| dc.description.abstract | In Kenya, decline in food production has been a major problem facing smallholder farmers.
The main production constraint being declining soil fertility. It is believed that judicious
management and balanced application of plant nutrients is a strategy that can be employed to
overcome soil fertility decline constraints. This strategy was incorporated in this study.
Balanced fertilization of nitrogeneous, phosphatic and potassium fertilizers were used to
improve yield and quality of Kale, Brassica oleraceae var acephala.
A randomized complete block experiment was set up m 2001 in the greenhouse at the
National Agricultural Research Laboratories (NARL) at Kabete with an overall objective of
determining agro-economic potassium application levels (rates) in the production of Kales.
The first specific objective was to determine the potassium fertilizer application on the
growth, yield and quality of kale and to what extent its omission limited yields. The second
objective was to determine K uptake and partitioning following K fertilization and its effect
on quality of Kale.
Field and greenhouse experiments were conducted to determine the effects of various
treatments. One field experiment was conducted at Kerugoya while two greenhouse
experiments were conducted using Mumias and Kerugoya soils, respectively. Soils from
Mumias and Kerugoya sites were markedly contrasting with respect to agro-ecological and
physico-chemical conditions. Kerugoya soils were better than Mumias in terms of soil
fertility resulting in better performance of kale.
Results obtained indicated that under optimum Nand P soil status, 75 - 100 and 25 - 50
kg/ha K20 were the agronomic and economic rates of K application, respectively. Higher K
levels were needed in the field experiment while lower levels were needed in the greenhouse
experiment. These rates resulted in superior plant growth (stem diameter, height and leaf
expansion) and yield (number and weight of fresh leaves). Higher nutrient use efficiencies
were obtained on Kerugoya than on Mumias soils per kilogram of K applied. The quality of
Kale followed similar trends like the yields. There was an increase in leaf size with K
application. Mineral nutrient contents of elements such as K, Ca and Mg also increased in the
roots, stems and leaves with optimum amounts being obtained at 75 kg ha-1 K20 in the
Kerugoya field experiment.
Economic analysis showed that the optimum profit was obtained at application of 25 and 50
kg ha-1 K20 on the Kerugoya and Mumias soils in the greenhouse experiments and at the
Kerugoya field experiment, respectively. These fertilizer levels were lower than the optimum
yield levels implying that at the present fertilizer and kale prices it pays very little to use the
K fertilizer and cheaper sources of K should be considered | en |
