electronic

penetrometer (Bush SP1000 ELE; force capacity of

50 kg). Penetration resistance was expressed in PSI for

the manual device and in MPa for the electronic device.

Infiltration was estimated at the end of the

experiment using a metal infiltration ring (0.20 m

diameter) introduced into the soil 0.5 m; water

infiltration (0.01 m) was recorded two times (Bouwer,

1982). This procedure was repeated three times per plot.

In November 1998, at the end of the rainy season,

soil water content and soil water retention were

determined. Soil water content was determined

gravimetrically after drying the samples at 105 8Cto a constant mass. Water retention was measured at

0.1–4 bar in pressure chamber.

Analysis of variance was performed for all

response variables using SAS (SAS Institute Inc.,

1989). Means were separated using least significant

difference (LSD) at P = 0.05.

3. Results and discussion

3.1. Maize yield and N and P maize content

There was a significant effect of green manure on

maize grain, stover, and total DM. Vetch cover crop

M. Astier et al. / Soil & Tillage Research 88 (2006) 153–159156

Table 2

Effect of green manure (GM) and tillage (T) on dry matter yield, N and P content and N and P uptake of maize

Treatment Dry matter

(kg ha�1)

Nitrogen concentration (g kg�1) Phosphorous

concentration

(g kg�1)

Total nitrogen

uptake (kg ha�1)

Total phosphorous

uptake (kg ha�1)

Stover Grain Total yield Stover Grain Stover Grain

VsCT 5534 aa 1782 a 7317 a 5.5 a 14 a 0.82 c 2.6 a 56 a 9.5 a

AsCT 4270 ab 948 bc 5217 b 5 a 14 a 0.92 c 2.3 a 35 bc 6.4 bc

VsZT 5261 a 1112 b 6373 ab 5 a 13.7 a 1 b 2.6 a 44 ab 8.6 ab

AsZT 2716 bc 461 c 3176 c 5 a 14 a 1.6 a 2.2 a 20 cd 5.5 cd

CCT 1960 c 514 bc 2474 c 5.7 a 12.3 a 1 b 2 a 17.6 d 3 d

ANOVA

GM * * ** NS NS ** NS ** *

T NS * * NS NS ** NS * NS

GM � T NS NS NS NS NS ** NS NS NS

Average of 1997 and 1998; As and Vs refer to oat and vetch, respectively. CT and ZT refer to conventional and zero tillage, respectively.a Means with the same letter(s) (a, b, c) within the same column are not significantly different at P � 0.05 (LSD).* Significant at P < 0.05.

** Significant at P < 0.001.

produced higher maize yield than oat cover crop

(Table 2). Soil tillage had a significant effect on maize

grain and total DM production. Yield of both grain and

stover were higher in CT than in ZT. Dou et al. (1994)

determined that N supplied by green manures left on

the soil surface as a mulch during the first year of a

field experiment was insufficient for reaching max-

imum maize growth.

Nitrogen concentration of maize stover and grain

components was unaffected by green manure and

tillage. However, both practices had a significant

effect on P concentration in stover. Maize stover in

AsZT had the highest P concentration, perhaps as a

result of the low stover DM production. Phosphorous

concentration in grain was unaffected by treatments

(Table 2).

Maize N uptake was significantly affected by green

manure and tillage. Higher N uptake was observed

with either green manure compared without. Maize

grown with vetch had significantly higher N uptake

than with oat. The difference could be attributed to

greater soil N availability due to biological N fixation

with vetch (Table 2). Legumes can increase the

content of soil mineral N in the long run in comparison

with the non-legume monocrop systems (Wani et al.,

1995). Sarrantonio and Scott (1988) found in a 2-year

experiment that maize yield was significantly higher

with CT than with ZT, and both maize yield and N

uptake were significantly higher following vetch than

without cover crop under either ZT or CT manage-

ment. In longer term experiments, maize under ZT can

produce equivalent or higher yield than maize under

CT (Tiscareno et al., 1999).

Green manure influenced P uptake, but tillage did

not. Maize grown with vetch had higher P uptake than

maize grown with oat or without green manure

(Table 2).

Application of high-quality organic inputs (i.e.,

certain legumes with low lignin and low C/N ratio,

such as vetch), could provide a more efficient use of

nutrients by releasing nutrients quickly to short-cycle

food crops (Sanchez, 1989). This would be the result

of rapid turnover of active soil organic matter that

releases nutrients in synchrony with plant demand.

Rapid turnover could help to explain higher grain yield

and N and P uptake in maize when vetch rather than

oat preceded this crop. Application of lower quality

plant residues (high in lignin or polyphenolics and low

in N), such as oat, can maintain or increase SOC, and

build-up soil organic N in the slowly turning pool

(Warman, 1980; Sanchez, 1989).

3.2. Soil chemical properties

At the end of the experiment, tillage had an effect

on SOC concentration but green manure did not. Soil

under ZT had higher SOC concentration than under

CT (Table 3). Buried organic residues often decom-

M. Astier et al. / Soil & Tillage Research 88 (2006) 153–159 157

Table 3

Effects of green manure (GM) and tillage (T) management on soil physico-chemical properties of 0–25 cm layer at the end of the experiment

Treatment Organic-C

(g kg �1)

Total N

(g kg�1)

P (mg g�1) pH (H2O) Infiltration time (s)

of 500 ml

Water

content (%)

Penetration

resistance (Psi)

VsCT 46 ba 3.4 b 18.0 a 6.26 b 40 aa 45 a 276 b

AsCT 49 ab 3.4 b 9.4 c 5.78 d 33 a 44 a 268 b

VsZT 50 a 3.8 a 16.4 b 6.00 b 27 b 43 a 232 cd

AsZT 50 a 3.8 a 9 c 5.90 c 17 c 43 a 204 d

CCT 49 ab 3.6 ab 6 d 6.5 a 43 a 40 a 325 a

ANOVA

GM NS NS ** ** * NS NS

T * ** NS NS ** NS **

GM � T NS NS NS ** NS NS NS

November, 1998; As and Vs refer to oat and vetch, respectively. CT and ZT refer to conventional and zero tillage, respectively.a Means with the same letter(s) (a, b, c) within the same column are not significantly different at P � 0.05 (LSD).* Significant at P < 0.05.

** Significant at P < 0.001.

pose faster than when left on the surface (Beare et al.,

1992). Our results are consistent with those from a 5-

year experiment on an Andisol managed with ZT and

CT (Roldan et al., 2003). Maize stubble, an important

organic C source was removed from the experimental

plots to simulate cattle fodder consumption. Oat, used

as green manure preceding maize, produced higher

biomass than vetch and could have alleviated potential

differences in SOC between green manure treatments.

Soil total N mimicked SOC, similar to the results of

other studies (Salinas-Garcia et al., 1997). Higher

STN concentrations were found under ZT than under

CT, under both vetch and oat (Table 3).

Soils under vetch and oat were fertilized with P at

the same rate, but available soil P increased with vetch

compared with oat green manure, both of which were

greater than no green manure (Table 3). Organic

matter additions, e.g. green manures, are expected to

increase P availability in P-fixing soils (Tiessen,

1989). Touchton et al. (1982) and Hargrove (1986)

suggested that P mineralized from a legume may be a

significant source of available P. Paniagua et al. (1995)

in a 10-year cultivation study in volcanic soils

determined that extractable NaHCO3–P and maize

yield were higher in soils treated with legume as green

manure without P fertilization than in soils receiving P

fertilizer in the absence of legume. Higher biomass

accumulation and P concentration in vetch in

comparison with oat could explain higher available

P in soil with vetch than with oat (Astier, 2002).

Green manure addition also had an effect on soil

pH, which was significantly lower in soil under oat and

vetch than under the control (Table 3). Soil under

vetch had higher pH than under oat. A green manure

by tillage interaction was observed for soil pH. The net

effect of nodulated legumes is to lower pH in soils with

pH above the range for optimum growth and

development (Nyatsanga and Pierre, 1973). However,

the effect of different sources of green manure on acid

soils, such as these Andisols, requires further study.

3.3. Soil physical properties

Several previous investigations have found rapid

changes in soil organic matter levels, compaction

and infiltration in agricultural systems with and

without soil cover (Mc Vay et al., 1989; Roldan

et al., 2003). In our study, water infiltration was

affected by green manure and tillage treatments. Soil

under oat had more rapid infiltration than under

vetch (Table 3). Soil under ZT had more rapid

infiltration than under CT. These results are

consistent with a previous regional study (Gomez-

Tagle, 2001, personal communication).

Soil managed under ZT had lower penetration

resistance than under CT (Table 3). Penetration

resistance was greatest below 18 cm under CCT

(Fig. 1). There was no difference in water content

(Table 3) or water retention (Fig. 2) among treatments.

M. Astier et al. / Soil & Tillage Research 88 (2006) 153–159158

Fig. 1. Soil penetration resistance using an electrical device. LSD(P = 0.05) for treatment = 0.03 MPa; LSD(P = 0.05) for depth = 0.31 MPa. VsCT:

vetch under conventional tillage; AsZT: oat under zero tillage and CCT: conventional tillage with no green manure.

Fig. 2. Moisture retention of soil at depth of 0–25 cm as affec-

ted by green manure (As is oat and Vs is vetch) and tillage

(CT is conventional and ZT is zero). No differences (P = 0.05)

occurred.

4. Conclusions

Growth of a cereal (oat) and a legume (vetch) as

green manure in this Andisol generally improved

maize productivity and soil physico-chemical indica-

tors. Vetch cover crop produced higher maize yield

than oat cover crop. Higher N and P uptake was

observed with either green manure than without.

However, maize grown with vetch had significantly

higher N and P uptake than with oat. Vetch

substantially increased soil P availability. Oat had

positive effects on water infiltration and mechanical

resistance indicators. Therefore, to avoid negatively

affecting maize productivity, which is related with

food self-sufficiency in rural communities of this

Mexican region, incorporation of oat as a green

manure must be complemented with a source of

organic or inorganic N.

This study also showed that tillage had an effect on

SOC and STN concentration but green manure did not.

Soil under ZT had higher SOC and STN concentration

than under CT. Soil physical properties, such as

softness and infiltration rate also had higher values

under ZT than under CT.

There appears to be a trade off between maize

productivity and soil properties, at least in the short-

time transition to ZT. Soil under VsCT produced

highest maize yield, whereas soil under AsZT had

highest soil physical indicators. It is important to

emphasize that more than 2 years would be required to

show the real long-term benefits of conservation

management.

Acknowledgements

Plant analyses were conducted at the ‘‘Centro

Internacional de Mejoramiento de Maiz y Trigo’’

(CIMMYT) Plant and Soil Laboratory. Soil analyses

were done at the Soil Fertility Laboratory of the

Colegio de Postgraduados, Mexico. Research for this

project was partly funded by the Grant ‘‘SEMARNAT-

CONACyT 2002-CO1-0800 MESMIS: EVALUA-

CION DE SUSTENTABILIDAD’’.

M. Astier et al. / Soil & Tillage Research 88 (2006) 153–159 159

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