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A. Castro1, N. Asakawa1, G. Borrero1, I.M. Rao1, J.C. Menjívar2, E. Barrios3, E. Amézquita4, E. García5 and M. Ayarza4
(1) CIAT-Colombia; (2) National University of Colombia – Palmira; (3) EMBRAPA, Brazil; (4)CORPOICA, Colombia; (5) CIAT-Honduras
Consortium for the Integrated Management of
Soils in Central America
The Quesungual Slash and Mulch Agroforestry System (QSMAS) is a
smallholder production system with a group of technologies for the
sustainable management of soil, water and nutrients in drought-
prone areas in hillsides of the sub-humid tropics.
QSMAS is practiced in southwest Honduras (Central America),
where it has successfully replaced the non-sustainable,
environmentally unfriendly slash-and-burn (SB) traditional system.
The main objective of this study was to determine the effect of the
components of QSMAS and the principles (no SB, permanent soil
cover, minimal disturbance of soil and efficient use of fertilizer) that define its
management on the dynamics of nitrogen (N) and phosphorus (P), and the impact of
these dynamics on the productivity and sustainability of the system in Honduras.
Research was conducted to compare 5 land use systems:
1= Slash-and-burn (traditional production system);
2, 3 & 4= QSMAS of <2 years, 5-7 years and >10 years old, respectively; and
5= Secondary forest (reference land use system)
Measurements included: (1) determination of decomposition and
nutrient release from biomass of trees, shrubs and both annual
crops (Wieder and Lang,1982), using the litterbag technique (Bocock and
Gilbert, 1957); (2) ex situ N aerobic mineralization to measure the
potential conversion of organic N into inorganic forms available for plant uptake
(Anderson and Ingram, 1993); (3) ex situ partition of soil total P to measure the size of
different pools with varying levels of availability, following a sequential fractionation
(Tiessen and Moir, 1993; (4) ex situ size-density fractionation of soil organic matter
(SOM) as indicator of potential functional activity of SOM (Meijboom et al., 1995;
Barrios et al., 1996); (5) ex situ nutrient partitioning of crop biomass, to measure the
contribution of annual crops in the reference site to N and P cycling and balance; and
(6) in situ determination of crop yield in the different land use systems.
SB and QSMAS were managed applying local practices to produce
maize (Z. mays) and common bean (P. vulgaris), with and without
addition of fertilizers. Fertilized treatments include 49 kg N + 55
kg P ha-1 8-10 days after planting (DAP) and 52 kg N ha-1 ~30 DAP
for maize; and 46 kg N + 51 kg P ha-1 8-10 DAP for common bean.
QSMAS plot bordered by forests
regenerated as result of
elimination of slash and burn
ANDERSON JM and INGRAM JSI (eds.). 1993. Tropical soil biology and fertility - A handbook of methods. CAB International,
Wallingford, Oxon, UK. 221p; BARRIOS E, BURESH RJ and SPRENT JI. 1996. Organic matter in soil particle size and density
fractions from maize and legume cropping systems. Soil Biol Biochem, 28(2):185-193; BOCOCK KL and GILBERT OJW. 1957.
The disappearance of leaf litter under different woodland conditions. Plant Soil 9:179–188; MEIJBOOM FW, HASSINK J and
NOORDWIJK M. 1995. Density fractionation of soil macroorganic matter using silica suspensions. Soil Biol Biochem, 27:
1109 –1111; TIESSEN H and MOIR J.O. 1993. Characterization of available P by sequential extraction. In (M.R. Carter, Ed.),
Soil Sampling and Methods of Analysis. pp 75-86. Lewis Publishers, FLA, EEUU; WIEDER RK and LANG EL. 1982. A critique of
the analytic methods used in examining decomposition data obtained from litter bags. Ecology 63, 1636-1642.
This study was part of the project ‘PN15: Quesungual Slash and Mulch Agroforestry
System (QSMAS): Improving crop water productivity, food security and resource quality
in the sub-humid tropics’ funded by the Challenge Program on Water and Food of CGIAR.
It was co-executed by CIAT; MIS consortium (Central America); and National University of
Colombia (Palmira). We thank E. Melo, D. Vásquez, O. Ayala, F.J. Sánchez, J. Quintero,
J.G. Cobo and M.T. Trejo for their contributions to this work.
•Similarities in N dynamics in Quesungual and slash-and-burn systems indicate
that they were equally effective in providing N, although in Quesungual system
it is more the result of a biologically mediated process than of an accelerated
source through burning.
•Compared to slash-and-burn system, P pools of Quesungual system are more
dynamic and favorable for crop production by reducing their flows towards
unavailable forms.
•Based on the availability of nutrients and grain yields over time, Quesungual
system may be recommended as an option to replace the traditional slash-and-
burn system.
S lash and B u rn Q S M A S < 2 Q S M A S 5 -7 Q S M A S > 10
Gra
in y
ield
(t
ha
-1)
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
Nitrogen: Total N content in soil (a) was similar among production
systems, with a tendency to be increased in QSMAS over time. N
mineralization (b) was higher in QSMAS >10 at 8 DAP, just before the
first fertilization. Bars in (a) indicate standard deviation.
Land U se S ys tem
S lash & B u rn Q S M A S < 2 Q S M A S 5 -7 Q S M A S > 10 S ec . F o res t
N c
on
ten
t (m
g N
kg
-1 s
oil)
0
500
1000
1500
2000
2500
3000
3500
LSD 0.05 = ns
In cuba tion (days )
0 4 8 12 16 20 24 28 32
N m
ine
raliz
ati
on
(m
g N
kg
-1 s
oil
0
10
20
30
40
50
S lash & B u rn
Q S M A S < 2
Q S M A S 5 -7
Q S M A S > 10
S ec . F o res t
ns ns ns
Mineralization: Decomposition of (a), and release of N (b) and P (c)
from a mixture of vegetative materials of different quality (good,
intermediate and poor) according to the C:N ratio, were similar
among systems. For QSMAS, this suggest an effective biological
activity and nutrient cycling over time.
P release rate (week-1) DSM0.05=
T im e (w eeks)
0 1 2 4 8 16 32 480 1 2 4 8 16 32 480 1 2 4 8 16 32 48
N r
ele
as
e (
%)
0
20
40
60
80
100
T im e (w eeks)
0 1 2 4 8 16 32 480 1 2 4 8 16 32 480 1 2 4 8 16 32 48
N r
ele
as
e (
%)
0
20
40
60
80
100N release rate per week-1:
Slash and Burn = 0.022
QSMAS <2 = 0.032
QSMAS 5-7 = 0.029
QSMAS >10 = 0.035
Sec. Forest = 0.031
DSM0.05 = ns
P release rate per week-1:
Slash and Burn = 0.043
QSMAS <2 = 0.051
QSMAS 5-7 = 0.052
QSMAS >10 = 0.050
Sec. Forest = 0.051
DSM0.05 = ns
S lash and Burn
Q SM AS <2
Q SM AS 5-7
Q SM AS >10
Sec. Forest
M aize - Q SM AS +F
M aize - S lash and Burn -F
Com m on bean - S lash and Burn -F
Com m on bean - Q SM AS +F
M aize - Q SM AS +F
M aize - S lash and Burn -F
Com m on bean - S lash and Burn -F
Com m on bean - Q SM AS +F
M aize - Q SM AS +F
M aize - S lash and Burn -F
Com m on bean - S lash and Burn -F
Com m on bean - Q SM AS +F
LSD0.05= LSD0.05=0.67 ns
(a) (b)
Land U se S ys tem
S lash & B u rn Q S M A S < 2 Q S M A S 5 -7 Q S M A S > 10 S ec . F o res t
P c
on
ten
t b
y p
oo
l (%
)
0
20
40
60
80
100
L a n d U se S ys te m
S lash & B u rn Q S M A S < 2 Q S M A S 5 -7 Q S M A S > 10 S ec . F o res t
P c
on
ten
t b
y p
oo
l (m
g P
kg
-1 s
oil)
0
5 0
1 0 0
1 5 0
2 0 0
2 5 0
3 0 0
3 5 0
4 0 0
Phosphorus: Total P content (a) in QSMAS increased across time,
while the proportion of organic and inorganic P pools (b) remained
similar among land use systems. AP= Available P; MAP= Moderately
available P; RP= Residual P. TP= Total P (sum of the above)
MAP= 14.5LSD0.05 : AP= 12.7
RP= 24.1
TP= 40.7 LSD0.05: Inorganic P=3.0Organic P= 3.0(a) (b)
Land U se S ys tem
S lash & B u rn Q S M A S < 2 Q S M A S 5 -7 Q S M A S > 10 S ec . F o res t
SO
M c
on
ten
t b
y p
oo
l (g
po
ol
kg
-1 s
oil)
0
1
2
3
4
5
6
7
8
9
10
L a n d U se S ys te m
S lash & B u rn Q S M A S < 2 Q S M A S 5 -7 Q S M A S > 10 S ec . F o res t
SO
M c
on
ten
t (%
)
0
1
2
3
4
5
6
LSD 0.05 = 1.29(a) (b) LM= nsLSD0.05 : LL=2.0 LH= ns
(a)
(c)(b)
Grain yield: Under the traditional practices used to produce maize
and common bean in the SB system (where the source of nutrients are
ashes after burning) and QSMAS (in which nutrients are provided by
fertilizers and biomass from native species of tress and crop
residues), yields of maize were higher in QSMAS (although they
decrease over time). Yields in common bean were consistently low in
SB system and QSMAS due to low yield potential of the landrace used.
Bars indicate standard deviation.
Soil Organic Matter (SOM): Total SOM content (a) in QSMAS increased
over time. The biologically active fraction of SOM (light fraction, LL)
was reduced in the production systems compared with the secondary
forest (b). LM= intermediate fraction and LH= heavy fraction (humus).
T im e (w eeks)
0 1 2 4 8 16 32 480 1 2 4 8 16 32 480 1 2 4 8 16 32 48
Ex
ten
t o
f d
ec
om
po
sit
ion
(%
)
0
20
40
60
80
100
Decomposition rate per week-1:
Slash and Burn = 0.024
QSMAS <2 = 0.031
QSMAS 5-7 = 0.030
QSMAS >10 = 0.030
Sec. Forest = 0.025
DSM0.05 = ns
•Based over a three year time period
•Focused on the TRADITIONAL production systems
(i.e. SB no fertilized and QSMAS fertilized)