on natural and improved fallows was conducted in Kenya and Papua New
Guinea whereas the long-term effects of bush fallows were
investigated on sisal plantations in Tanzania.
research - Western Kenya
In Western Kenya population
pressure is very high and
shifting cultivation has been
replaced by semi-permanent cropping systems. The soils are highly
weathered and of poor chemical fertility. Short-term fallows with N-fixing
woody perennials may result in an enhanced restoration of soil fertility
and higher crop yields, but the underlying mechanisms remain poorly
understood. We have conducted a series of fieldexperiments with different
fallow vegetations and permanent maize cropping to investigate N dynamics
in such systems. Inorganic N was measured under these different systems at
different depths and the results showed that the improved fallow (Sesbania
sesban) was able to retrieve significant amounts of NO3
below the rooting zone of other crops. My research included the set-up and
management of the field experiments including data collection and
analysis. The research was
conducted on-farm (but researcher-managed) and was an international
collaborative undertaking of ICRAF (soil) scientists. Results were
presented to the farmers in Western Kenya, in various seminars and in
fallow research - Tanzania
growers in Tanzania often leave the land fallow for prolonged periods
(10-20 years) after a cycle of sisal (10 years). It is generally assumed
that the soil fertility is sufficiently restored after such fallow period
to allow for another cycle of sisal without external nutrient inputs. We
sampled sites under different periods of fallow and compared the soil
analytical values to those under permanent sisal cropping. Although there
were differences between soil types it was found that long-term fallows
are insufficient to restore the soil fertility and nutrient inputs and
liming are indispensable for continuous sisal cultivation. Click
research - Papua New Guinea
In 1996, I initiated
a series of on-farm experiments investigating (i) the biomass and
nutrient accumulation of piper and other fallow vegetation (piper
imperata, gliricidia, click here
for more details), (ii) the effects of these different fallows on sweet potato
and maize yield, and (iii) changes in soil properties in these systems.
The experiments were conducted on-farm and researcher-managed. Exciting
results were obtained including the finding that sweet potato yields were
reduced in wetter seasons whereas fallow biomass accumulation was
decreased in drier seasons. This was the first process-oriented research
on the effects of fallow on root and tuber crops in Papua New Guinea,
here for details.
During the experiments it became apparent that input from other scientists
was needed and an entomologist and plant pathologist were involved in the
trials which enhanced the capacity to explain some of the results and
yielded a solid set of experimental data. Funding came from ACIAR and the
University of Technology in Lae.
Hartemink, A.E. 2004 Nutrient stocks of short-term fallows on high
base status soils in the humid tropics of Papua New Guinea. Agroforestry
Systems 63: 33-43
Hartemink, A.E. 2003 Integrated nutrient management research with sweet
potato in Papua New Guinea. Outlook on Agriculture 32: 173-182
Hartemink, A.E. 2003
Sweet potato yield and nutrient dynamics after
short-term fallows in the humid lowlands of Papua New Guinea. Netherlands
Journal of Agricultural Science 50: 297-319
Hartemink, A.E. 2002 Nutrient stocks and nutrient cycling of fallows in
the humid lowlands of Papua New Guinea. 17th World Congress of Soil
Science, Vol. II: 691. IUSS, Bangkok
Hartemink, A.E. 2001
Biomass and nutrient accumulation of Piper aduncum
and Imperata cylindrica fallows in the humid lowlands of Papua New Guinea.
Forest Ecology and Management 144: 19-32
Hartemink, A.E. & J.N. O’Sullivan 2001
Leaf litter decomposition of Piper
aduncum, Gliricidia sepium and Imperata cylindrica in the humid lowlands
of Papua New Guinea. Plant and Soil 230: 115-124
Hartemink, A.E., S.
Poloma, M. Maino, K.S.
Powell, J. Eganae & J.N. O’Sullivan
2000 Yield decline of sweet potato in the humid lowlands of Papua New
Guinea. Agriculture, Ecosystems and Environment 79: 259-269
Hartemink, A.E., R.J.
Buresh, P.M. van Bodegom, A.R.
Braun, B. Jama & B.H.
Janssen 2000 Inorganic nitrogen dynamics in fallows and maize on an Oxisol
and Alfisol in Kenya. Geoderma 98: 11-33
Louman, B & A.E.
Hartemink 1998 Sweet potato production in hedgerow
intercropping systems in the lowlands of Papua New Guinea. Papua New Guinea
Journal of Agriculture, Forestry & Fisheries 41: 91-98.
Sayok, A. & A.E.
Hartemink 1998 Erosion and soil fertility changes under
leucaena intercropped with sweet potato in the lowlands of Papua New
Guinea. Papua New Guinea Journal of Agriculture, Forestry & fisheries 41:
Hartemink, A.E., J.F.
Osborne & Ph.A. Kips 1996
Soil fertility decline and
fallow effects in Ferralsols and Acrisols of sisal plantations in
Tanzania. Experimental Agriculture 32:173-184
Hartemink, A.E., R.J.
Buresh, B. Jama & B.H.
Janssen 1996 Soil nitrate and
water dynamics in sesbania fallows and weed fallows. Soil Science Society
of America Journal 60: 568-574