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Poster61: Dynamics of nitrogen and phosphorus in Quensungual slash and mulch agroforestry system

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Poster for CIAT 2009 Knowledge Sharing Week

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Poster61: Dynamics of nitrogen and phosphorus in Quensungual slash and mulch agroforestry system

  1. 1. 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.

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