Yields of Green Grams and Pigeonpeas under Smallholder Conditions in Machakos County,Kenya

Green grams and pigeonpeas have multiple benefits to the rural poor as food security, fodder for livestock and fuel for small-scale farmers, despite low smallholder yields in Kenya. However, little is known about the factors between different farmers that influence the yields of green grams and pigeonpeas. The objectives of this study therefore were to describe and compare how the groups of farmers in agro-ecological zones (AEZs) LM 4 and LM 5 differ by their yields of green grams and pigeonpeas and to estimate the parameters of the variables which explain the yields. Data collection was through a well-structured questionnaire, administered to 364 respondents, selected through a multi-stage sampling technique. Each AEZ had an equal sample size (182 respondents). One-way analysis of variance (ANOVA) and multiple linear regression were used during data analysis. The ANOVA results showed that the mean of the green gram yields in AEZs LM 4 and LM 5 was 19.90 and 173.67 kg ha^?1 while the mean of the pigeonpea yields was 109.26 and 34.01 kg ha^?1, respectively. The multiple linear regression model results showed that the green gram yields were positively related to the use of improved seed (p?=?0.001), cultivated farm sizes (p?=?0.011), green gram crop intensity (p?=?0.005), oxcart (p?=?0.003) and agro-ecological zone (p?=?0.000). The farmer differences in the use of improved seed were found to be significantly and positively related to the yields of pigeonpeas (p?=?0.057), while the sizes of the cultivated farms (p?=?0.057) and the agro-ecological zones (p?=?0.000) showed inverse relationships (IRs). Based on the given research evidence, it was therefore concluded that the groups of farmers in AEZs LM 4 and LM 5 have different yields of green grams and pigeonpeas and there are factor gaps in productivity.     

Studies in the Development of the Strawberry: III. Flower-Bud Initiation and Development in Large-Fruited Perpetual (“Remontant”) Strawberries

Summary

Four N application rates generated a range of tree N status as indicated by leaf N concentrations in six year old trees of `Mission' almond (Prunus dulcis (Mill.) D. A. Webb). Leaf N concentrations were related positively with concentrations of amino acids - especially asparagine and glutamine - in phloem and xylem saps. A pulse of 1.25 kg N per tree was applied to trees previously receiving 0, 78, 157 or 313 g N per tree, annually. Apparent uptake of soil N into above-ground tree parts was determined over a 39 d period. N uptake was determined as the difference in the products of tree biomass and tissue N concentrations before and after the N pulse. Tissue N concentrations increased signi®cantly in trees previously receiving the two lowest N application rates, whereas trees previously receiving the high N treatments were unresponsive. Tree N contents (0 g N per year, and also 78 g N per year treatments) increased slightly in response to the N pulse, although statistical differences were not observed due possibly to high variability in biomass among trees. At the same time, the amino acid concentrations in phloem exudate and xylem sap were highest in trees grown under the highest N fertilization regime. We suggest that the high amino acid concentrations in the phloem and xylem saps are indicative of a larger pool of amino N cycling throughout the vasculature of high N-status trees. Our data indicate an inverse relationship between tree N status, amino acid concentrations in xylem and phloem saps and capacity for soil N uptake in ®eld-grown trees. These results represent the ®rst ®eld data to correlate the concentration of amino acids circulating in the plant vasculature with soil N uptake. A functional relationship between the amino acid concentrations cycling within the tree and the regulation of soil N uptake has, however, not yet been established.     

Studies in the Development of the Strawberry: II. Stolon Production by First-Year Plants in 1952

Studies were carried out on the assumption that incompatibility and dwarfness of budded citrus trees result from impaired carbohydrate movement through the bud union. During autumn and winter, carbohydrates move from the tree tops to the roots and accumulate there as starch. The starch level can therefore serve as a measure of this movement.

This study included seven rootstock varieties all budded with Shamouti orange scion. Unbudded rootstocks were included for purposes of comparison.

The starch level was determined in the winter at three locations along the trunk, below and above the bud union.

No clear indication was found of impaired carbohydrate movement through the bud union of stock-scion combinations showing very low growth vigour.

The starch level in bark and wood in the rootstock portion of trunks of budded trees was found to be negatively correlated with tree size. This indicates that the level of starch in the trunk results from the growth vigour of the tree and is not a factor which affects it.

No relation was found between starch level in the scion and tree size. Based on these findings the conclusion was reached that incompatibility and low growth vigour in citrus do not seem to result from impaired carbohydrate movement through the trunk and starvation of the roots.     

Understory plant species and functional diversity in the degraded wet tropical forests of Kolombangara Island,Solomon Islands

Anthropogenic activities have resulted in extensive deforestation and forest degradation on many tropical oceanic islands. For instance, some islands in the Solomon archipelago have as little as 10% of primary forests remaining with few of these remnants protected from future land use change. We examine the plant species and functional diversity (excluding adult canopy trees) of 48 sites from four forest land use types (two types of primary forest, secondary forest and abandoned tree plantations) and two common human-maintained land use types (coconut plantations and grazed pastures) across three elevation bands on Kolombangara Island, Solomon Islands. In total, we surveyed 384 species from 86 families of which only 6.5% were non-native. Species richness was lowest in coconut plantations and grazed pastures and declined with increasing elevation across all land use types. Functional diversity was similar between primary and secondary forest (high richness, high evenness and unaltered dispersion) and lowest in coconut plantations and grazed pastures. Our results suggest that species and functional richness have had divergent responses to land use change in forest land uses indicative of a loss of functional redundancy. Despite structural and compositional similarities among primary forests and degraded forest land uses, full recovery of secondary and commercial plantations has not been achieved. We suggest that conservation of Kolombangara’s forest understory flora will require reserves across the island’s elevation gradient and may require active restoration in the future, particularly if degrading activities continue at the current rate.     

Verte and Romaine lettuce varieties (Lactuca sativa) show differential responses to high NaCl concentrations

In this study, we report on the relationship between individual antioxidant carotenoids, phenolic fractions, and flavonoids and attenuating NaCl toxicity in two contrasting varieties of lettuce (Lactuca sativa L., var. Verte and Romaine), as a means of developing more precise targets for lettuce breeding. In seedling leaves, carotenoid levels increased under NaCl stress in Verte, but remained unchanged in Romaine. Chlorogenic acid (CGA), a soluble polyphenol abundantly present in leaves, was the only phenolic acid that accumulated significantly in both varieties and was predominant under salinity. Remarkably, CGA was more prominent in Verte than Romaine at moderate salinity levels (100 mM). Foliar flavonoid levels were also differentially increased in both seedling types grown under 100 mM NaCl, but dropped significantly in both varieties under 200 mM NaCl. Germination, which was overall more salt‐resistant in Romaine, was significantly increased under salt stress by application of low dosage (10^–6 to10^–5 M) of CGA to Verte, but not to Romaine. These results suggest that CGA is involved in modulating NaCl‐induced oxidative‐stress responses during seed germination in Verte.     

Comparison of bacterial culture, polymerase chain reaction, and a mix-enzyme-linked immunosorbent assay for the detection of Salmonella status in grow-to-finish pigs in western Canada with a Bayesian approach

Among grow-to-finish pigs from 10 herds in Alberta and Saskatchewan, 23 (16%) of 144 fecal samples were culture-positive and 40 (28%) of 144 pigs were seropositive for Salmonella. With a Bayesian model specifying dependence between the 2 tests, the sensitivity (Se) of culture and real-time polymerase chain reaction (RT-PCR) was 79% to 86%, depending on the cut-off value for the enzyme-linked immunosorbent assay (ELISA). Culture specificity (Sp) was assumed to be 100%; RT-PCR Sp was found to be 94%. The ELISA Se was 76% and 51% at optical density cut-off values ≥ 20% and ≥ 40%, respectively; the Sp was 94% at each cut-off value. The model showed some sensitivity to ELISA prior information, the ELISA Se being approximately 8% lower when informative prior information was specified in the model. When there was no adjustment for dependence between culture and RT-PCR, the posterior estimates for both culture and RT-PCR Se were 11% higher than with the conditional-dependence model and had considerably narrower probability intervals, which suggests that correlation between culture and PCR is important and should be adjusted for in future studies.