Effect of organic and conventional farming systems on nitrogen use efficiency of potato,maize and vegetables in the Central highlands of Kenya |
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| Affiliation: | 1. Institute of Agricultural Sciences in the Tropics, Hohenheim University, Germany, Garbenstraße 13, 70593 Stuttgart, Germany;2. International Centre for Insect Physiology and Ecology, Kenya, P.O. Box 30772-00100, Nairobi, Kenya;3. Research institute of Organic Agriculture, Switzerland, Ackerstrasse 113, 5070 Frick, Switzerland;4. Kenya Agricultural and Livestock Research Organization – National Agricultural Research Laboratories, P.O. Box 14733-00800, Nairobi, Kenya;1. University of Zimbabwe, P.O. Box MP 167, Mount Pleasant, Harare, Zimbabwe;2. CIMMYT, P.O. Box MP 163, Mount Pleasant, Harare, Zimbabwe;3. Ministry of Agriculture, Weed Research Team, Henderson Research Institute, Private Bag 2004, Mazowe, Zimbabwe;1. University of Zimbabwe, P. O Box MP 167, Mount Pleasant, Harare, Zimbabwe;2. CIMMYT Zimbabwe, P. O. Box MP 163, Mount Pleasant, Harare, Zimbabwe;3. Ministry of Agriculture, Weed Research Team, Henderson Research Institute, P. Bag 2004, Mazowe, Zimbabwe;1. Department of Crop Science, University of Zimbabwe, P. O. Box MP 167, Mount Pleasant, Harare, Zimbabwe;2. Institute for Agricultural Sciences, Plant Nutrition, ETH Zürich, Eschikon 33, 8315 Lindau, Switzerland;3. The University of Queensland, Queensland Alliance for Agriculture and Food Innovation, Leslie Research Facility, Toowoomba 4350, Queensland, Australia;4. International Maize & Wheat Improvement Centre, Zimbabwe, P. O. Box MP 163, Mount Pleasant, Harare, Zimbabwe;1. University of Embu, P. O. Box 6, 60100, Embu, Kenya;2. KU Leuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium;3. Kenyatta University, P. O. Box 43844-00100, Nairobi, Kenya;1. Dept. of Soil, Water, and Climate, University of Minnesota, St. Paul, MN 55108, USA;2. Dept. of Crop Science, College of Agricultural Sciences, São Paulo State University (UNESP), Botucatu, SP, Brazil;3. Center of Tropical Roots and Starches, São Paulo State University (UNESP), Botucatu, SP, Brazil;4. Institute of Plant Production and Protection, Universidad Austral de Chile, Campus Isla Teja, Valdivia, Chile;5. USDA-ARS, Soil and Water Management Research Unit, St. Paul, MN, 55108, USA |
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| Abstract: | Increased per capita food production in the tropics is closely tied to soil organic matter and water management, timely nitrogen (N) supply and crop N use efficiency (NUE) which are influenced by farming systems. However, there is lack of data on the effect of organic farming systems on NUE and how this compares to conventional farming systems under tropical conditions. Therefore, the objectives of this study were to determine the effect of conventional and organic farming systems at low and high management intensities on N uptake and N use efficiency of potato (Solanum tuberosum L.), maize (Zea mays L.), cabbage (Brassica oleracea var. Capitata), kale (Brassica oleracea var. Acephala) and Swiss chard (Beta vulgaris sub sp. Cicla). The organic high input (Org-High) and conventional high input (Conv-High) farming systems are managed as recommended by research institutions while organic low input (Org-Low) and conventional low input (Conv-Low) farming systems are managed as practiced by small scale farmers in the Central highlands of Kenya. The study was conducted during three cropping seasons between October 2012 and March 2014 in an ongoing long-term trial established since 2007 at Chuka and at Thika, Kenya. Synthetic N-based fertilizer and cattle manure were applied at ∼225 kg N ha−1 yr−1 for Conv-High and at ∼50 kg N ha−1 yr−1 for the Conv-Low. Composts and other organic inputs were applied at similar N rates for Org-High and Org-Low. Nitrogen uptake efficiency (NUpE) of potato was highest in Conv-Low and Org-Low at Thika and lowest in Org-High and Org-Low at Chuka site where late blight disease affected potato performance. In contrast, the NUpE of maize was similar in all systems at Chuka site, but was significantly higher in Conv-High and Org-High compared to the low input systems at Thika site. The NUpE of cabbage was similar in Conv-High and Org-High while the NUpE of kale and Swiss chard were similar in the low input systems. Potato N utilization efficiencies (NUtE) and agronomic efficiencies of N use (AEN) in Conv-Low and Conv-High were 11–21 % and 1.4–3.4 times higher than those from Org-Low and Org-High, respectively. The AEN of maize was similar in all the systems at Chuka but was 3.2 times higher in the high input systems compared to the low input systems at the Thika site. The AEN of vegetables under conventional systems were similar to those from organic systems. Nitrogen harvest index (NHI) of potato was similar between Conv-High and Org-High and between Conv-Low and Org-Low. N partitioned into maize grain was similar in all the system at Chuka, but significantly lower (P < 0.001) in Conv-low and Org-Low at Thika site. The NHI of cabbage in Org-High was 24 % higher than that of Conv-High. The study concluded that for maize and vegetables, conventional and organic farming systems had similar effects on NUpE, AEN, NUtE and NHI, while for potato conventional systems improved NUE compared to organic systems. The study recommends that management practices for potato production in organic systems should be improved for a more efficient NUE. |
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| Keywords: | Organic farming systems Conventional farming systems Agronomic efficiency of N use N-uptake efficiency N-utilization efficiency N-harvest index |
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