Showing papers by "College of Tropical Agriculture and Human Resources published in 1990"

Interaction of Ca(H2PO4)2 applied to an Oxisol and previous sludge amendment: soil and crop response.

Abstract: Treble superphosphate (TSP) was applied at 0 and 120 kg P/ha to a highly weathered Oxisol which had received various levels of a sewage sludge 5 years earlier. Lettuce (Lactuca sativa L.) was grown as a test crop. Plant and soil chemical composition indicated that the efficiency of TSP was significantly increased in the presence of sludge: 120 kg P/ha added to soils amended with 45, 90, and 180 Mg/ha sludge were correspondingly as effective as 306, 314, and 196 kg P/ha as TSP required by the unamended soils. This is probably because organic anions and molecules produced by the sludge reacted with P fixing sites on the soil surface and/or chelated‐precipitated soluble Al. Furthermore, increased Ca levels in soil solution by sludge or TSP addition improved plant growth and reduced Al uptake. For lettuce, the adequate Ca range was 400–500 mg/L in soil solution and 1.9–2.0% in leaf. Because of an unexpected additional input, adequate range of soil solution P could not be clearly determined for lettuc...

Sulfur status of volcanic ash‐derived soils in Hawaii

Abstract: Several rainwater samples and 14 profiles of Hawaii's volcanic ash‐derived soils were analyzed for sulfur (S). Atmospheric deposition was an important S source at the coast (24 kg S/ha), but its contribution decreased with increasing distance from the sea (1 kg S/ha at 24‐km inland). The S concentration of rainwaters also decreased linearly with increasing rainfall. Several thousand mg SO4‐S/kg can be extracted from many volcanic ash‐derived soils of Hawaii, and it was often required at least four extractions [0.04 M Ca(H2PO4)2, 1:10 soil to solution ratio] to completely desorb this SO4. There was a close association of high SO4 retention with high rainfall. This might have resulted from (1) the development of a solid phase with high SO4 retention under intense weathering conditions, (2) more total SO4 received by the soils from atmospheric deposition, and (3) past fertilization of sugarcane grown in high rainfall areas. Low concentrations of soil solution SO4‐S in relation to large amounts of P‐...

Field movement and persistence of fenamiphos in drip‐irrigated pineapple soils

Abstract: The persistence and mobility of fenamiphos and its toxic oxidation products in soil with pineapple cropping were studied in three field experiments on the islands of Oahu and Lanai, and by sampling three commercial fields on Oahu. Fenamiphos was applied by drip irrigation after planting, following pre-plant application of 1,3-dichloropropene (1,3-D) in most treatments. The Oahu experiments, conducted on highly weathered Oxisol and Ultisol soils, evaluated the impact of restricted irrigation to reduce leaching and also the effect of 1,3-D on fenamiphos behavior. Total toxic residue (TTR) concentrations of 1000 ug kg−1 or greater were maintained in the root-zone with fenamiphos applications of 3.4 kg ha−1 tri-monthly on the Oxisol (Kunia site) and bi-monthly on the Ultisol (Whitmore site). The relatively high applications, along with weekly irrigations and unseasonably high rainfall, resulted in leaching of fenamiphos TTR out of the root-zone with concentrations between 10 and 100 ug kg−1 at 3 m depth. Reduced leaching with restricted irrigation was evident in the early months of both Oahu experiments. The potential to minimize leaching of fenamiphos by reduced application rates and limited irrigation during rainy periods was evident from nematicide concentration profiles measured on three commercial pineapple fields on Oahu; little fenamiphos TTR was detectable below 1 m.

Reduced pesticide use in an IPM program for anthuriums.

Abstract: An integrated pest management program (IPM) for anthuriums successfully reduced pesticide applications without reducing production and marketability. During 1986 and 1987, insecticide, acaricide, and fungicide applications at three farms studied were reduced by 45, 79, and 96%, respectively, by economically justifying spray applications. No significant increase in thrips, mite, or anthracnose injuries occurred, nor did total cost for treatment and pest damage increase. Our study indicated that the IPM concept implemented on a floricultural crop can reduce pesticide applications and increase profitability.

Formation of mutagens during the frying of Hawaiian fish: correlation with creatine and creatinine content.

Abstract: Compounds mutagenic toward Salmonella typhimurium strain TA98 in the presence of rat-liver homogenates (S9) were formed when fish flesh was fried at 199° C. Three species of Hawaiian fish commonly consumed in Hawaii (skipjack tuna, Katsuwonus pelamis ; yellowfin tuna, Neothunnus macropterus ; and milkfish, Chanos chanos ) were cooked in an electric skillet, along with samples of sole ( Microstomus pacificus ). Organic extracts of the fish were tested in the Ames Salmonella mutagenic assay using tester strain TA98 and S9. Basic organic extracts of fried, but not raw, samples exhibited significant mutagenicity. The levels of mutagenicity were also higher among the red flesh Hawaiian fish ('ahi, aku and awa) than with the white flesh sole. Creatine and creatinine contents were highest in the Hawaiian fish and lower in the sole. Creatine levels in the fish were 50–100 times greater than the creatinine content and varied from a high of 645 mg/100 g wet weight of fish for yellowfin tuna to a low value of 251 mg/100 g for sole. Mutagen levels are only approximately related to creatine/creatinine levels suggesting that other components contained in these fish may be as important as the guanidines in determining the levels of mutagen in the cooked fish.

The Relationship of Siblings to the Size of Rural Nigerian Preschoolers

Abstract: Staff from a health education project in Eket village in Cross River State Nigeria collected 1985-1986 height and weight data from at least 286 preschool children. Results from the 1 way analysis of variance tests revealed that age significantly affected mean weights for age and for height (p<.01). For example between 1 and 2 years of age the weights for age and for height fell substantially due to a decrease in breast feeding and introduction of solid foods. Similarly birth rank significantly accounted for mean height for age (p=.01) and mean weight for age (p<.01). For instance the mean height for age and mean weight for age fell for 2nd born children. After the 2nd child they climbed to the point where at the 6th child and greater the means were greater than for the 1st born. Number of children in the household only significantly affected mean weight for age (p=.01). A single child ranked significantly better in weight for age and weight for height than households with 2-6 children. After the 3rd child however a steady increase in mean percentile rank occurred with each additional child. In fact mean percentile weight for age values of all the children in households of 7 or more children were higher than for any other household size. Observations of field staff supported the hypothesis that in large families the older children care and nurture the younger siblings and do not have high demands to work in the fields and maintain the households thereby accounting for the superior nutritional status for children in families of 7 or more children. Nevertheless overall nutritional status of 28% of the children were severely malnourished. Further current nutritional status of 14% were severely malnourished. Moreover 36% ranked as chronically malnourished.