PD/A CRSP Eighteenth Annual Administrative Report
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Subcontract No. RD010A-07
Auburn University, Alabama
|Wesley Wood||US Principal Investigator, Project Leader|
Sagana Fish Farm, Sagana, Kenya
|Bernard Meso||Graduate Assistant, University of Nairobi (CRSP funded)|
University of Nairobi, Kenya
|Nancy Karanja||Host Country Co-Principal Investigator|
|S.M. Kinyali||Host Country Co-Principal Investigator (through January 2000)|
Integration of aquaculture and agriculture systems can result in higher productivity of each component. In Kenya fish are grown in both irrigation reservoirs and fish ponds. Farmers may be reluctant to fertilize irrigation water due to a lack of information on the effects of fertilization on irrigated crops. On the other hand, water from fish ponds may be used to irrigate agricultural crops. One goal of the Government of Kenya is to encourage multiple uses of irrigation waters. This investigation was designed to assess the effects of fertilizing irrigation water and of using fishpond effluent to water crops.
The following Ninth Work Plan investigation continued into the current reporting period:
Note: The methods for 9ER1 have been modified. The revised methods will appear in the Addendum to the Ninth Work Plan. This study is a collaboration among Auburn University (AU), Oregon State University (under MOU No. RD009A), and AU (under Subcontract No. RD010A-08).
CRSP Effluents and Pollution researchers have hosted over 100 visitors to the Sagana site, including representatives from the Kenyan government's Arid and Semi-Arid Lands (ASAL) project in Laikipia, Kenya. Visitors representing the Ministry of Agriculture have also requested that the researchers continue their drip irrigation work as a demonstration plot for local farmers.
Wood is now an adjunct graduate faculty member at the University of Nairobi, Kenya.
Meso, B. Application of fish pond effluent to French
beans through drip irrigation at Sagana, Kenya. Presented
to the Soil Science Society of East Africa (SSSEA)
Silver Jubilee (25th Annual) Conference at Kampala,
Uganda, 610 September 1999.
Wood, C.W. and C.E. Boyd. Carbon and nitrogen in pond bottom soils. Presented to World Aquaculture 2000 at Nice, France, 26 May 2000.
The Soil Science Society of East Africa (SSSEA) Silver
Jubilee (25th Annual) Conference at Kampala,
Uganda, 610 September 1999. (Meso)
World Aquaculture 2000 at Nice, France, 26 May 2000. (Wood)
Bernard Meso was awarded the prize for academic excellence and diversity in soil science at university post-graduate level from the Soil Science Society of East Africa (SSSEA) Silver Jubilee (25th Annual) Conference at Kampala, Uganda, 610 September 1999.
Wood was named a Fellow of the Soil Science Society of America.
When fish are recovered from ponds, the effluent is
often drained, presenting both an environmental challenge and
an agricultural opportunity. The effects of irrigation with
pond effluent and its interaction with applied fertilizer
were assessed in a field experiment using French bean
(Phaseolus vulgaris) and kale (Brassica
oleracea) over two growing seasons near Sagana, Kenya. Fresh and dry matter yields
of the crops were recorded at harvest, and samples
were collected for determination of tissue nutrient
concentration. In the first season, French bean fresh pod yield
differed significantly (P = 0.05) among treatments. Plots
canal water and fertilizer at recommended rates had
the highest yield (9.1 t fresh pod ha-1), while those receiving
no fertilizer or irrigation had the lowest yield (1.3 t fresh pod
ha-1). In the second season, significant differences
(P = 0.05) were observed among treatments in fresh bean pod and fresh
kale leaf yields. The highest (4.4 t
ha-1) fresh pod yield was observed in pond-effluent-irrigated and fertilized
plots, while the lowest (1.3 t ha-1) was observed in
non-irrigated/unfertilized plots. The highest fresh kale leaf yield (11.5 t
ha-1) was obtained with irrigation with canal water
combined with fertilizer application, while the lowest (4.2 t
ha-1) was observed in non-irrigated/unfertilized plots. Low
nutrient status in the pond water together with inadequate
water supplied to some crops due to emitter clogging
was responsible for low yields in treatments where pond
water was substituted for canal water. Pond water from the
Sagana Fish Farm supplied low amounts of nitrogen (N)
and phosphorus (P) for crops, indicating that recommended
rates of mineral fertilizers should be used when pond water
is used for irrigation. In the second experiment, the
effectiveness of two types of soil occurring at Sagana,
Kenyaa vertisol (black clay soil) and a cambisol (red clay
soil)in retaining nutrients from pond effluent was investigated.
A laboratory experiment was conducted with soil
columns containing red or black clay soil. Pond effluent
application intensities of 31, 81, and 161 mm
d-1 were tested on both soils. Both soils retained over 60% of total P from
pond effluents, with red clay soil retaining 27% more P than
black clay soil. At the high effluent loading rate, low % N
removal was observed in both soils. Total N removal
efficiency declined with time after 21 days at the high rate, and
after that time no N removal was observed where red clay
soil was used. Black clay soil was more enriched by N than
red clay soil, while P enrichment was higher in red clay soil
than in black clay soil. It appears that land application
can remove substantial amounts of P and N from pond effluent.
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