Brown leaf spot disease and fertilizer interaction in irrigated rice growing on different soil types
Studies have been undertaken in a 1000 ha area of irrigated rice (Oryzica sativa) at Caroni (1975) Limited to determine the effect of the fertilizer programme on the incidence of important diseases. Over a period of three years higher levels of brown leaf spot (Cochliobolus miyabeanus) on rice varieties Oryzica 1 and Oryzica 5 on three different soil types were associated with increasing levels of leaf P, from a low of 0.149% of dry matter (DM) to a high of 0.396% DM. On the Washington silty clay loam series (Inceptisol) brown leaf spot incidence was lowest when leaf P was between 0.135% and 0.149% of DM. However, disease incidence was higher when leaf P levels fell to 0.133% of DM or rose above 0.149%, under conditions where N was more than adequate. The moderate levels of the disease experienced over the period had no effect on yield, as grain infection was minimal. The results support the conclusion that the incidence of brown leaf spot on irrigated rice at Caroni is influenced by sub-optimal levels paticularly of P. Careful monitoring and managememt of P nutrition is seen as an important part in the overall strategy for controlling the disease.
Effect of calcium silicate on blast and brown spot intensities and yields of rice.
Rice production in the subtropical climate of Florida is on Histosols, which are high in organic matter content and low in plant-available silicon (SI). broadcast rates of calcium silicate slag were 0, 5, 10, and 15 Mg/ha in 1987 and 1988. In 1987, applications of calcium silicate slag reduced blast by 30.5% and brown spot by 15.0% over the control. In 1988, blast and brown spot were reduced by 17.4 and 32.4%, respectively, over the control (...)
Serum Profiles of Luteinizing Hormone, Oestradiol and Cholesterol and Ovarian Functions in Layer Poultry Birds (Gallus domesticus) Fed Diets Containing Furazolidone
This study was carried out to assess the serum profiles of luteinizing hormone (LH), oestradiol, cholesterol and ovarian functions in layer poultry birds (Rhode Island Red;Gallus domesticus) fed a diet containing various concentrations of furazolidone (FZ). A total of 40 birds were randomly assigned to receive FZ 0, 200, 400 or 800 mg/kg feed (ppm) daily during the pre-laying age, i.e. 13–18 weeks (for 5 weeks). Blood samples were collected at weekly intervals. Concentrations of LH and oestradiol in serum were estimated at alternate weeks using radioimmunoassays. Serum cholesterol levels were analysed by an enzymatic calorimetric method. Furazolidone administration was terminated at the 18th week of age. The birds were sacrificed at 22nd week of age and ovarian tissues were processed for morphometric studies. Serum LH, oestradiol and cholesterol levels were affected by age (p<0.001) and FZ dose (p<0.001). Serum LH and oestradiol levels were lower (p<0.05) in birds receiving FZ 800 mg/kg feed daily compared with the controls, whereas serum cholesterol profiles were lower (p<0.05) in all FZ-administered groups than in the control group. The mean weight of ovaries having no yolky follicles observed in the group receiving FZ 400 or 800 mg/kg feed per day was reduced (p<0.05) compared with the control group. Dosing FZ at 800 mg/kg feed per day reduced (p<0.05) the mean volume of ovaries having no yolky follicles compared with the control group. In birds receiving FZ 800 mg/kg feed per day, the mean length of the oviduct was reduced (p<0.05) as compared with the control group. Morphometric studies revealed that the mean number of oocytes with diameter in the range 401–800 μm decreased (p<0.05) in birds fed FZ 400 or 800 mg/kg feed per day. Initial egg production was affected by age (p<0.001) and dose (p<0.001) of FZ. The mean number of eggs laid by different groups revealed that egg production was reduced (p<0.05) in birds receiving FZ 800 mg/kg feed per day as compared with the controls. The present data suggest that FZ causes suppression in serum profiles of LH, oestradiol, cholesterol and ovarian functions in Rhode Island Red layer poultry birds. Therefore, great care must be taken with use of FZ in layer poultry birds (Gallus domesticus) with regard to dosage and duration of administration.