Various activities
       Digital soil map
     Root crops
     Soil fertility 
     Soil museum
     World food

Fallow research



Research 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.


On-farm 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In Western Kenya population pressure  is very high and shifting cultivation has been replaced by semi-permanent cropping systems.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 scientific publications.

Infiltration_Ochinga.jpg (68539 bytes) Ebukanga_-_Jama_Swinkels_Rao_Barrios.jpg (54845 bytes) Graph_nitrate.jpg (56221 bytes) Deep trenching Sesbania sesban.jpg (73245 bytes)


Bush fallow research - Tanzania

Sisal 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 here for more details.

Brushcutting_sisal.jpg (75588 bytes) Bamba.jpg (51776 bytes)


On-farm 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, click 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. 

Hobu_aerialview.jpg (97053 bytes) Hobu piper.jpg (62255 bytes) maize response to N and P.jpg (98032 bytes) SE9_July_1997_2.jpg (84084 bytes)


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  

, 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 text      poster

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. Offprint

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: 85-90. Offprint

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