Danuta T. Knabe

Bio: Danuta T. Knabe is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 43 citations.

A comparison of methods to determine the onset of the growing season in northern Nigeria

Abstract: In the sudan savanna of northern Nigeria, with its semi-arid climate, the ability to determine effectively or predict the start of actual productive rains cannot be overemphasized. Several methods exist for calculating the date of onset of the rains that may be taken as the start of the growing season. Five methods currently in use, which are relatively easy to apply on a large scale, were selected for comparison. One is a traditional technique (Ramadan method), two use accumulated rainfall totals (Walter’s and Sivakumar’s methods), and two use rainfall–evapotranspiration relationships (Kowal’s and Benoit’s methods). For the period 1961–91, the traditional technique performed most poorly. Walter’s method gave quite early onsets and Sivakumar’s method gave very late onsets, thereby seriously shortening the growing season. Kowal’s and Benoit’s determinations fell most often in between the results of Walter’s and Sivakumar’s methods in their performance. However, although generally to a lesser extent than the other methods, they are still significantly affected by false starts. To avoid incorrectly predicting the growing season’s onset as far as possible, but to prevent an unacceptable shortening of the growing season, a combination of Kowal’s and Sivakumar’s criteria was used to develop an improved technique. This proved to work well for determining the onset date in the study area. However, because some false starts remain when using average onset dates, it is suggested that an operational advisory team should be constituted by the government. This team would be responsible for calculating onset dates in any year, on-line for the ongoing season, in a participatory approach with farmers, and for disseminating such dates to the farmers. This could be done for any place for which the appropriate data can be made available. In the future, improved climate prediction skill may replace the classical probabilistic approaches presently suffering from increasing rainfall variabilities. Copyright  2002 Royal Meteorological Society.

Termite damage and crop loss studies in Nigeria - a review of termite (Isoptera) damage to maize and estimation of damage, loss in yield and termite (Microtermes) abundance at Mokwa.

Abstract: Abundance of termites, damage to plants and loss in yield were studied on recently-cultivated and long-cultivated fields at Mokwa in the southern Guinea savannah zone of Nigeria. Virtually all damage was caused by Microtermes which have deep, diffuse subterranean nests and attack maize by entering the roots or prop-roots and may eventually extend their foraging by excavating the stem to heights varying from a few centimetres to over a metre. Attack on the roots commences at 10 to 12 weeks after planting and intensifies as the plants mature. Attacked plants may remain standing or fall over (lodged). Yield of grain on standing attacked plants was not significantly different from yield on standing unattacked plants. Cobs of lodged plants were damaged on the ground by termites, ants, rodents and pathogens and yield of grain was significantly lower than on standing plants. Yield losses on recently-cultivated fields (1–3 years) varied from 0.1 to 3.0% and on long-cultivated fields (10–27 years) from 3....

Effects of plant density of intercropped soybean with tall sorghum on competitive ability of soybean and economic yield at Otobi, Benue State, Nigeria

Abstract: Field experiment was conducted for three years to evaluate the influence of plant population density of intercropped soybean with sorghum on its competitive ability and economic yield at Otobi, Benue State, Nigeria. The experiment was laid out in split-split plot with three replications. The main plot treatment comprised of cropping systems with two levels (sole cropping, intercropping), while the sub-plot treatment was soybean variety at three levels (TGX 536-O2D, Samsoy 2, TGX 923-2E) and the sub-sub-plot treatment was plant population density of soybean at three levels (200,000 plants/ha; 333,000 plants/ha and 400,000 plants/ha). Planting intercropped soybean at 333,000 plants/ha gave significantly higher seed yield than planting at 400,000 plants/ha, which in turn had greater seed yield than planting at 200,000 plants/ha during the three years of experimentation. Increased density of soybean beyond 333,000 plants/ha in the intercrop reduced sorghum yield. The results showed that all the intercrop combinations had land equivalent ratio (LER) and area- time equivalency ratio( ATER) above unity (1.63 - 1.97) and (1.41 - 1.47),respectively, under all the densities of soybean tested, suggesting a considerable benefit for intercropping soybean with sorghum. LER figures decreased with increase in soybean density. ATER was highest at 333.000 plants/ha, suggesting higher productivity at this density. Aggressivity values were consistently negative at 200,000 plants/ha with a mean value of -0.25 and it was inconsistent at 333,000plants/ha and 400,000 plants/ha. The competitive ratio of soybean increased (0.76 - 1.15) with increasing density of the soybean in the intercrop combinations, indicating higher competitiveness at higher densities than the sorghum component. The competitive ratio of sorghum had the opposite response (1.23 - 0.76). Relative crowding coefficient (K) was inconsistent at all densities, while land equivalent coefficient (LEC) was above 0.25 indicating intercrop advantages for all combinations. ‘Soybean yield equivalent’ was also highest at 333,000 plants/ha (1.70) implying general suitability of soybean to intercropping at this density. Dominance analysis revealed that sole crop treatments were dominated. Intercropped soybean planted at 333,000 plants/ha and 400,000 plants/ha gave significantly higher net benefits than those planted at 200,000 plants/ha. Marginal analysis showed that planting soybean at 333,000 plants/ha gave the highest marginal rate of return and this was 2825%.These results suggest that growing soybean under intercropping at Otobi is biologically efficient at 333,000 plants/ha and more profitable. Key words: Intercropped soybean, density, competition, Otobi.

Epidemiology of hepatitis b infection among pregnant women in minna, nigeria

Abstract: A descriptive cross sectional study was conducted amongst 261 pregnant women attending ante natal clinic at General hospital, Minna, Nigeria to determine the social characteristics and seroprevalence of Hepatitis B Virus (HBV). The mean age of the respondents was 25years. Thirty two (12.3%) of the 261 blood samples tested positive for HBV. Of the the +ve cases, 13.6% were in the second trimester of their pregnancy and 60% within the age brackets of 21-30 years. Illiterate women constituted 15.9% of those sampled while civil servants were 13.6%. Testing for HBsAg is recommended for all pregnant women at first prenatal visit so that positive mothers receive prompt intervention.