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
QSMAS plot bordered by forests
regenerated as result of
The Quesungual Slash and Mulch Agroforestry System (QSMAS) is a elimination of slash and burn SB and QSMAS were managed applying local practices to produce
smallholder production system with a group of technologies for the maize (Z. mays) and common bean (P. vulgaris), with and without
sustainable management of soil, water and nutrients in drought- addition of fertilizers. Fertilized treatments include 49 kg N + 55
prone areas in hillsides of the sub-humid tropics. kg P ha-1 8-10 days after planting (DAP) and 52 kg N ha-1 ~30 DAP
QSMAS is practiced in southwest Honduras (Central America), for maize; and 46 kg N + 51 kg P ha-1 8-10 DAP for common bean.
where it has successfully replaced the non-sustainable, Measurements included: (1) determination of decomposition and
environmentally unfriendly slash-and-burn (SB) traditional system. nutrient release from biomass of trees, shrubs and both annual
The main objective of this study was to determine the effect of the crops (Wieder and Lang,1982), using the litterbag technique (Bocock and
components of QSMAS and the principles (no SB, permanent soil Gilbert, 1957); (2) ex situ N aerobic mineralization to measure the
cover, minimal disturbance of soil and efficient use of fertilizer) that define its potential conversion of organic N into inorganic forms available for plant uptake
management on the dynamics of nitrogen (N) and phosphorus (P), and the impact of (Anderson and Ingram, 1993); (3) ex situ partition of soil total P to measure the size of
these dynamics on the productivity and sustainability of the system in Honduras. different pools with varying levels of availability, following a sequential fractionation
Research was conducted to compare 5 land use systems: (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;
1= Slash-and-burn (traditional production system); Barrios et al., 1996); (5) ex situ nutrient partitioning of crop biomass, to measure the
2, 3 & 4= QSMAS of <2 years, 5-7 years and >10 years old, respectively; and contribution of annual crops in the reference site to N and P cycling and balance; and
5= Secondary forest (reference land use system) (6) in situ determination of crop yield in the different land use systems.
•Based over a three year time period
100
Decomposition rate per week -1: •Focused on the TRADITIONAL production systems
(i.e. SB no fertilized and QSMAS fertilized)
Slash and Burn = 0.024
QSMAS <2 = 0.031
E x te n t o f d e c o m p o s itio n (% )
80
QSMAS 5-7 = 0.030
QSMAS >10 = 0.030 M a ize - Q S M A S + F
Sec. Forest = 0.025 M a ize - Q S M A S + F M a ize - S la sh a n d B u rn -F
60
M a ize - S la sh a n d B u rn -F C o m m o n b e a n - S la sh a n d B u rn -F
DSM0.05 = ns
3 .0 C o m m - n Se aA S S F sh a n d B u rn -F C o m m o n b e a n - Q S M A S + F
M a ize o Q b M n - + la
C o m m - n lae a n - d S Mrn S + F
M a ize o S b sh a n Q B u A -F
40 LSD = 0.67
C o m0.05 o n b e a n - S la sh a n d B u rn -F
m
LSD0.05= ns
C om m on bean - Q S M A S +F
2 .5
G ra in y ie ld (t h a )
-1
20
(a) S la s h a n d B u rn
Q SM AS <2 2 .0
Q S M A S 5 -7
0 Q SM AS >10
012 4 8 16 32 48
S e c . F o re s t 1 .5
T im e (w e e k s )
100 1 .0
N release rate per week -1: 100
P release rate per week -1:
Slash and Burn = 0.022 Slash and Burn = 0.043
QSMAS <2 = 0.032 QSMAS <2 = 0.051 0 .5
80
QSMAS 5-7 = 0.029 80 P release rate (week -1) DSM0.05=
QSMAS 5-7 = 0.052
QSMAS >10 = 0.035 QSMAS >10 = 0.050
N re le a s e (% )
N re le a s e (% )
Sec. Forest = 0.031 Sec. Forest = 0.051 0 .0
60
DSM0.05 = ns 60
DSM0.05 = ns S la s h a n d B u rn Q SM AS <2 Q S M A S 5 -7 Q SM AS >10
40
40
Grain yield: Under the traditional practices used to produce maize
20
20
and common bean in the SB system (where the source of nutrients are
(b)
0
0
(c)
ashes after burning) and QSMAS (in which nutrients are provided by
fertilizers and biomass from native species of tress and crop
012 4 8 16 32 48
012 4 8 16 32 48
T im e (w e e k s ) T im e (w e e k s )
residues), yields of maize were higher in QSMAS (although they
Mineralization: Decomposition of (a), and release of N (b) and P (c)
decrease over time). Yields in common bean were consistently low in
from a mixture of vegetative materials of different quality (good,
SB system and QSMAS due to low yield potential of the landrace used.
intermediate and poor) according to the C:N ratio, were similar
Bars indicate standard deviation.
among systems. For QSMAS, this suggest an effective biological
activity and nutrient cycling over time.
3500 50
LSD 0.05 = ns (a) (b) 6 10
3000 (a) 9 (b) LSD0.05 : LL=2.0 LM= ns LH= ns
s o il)
LSD 0.05 = 1.29
s o il
40 400 5
s o il)
AP= 12.7 8
-1
2500 LSD0.05 : TP= 40.7
-1
(a) (b) LSD0.05: Organic P= 3.0 Inorganic P=3.0
N m in e ra liz a tio n (m g N k g
S O M c o n te n t b y p o o l (g p o o l k g
MAP= 14.5
-1
350
7
N c o n te n t (m g N k g
RP= 24.1 100
s o il)
S O M c o n te n t (% )
30 4
2000
300 6
-1
P c o n te n t b y p o o l (% )
P c o n te n t b y p o o l (m g P k g
1500
80
3 5
20 S la s h & B u rn 250
Q SM AS <2 4
1000 Q S M A S 5 -7
200 60 2
Q SM AS >10
3
10 S e c . F o re s t
500 ns ns ns 150
2
40 1
100 1
0 0
S la s h & B u rn Q SM AS <2 Q S M A S 5 -7 Q SM AS >10 S e c . F o re s t 0 4 8 12 16 20 24 28 32
20 0 0
50 S la s h & B u rn Q SM AS <2 Q S M A S 5 -7 Q SM AS >10 S e c . F o re s t S la s h & B u rn Q SM AS <2 Q S M A S 5 -7 Q SM AS >10 S e c . F o re s t
L a n d U s e S y s te m In c u b a tio n (d a y s )
Nitrogen: Total N content in soil (a) was similar among production 0
S la s h & B u rn Q SM AS <2 Q S M A S 5 -7 Q SM AS >10 S e c . F o re s t
0
S la s h & B u rn Q S M A S < 2 Q S M A S 5 -7 Q S M A S > 1 0 S e c . F o re s t
Soil Organic Matter (SOM): Total SOM content (a) in QSMAS increased L a n d U s e S y s te m L a n d U s e S y s te m
systems, with a tendency to be increased in QSMAS over time. N Phosphorus: Total P content (a) in QSMAS increased across time,
L a n d U s e S y s te m L a n d U s e S y s te m over time. The biologically active fraction of SOM (light fraction, LL)
mineralization (b) was higher in QSMAS >10 at 8 DAP, just before the while the proportion of organic and inorganic P pools (b) remained was reduced in the production systems compared with the secondary
first fertilization. Bars in (a) indicate standard deviation. similar among land use systems. AP= Available P; MAP= Moderately forest (b). LM= intermediate fraction and LH= heavy fraction (humus).
available P; RP= Residual P. TP= Total P (sum of the above)
This study was part of the project ‘PN15: Quesungual Slash and Mulch Agroforestry
•Similarities in N dynamics in Quesungual and slash-and-burn systems indicate System (QSMAS): Improving crop water productivity, food security and resource quality
that they were equally effective in providing N, although in Quesungual system in the sub-humid tropics’ funded by the Challenge Program on Water and Food of CGIAR.
it is more the result of a biologically mediated process than of an accelerated It was co-executed by CIAT; MIS consortium (Central America); and National University of
source through burning. 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.
•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. 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
•Based on the availability of nutrients and grain yields over time, Quesungual fractions from maize and legume cropping systems. Soil Biol Biochem, 28(2):185-193; BOCOCK KL and GILBERT OJW. 1957.
system may be recommended as an option to replace the traditional slash-and- 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:
burn system. 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.