Nutrient changes in potting mix and Eucalyptus nitens leaf tissue under macadamia biochar amendments

The effect of macadamia nut shell biochar on nitrogen,potassium,phosphorus,magnesium,calcium and sodium concentrations in potting mix used to grow Eucalyptus nitens seedlings was investigated in a glasshouse experiment.The treatments combined two fertiliser rates(50 and 100% rate of the commercial mix commonly used in forestry nurseries) with eight biochar rates(0,2,5,10,20,50,80 and 100 t ha~(-1)) arranged in a randomised complete block with three replicates of four sample plants.Nutrients were quantified in the potting mix and seedling leaves at four destructive harvests 135,177,219 and269 days after planting.Biochar significantly increased nitrate-N,Colwell P,Colwell K and exchangeable Na andreduced ammonium-N,Mg and Ca concentrations in the potting mix.Seedling leaf concentrations of P,K and Na were increased by biochar application,while N remained dependent on fertiliser rate only.Mg and Ca leaf concentrations decreased in response to increasing biochar rates.Elevated nitrate-N and decreased ammonium-N concentrations suggest that biochar might have increased nitrification in the potting mix.We presumed that biochar mediated processes that reduced uptake of P and K when high doses of biochar were combined with full fertilisation.Changes in potting mix K,Na,Mg and Ca were consistent with selective adsorption of ions to biochar surfaces.     

Crop productivity under differently lopped canopies of multipurpose trees in Central Himalaya, India

Ficus species are multipurpose trees well known by rural populations in Sahelian and Sudanian zones of Africa. Their uses are well documented but their amenability for vegetative propagation has not been extensively studied. This paper compares the rooting ability of stem and aerial root cuttings from thirteen Ficus species found in West Africa. It highlights the differences between species belonging to the sub-genera Sycomorus and Urostigma. The former show no capacity to propagate from cuttings whereas the latter, with epiphytic development, can be propagated by cuttings, although this capacity varies among species. Thus, F. thonningii, F. leprieurii and F. ovata are easily propagated, while F. platyphylla and F. elasticoides are propagated with difficulty. The rooting capacity also varies depending on the cutting material used. It decreases in the following order: long leafless hardwood cuttings (pole) > nodal cuttings > apical cuttings. Rooting potential increases when the cuttings are harvested towards the end of the dry season(March to May). Aerial root can be used for cuttings in all species of the sub-genus Urostigma. The capacity of root cuttings to regenerate is greatest when cuttings are collected at the beginning of the dry season (November). In this case, wound-induced adventitious roots arise at the basal end of the cutting while de novo buds are developed from the cambium at the distal end. The subsequent morphological development is identical to that of a stem cutting. These results clarify and allow the optimal use of the knowledge and methods developed by the indigenous people of the Sahel and could assist and promote fig tree (Ficus sp.) domestication in the dry tropics.This revised version was published online in November 2005 with corrections to the Cover Date.     

Bio-amelioration of alkali soils through agroforestry systems in central Indo-Gangetic plains of India

A long-term field study was initiated during 1995 at Central Soil Salinity Research Institute, Regional Research Station, Lucknow(26°47′58′′ N and 80°46′24′′ E) to analyze the effect of agroforestry systems on amelioration of alkali soils. Three agroforestry systems(pastoral, silvipastoral and silvicultural) were compared with the control where no agroforestry system was introduced. Tree-based silvicultural and silvipastoral systems were characterized by tree species Prosopis juliflora and Acacia nilotica along with grass species Leptochloa fusca, Panicum maximum, Trifolium alexandrium and Chloris gayana. Growth of ten-year-old Prosopis juliflora and Acacia nilotica planted in combination with grasses was significantly higher over the silviculture system with the same species. Tree biomass yields of P. juliflora(77.20 t?ha-1) and A. nilotica(63.20 t?ha-1) planted under silvipastoral system were significantly higher than the sole plantation of(64.50 t?ha-1 and 52.75 t?ha-1). Fodder yield under the pastoral system was significantly higher than the silvipastoral system during initial years but it was at par with that of silvipastoral systems after eight years of plantation. The microbial biomass carbon in the soils of silvipastoral systems was significantly higher than in soils under sole plantation of trees and control systems. The Prosopis-based silvipastoral system proved more effective in reducing soil pH, displacing Na+ from the exchange complex, increasing organic carbon and available N, P and K. Improvement in soil physical properties such as bulk density, porosity, soil moisture and infiltration rate was higher in the Prosopis-based silvipastoral system than in the silviculture system or control. On the basis of biomass production and improvement in soil health due to tree + grass systems, silvipastoral agroforestry system could be adopted for sustainable reclamation of highly alkali soils.     

Occurrence of aphid vector and genetic tolerance to infection by potyvirus in hot pepper

The productivity and marketable quality of hot pepper (Capsicum annuum var. annuum L.) are low in tropical regions mainly due to virus infections and lack of effective virus management strategies. The absence of effective virus management strategies could be attributed to lack of information on virus vectors and host resistance. Parental (P₁ and P₂) and progeny (F₁, B₁, B₂ and F₂) generations of five hot pepper crosses were grown in Ethiopia at three sites (Bako, Hawasa and Melkasa) to monitor number and species of potential aphid vectors, disease incidence levels with regards to natural infections by Potato virus Y (PVY) and Ethiopian pepper mottle virus (EPMV) complex, and to determine genetic tolerance of the crop to the viruses. Disease incidence was assessed before the flowering stage of the crop plants using visible disease symptoms due to infections by PVY and EPMV. The serological tests revealed presence of symptomless genotypes of the crop to the virus infections. Aphid species potentially transmitting the viruses, such as Acyrthosiphon pisum (Harris), Aphis fabae (Scopoli), and Myzus persicae (Sulzer), were identified from specimens caught by yellow water traps. The highest number of aphids from yellow water traps was recorded at a dense foliage growth stage of the crop at Melkasa. Highly significant variation was observed among generations of the five crosses in response to infections by PVY and EPMV complex. The most susceptible parents had the levels of disease incidences ranging from 80 to 90%, whereas their progenies had only below 30% incidence levels. The most tolerant parent remained symptomless to the natural infections of PVY- and EPMV-complex. Incidence levels in progenies of a cross from the most susceptible and tolerant parents remained below 20%. Based on serological test, the proportion of PVY-positive plants ranged from 0 to 75% and of EPMV-positive plants from 0 to 25%, with 0 to 17% co-infection by the two viruses. Availability of virus sources in the vicinity, efficiency of aphids in vectoring, weather conditions during the growth period, genetic tolerance and the growth stage of the crop affected natural infection by PVY- and EPMV-complex. Exploitation of the genetic potential of introduced elite genotypes and their progenies along with breeding elite local cultivars for resistance and excluding aphid vectors at young (seedling) stage of the crop plants could be helpful for minimizing losses in yield and quality of hot pepper due to infections by PVY- and EPMV-complex.     

Sources and inheritance of earliness in tropically adapted indeterminate common bean

Summary Nineteen early maturing, indeterminate common bean parents were crossed with a tester line of normal maturity. All parents, F₁ hybrids, F₂'s, and backcross generations were evaluated at CIAT-Palmira, Colombia. All 19F₁ populations flowered and matured almost as early as the respective early parent (mean of 61 vs 59 days). The F₂ populations were slightly less early (63 days), but were still earlier than the mean of the two parents (65 days). Additive effects for days to maturity were usually larger than dominance or interaction effects. Narrow sense heritability for days to flower and maturity were high (greater than 0.67), while heritabilities of absolute and relative duration of pod filling were low (0.17 to 0.50). Also, our data indicated that for each day of increase in earliness, yield potential will decrease 74 kg/ha.     

Evaluation of yield stability of cowpea under sole and intercrop management in Nigeria

Summary Nine cowpea (Vigna unguiculata (L.) Walp.) breeding lines were grown in 13 experiments under sole crop and intercrop management, with and without insecticide application, in Nigeria. Cowpea was intercropped with cassava (Manihot esculenta Cranz), maize (Zea mays L.) and maize-cassava in the forest zone and with sorghum (Sorghum bicolor Moench.) and millet (Pennisetum glaucum (L.) R.Br.) in the savanna zone. Line by cropping system interactions were significant in 5 of 13 experiments and line by insecticide treatment interactions were significant in 2 of 13 experiments. Cowpea yield was severely depressed in intercropped plots and in plots to which no insecticide was applied. Among-environment variation in cowpea yield was greater when no insecticide was applied. Within each management treatment, the yield performance and stability of the cowpea lines was examined. Stability was assessed both by examining among-environment coefficients of variation and by regression analysis. Several of the breeding lines evaluated appeared promising under different levels of management and in a diversity of environments.     

Effect of plant density on selection for seed yield in two population types of Phaseolus vulgaris L.

Summary Pedigree selection for seed yield, using early generation yield tests, was practiced from the F₂ to F₇ in two populations of common bean (Phaseolus vulgaris L.) in three plant densities: 66, 133, and 266 thousand plants ha^-1 at CIAT-Palmira, Colombia. The six highest yielding lines selected from each plant-density, along with 13 parents, were evaluated in a 7×7 lattice design with three replications at the three densities utilized for selection, and at 399,000 plants ha^-1 in 1988 and 1989.Based on the mean performance of selected lines and the mean of the parents, selection for seed yield was effective in all densities in both populations. However, none of the lines selected from the population within the race Mesoamerica (TC 4673) significantly outyielded their best parent under any plant density. The highest yielding lines selected from the interracial population (TR 4635) outyielded their best parent irrespective of the plant-density used for selection. The highest yielding line originated from the highest density used for selection. Low density was neither good for selection nor for evaluation and identification of high-yielding cultivars of common bean. There was no significant difference between the mean yield of lines selected at the intermediate and high population densities. The effects of plant density, year, and their interactions were significant for seed yield.