On-farm productivity of Acacia angustissima, Calliandra calothyrsus and Leucaena leucocephala in a subhumid area in Zimbabwe

Smallholder dairy farmers in Natural Region II, especially in Chikwaka Communal Area, adopted Acacia angustissima, Calliandra calothyrsus and Leucaena leucocephala in the 1995/96 season as alternatives for supplementing expensive commercial dairy feeds. Although several on-station trials have been done in the subhumid region of Zimbabwe,  there have been no studies assessing on-farm yields of the introduced fodder species. This study evaluated productivity in a communal area under varying soil (pH, nitrogen, phosphorus and potassium) and  management conditions (protection and tree density). Leaf  productivity was high on farms with relatively higher soil P. Leaf yields  ranged from 0.4–3.3 t DM ha–1 for A. angustissima, 0.8–5.6 t DM ha–1 for C. calothyrsus and 0.2–0.7 t DM ha–1 for L. leucocephala Acacia angustissima, Calliandra calothyrsus and Leucaena leucocephala in the 1995/96 season as alternatives for supplementing expensive commercial dairy feeds. Although several on-station trials have been done in the subhumid region of Zimbabwe,  there have been no studies assessing on-farm yields of the introduced fodder species. This study evaluated productivity in a communal area under varying soil (pH, nitrogen, phosphorus and potassium) and  management conditions (protection and tree density). Leaf  productivity was high on farms with relatively higher soil P. Leaf yields  ranged from 0.4–3.3 t DM ha–1 for A. angustissima, 0.8–5.6 t DM ha–1  for C. calothyrsus and 0.2–0.7 t DM ha–1 for L. leucocephala Acacia angustissima, Calliandra calothyrsus  and Leucaena leucocephala in the 1995/96 season as alternatives for supplementing expensive commercial dairy feeds. Although several on-station trials have been done in the subhumid region of Zimbabwe,  there have been no studies assessing on-farm yields of the introduced fodder species. This study evaluated productivity in a communal area under varying soil (pH, nitrogen, phosphorus and potassium) and  management conditions (protection and tree density). Leaf  productivity was high on farms with relatively higher soil P. Leaf yields  ranged from 0.4–3.3 t DM ha–1 for A. angustissima, 0.8–5.6 t DM ha–1 for C. calothyrsus and 0.2–0.7 t DM ha–1 for L. leucocephalawith mean values of 2.2, 2.6 and 0.4 t DM ha–1, respectively. The low yields  of L. leucocephala were associated with psyllid (Heteropsylla cubana) infestation. Decrease in tree density (low population) resulted in reduced yield. Poor performance was also attributed to uncontrolled browsing. Influence of soil characteristics could not be confirmed, but  there were indications that low soil phosphorus may have adversely affected tree growth. The yields were generally lower than on-station, which implies that there is room for improving fodder tree yields in this subhumid region, through improving the availability of P, planting a high density of trees, and protecting them from uncontrolled browsing.African Journal of Range & Forage Science 2009, 26(2): 75–8

Paclobutrazol retards vegetative growth in hydroponically-cultured Leonotis leonurus (L.) R.Br. Lamiaceae for a multipurpose flowering potted plant

Leonotis leonurus (L.) R. Br. Lamiaceae, commonly known as wild dagga or lion's ear, is a robust ornamental shrub with multiple medicinal uses. It grows widely throughout South Africa, especially amongst rocks in grasslands (Agnihotri et al., 2009). L. leonurus has bright orange nectar-rich velvety flowers, which are displayed in whorls at the top of each stem (Riley, 1963; Joffe, 2003). This fast growing perennial is drought tolerant and contains long soft and hairy leaves with serrate edges. Amongst its multiple uses are several medicinal applications, such as treatment for snake, spider and scorpion bites as well as bee stings (Ascensão et al., 1995). An infusion and a decoction of the leaf and stem have been used internally for coughs, colds, influenza, bronchitis, high blood pressure and headaches (Bienvenu et al., 2002). In addition, it has traditionally been smoked for the relief of epilepsy. L. leonurus is a very beautiful garden ornamental, with great potential as a flowering potted plant. Despite its great potential as a potted flowering plant, it often grows up to 3 m tall and 1.5 m wide, thus making it difficult to grow as a potted flowering plant

Spectral analysis software improves confidence in plant and soil water stable isotope analyses performed by isotope ratio infrared spectroscopy (IRIS). Rapid Commun Mass Spectrom 2011

Previous studies have demonstrated the potential for large errors to occur when analyzing waters containing organic contaminants using isotope ratio infrared spectroscopy (IRIS). In an attempt to address this problem, IRIS manufacturers now provide post-processing spectral analysis software capable of identifying samples with the types of spectral interference that compromises their stable isotope analysis. Here we report two independent tests of this post-processing spectral analysis software on two IRIS systems, OA-ICOS (Los Gatos Research Inc.) and WS-CRDS (Picarro Inc.). Following a similar methodology to a previous study, we cryogenically extracted plant leaf water and soil water and measured the d H and d 18 O values of identical samples by isotope ratio mass spectrometry (IRMS) and IRIS. As an additional test, we analyzed plant stem waters and tap waters by IRMS and IRIS in an independent laboratory. For all tests we assumed that the IRMS value represented the "true" value against which we could compare the stable isotope results from the IRIS methods. Samples showing significant deviations from the IRMS value (>2s) were considered to be contaminated and representative of spectral interference in the IRIS measurement. Over the two studies, 83% of plant species were considered contaminated on OA-ICOS and 58% on WS-CRDS. Post-analysis, spectra were analyzed using the manufacturer's spectral analysis software, in order to see if the software correctly identified contaminated samples. In our tests the software performed well, identifying all the samples with major errors. However, some false negatives indicate that user evaluation and testing of the software are necessary. Repeat sampling of plants showed considerable variation in the discrepancies between IRIS and IRMS. As such, we recommend that spectral analysis of IRIS data must be incorporated into standard post-processing routines. Furthermore, we suggest that the results from spectral analysis be included when reporting stable isotope data from IRIS

Phragmites australis: How do genotypes of different phylogeographic origins differ from their invasive genotypes in growth, nitrogen allocation and gas exchange?

It has been suggested that in plant invasions, species may develop intrinsically higher gas exchange and growth rates, and greater nitrogen uptake and allocation to shoots, in their invasive range than in their native habitat under excess nutrients. In this study, native populations of two old world Phragmitesaustralis phylogeographic groups (EU and MED) were compared with their invasive populations in North America [NAint (M) and NAint (Delta)] under unlimited nutrient availability and identical environmental conditions in a common garden. We expected that both introduced groups would have higher growth, nitrogen uptake and allocation, and gas exchange rates than their native groups, but that these enhanced traits would have evolved in different ways in the two introduced ranges, because of different evolutionary histories. Biomass, leaf area, leaf nitrogen concentrations (NH4+ and NO3−) and transpiration rates increased in introduced versus native groups, whereas differences in SLA, leaf pigment concentrations and assimilation rates were due to phylogeographic origins. Despite intrinsic differences in the allocation of C and N in leaves, shoots and rhizome due to phylogeographic origin, the introduced groups invested more biomass in above-ground tissues than roots and rhizomes. Our results support the concept that invasive populations develop enhanced morphological, physiological and biomass traits in their new ranges that may assist their competiveness under nutrient-enriched conditions, however the ecophysiological processes leading to these changes can be different and depend on the evolutionary history of the genotypes