The use of symbiotic azolla-caroliniana as a water management technique in paddy fields: a case study of lower Moshi irrigation project in Tanzania.
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Date
2002
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
Traditional water management techniques employed in irrigated rice production are
deficient, particularly in controlling moisture loss. In this study, Azolla caroliniana
backed by conventional approaches (e.g soil puddling, sub-soil compaction and levee
coating reinforced with lateral flow barriers) was used to suppress evapotranspiration
in rice Helds under irrigation. A field experiment was carried out at Lower Moshi
irrigation project in Kilimanjaro region in Tanzania between the dry season and short
rainy season from September 2000 to January 2001. The study was done at the
Kilimanjaro Agricultural Training Centre (KATC) experimental farm, which has
medium clay soils. The aim was to evaluate the effect of Azolla caroliniana (a green
manure with symbiont blue green algae) in economising irrigation water in rice
cultivation. The type of rice used in the study was a local indigenous variety known
as Wahiwahi. The water balances for the growing period and grain yields at harvest
were determined. Yield attributes were assessed for the effect of Azolla. The
experiment was conducted in a randomized complete-block design with four
replications and three treatments. The plot sizes were each 5.3 m x 5.1 m. The
treatments were: Wahiwahi only (Tl); Wahiwahi and Azolla (T2) and Azolla only
(T3). Ridges were made around the individual plots to allow ponding. A nursery for
pre-germinated rice seeds was established for 25 days after which the seedlings were
transplanted. Azolla was administered in treatments T2 and T3, 7 days after
transplanting. Crop water use measurements were done at 14 days post transplanting
and thereafter daily for the whole growing period (three and half months). Parameters
monitored in total water use were evapotranspiration and seepage and percolation.
One lysimeter and one percolation cylinder were installed in each treatment to
facilitate the measurements. Other data collected included measuring plant growth
(plant height, straw dry weight, number of tillers, heading time and weed population);
determining yield components (number of panicles and grains, percent of ripe grains
and grain weight at harvest) and grain yield. The total water use obtained in
treatments T2 and T3 were 8.13 mm/day and 7.05 mm/day respectively, which were
not significantly different (p < 0.05). In treatment Tl, the total water use observed
was 11.99 mm/day, which was significantly higher (p < 0.05) than T2 and T3. There
was no significant effect (p < 0.05) of Azolla on seepage and percolation. Tlxe lowest
evapotranspiration was obtained in treatment T3 with 2.24 mnv'day, wliich was
significantly different (p < 0.05) from T1 and T2. Evapotranspiration was 6.48
mm/day in treatment T2 which was 23% lower and significantly dififerent (p、0.05)
fiom that in Tl. Reduced dry matter weiglit of weeds was registered in T2 and T3
where the weed control efficiency was significantly higlier (p < 0.05) tlian Tl. Rice
plant growth in T2 was greater and more superior throughout the growing period
compared to plants in Tl. The grain yield in T2 was 7.93 t/ha which was significantly
higher (p < 0.05) than 6.31 t/ha in Tl. Azolla management e俭ct gave soil-moisture
retentivity of 32% that resulted in increased water use efficiency by tlie crop. The
crop stand was improved and grain yield increased. The use of Azolla caroliniana in
irrigated rice cultivation is recommended as a water management practice.
Description
Dissertation
Keywords
Moshi irrigation project, Evapotranspiration, Azolla production, Evaporation