Taking a moment to measure networks—an approach to species conservation

Landscape Ecology - Network-theoretic tools contribute to understanding real-world system dynamics, such as species survival or spread. Network visualization helps illustrate structural...     

Fortified cassava peel compost amendment for Amaranthus: Influence on plant growth,nutrients uptake and on soil nutrient changes

Nutrient supply through organic sources usually requires fortification for timely and optimum release of plant nutrients to achieve optimum crop performance. A pot experiment was conducted in a screen house to determine the optimum rate of cassava peel compost (CPC) fortification that supports optimum Amaranthus (Amaranthus cruentus L.) plant nutrient contents and residual soil nutrient contents. A compost of cassava peel and poultry manure was applied at 2.5; 5.0 and 7.5 t ha^?1each complemented with either 25 or 50 kg nitrogen (N), using nitrogen, phosphorus and potassium (NPK) 20-10-10 at 2 weeks before sowing Amaranthus. An unfertilized treatment served as control. Seeds were sown in plastic containers with a surface diameter of 24 cm filled with 5 kg soil, with a drain underneath. Seedlings were thinned to 4 plants/pot 2 weeks after planting. Plants were harvested at 5 weeks by ratooning and plant re-growth also harvested after 5 weeks. Soil pH was lower with high rates of 5.0 and 7.5 t ha^?1 CPC while the organic matter content was increased with increased CPC rate. Soil N was reduced but reflected in increased plant shoot and root N, with compost application. Soil P was generally increased but was not reflected in plant contents. Soil K contents were reduced and were reflected in increased plant contents. Application of 2.5 t ha^?1 CPC, fortified with either 25 or 50 kg N ha^?1 gave the optimum Amaranthus shoot nutrient contents with optimum residual soil nutrient contents.     

“Egusi” melon seed yield,proximate content and soil nutrient changes with poultry manure fertilization

Abstract

“Egusi” melon (Colocynthis citrullus L.) is a seed vegetable whose yield is limited by nutrient supply. Two field experiments were conducted with “Egusi” melon at the Crops Research Farm of the Federal University of Agriculture, Abeokuta, Nigeria, to evaluate response of poultry manure (PM) rate on seed yield, seed proximate content, and changes in soil nutrients. The study was conducted from May to August 2013 and repeated same period in 2014 using PM at: 0, 2, 4, 6, 8, and 10 t ha^?1. With the first planting, seed yields of 458 and 452?kg?ha^?1 from applications of 6 and 8 t ha^?1 PM were similar with the highest of 522?kg?ha^?1 from application of 10 t ha^?1 PM. The second planting, with residual fertilizer effect had a higher seed yield of 242?kg?ha^?1 from application of 10 t ha^?1 PM. Number of seeds per fruit was higher; 183 seeds per fruit in the first planting and 163 seeds per fruit in the second planting, from plants treated with 10 t ha^?1 PM. Shelling percent was comparable in both experiments. It was 19.5% with application of 10 t ha^?1 PM and 33.4% with the unfertilized plants for the first planting but was 28.0% with application of 10 t ha^?1 PM and 31.3% with the unfertilized plants for the second planting. Seed crude protein, crude fiber and ash contents were enhanced with application of 10 t ha^?1 PM. Soil pH in the first planting was reduced from initial 6.8 to 6.6 with the unfertilized plants and to 6.7 with applications of 2 and 10 t ha^?1 PM, but increased to 7.1 with application of 6 t ha^?1 PM. In the second planting, it was reduced to 5.0 with applications of 0, 2 and 4 t ha^?1 PM but to 5.3, 5.1, and 5.2 with applications of 6, 8, and 10 t ha^?1 PM, respectively. The initial total N of 0.14% was reduced to 0.12% with applications of 6 and 8 t ha^?1 PM but to 0.11% with the other treatments in the first planting; but reduced to 0.08% with applications of 2 and 4 t ha^?1 PM and to 0.06 and 0.09% with applications of 8 and 10 t ha^?1 PM, respectively, in the second planting. Available P in the first planting was reduced from an initial 17.62?mg kg^?1 to 4.32?mg kg^?1with the control treatment and to 6.74 and 5.83?mg kg^?1 with applications of 2 and 4 t ha^?1 PM, respectively, but to 8.32 and 8.24 with applications of 8 and 10 t ha^?1 PM, respectively. In the second planting, it was reduced to 1.92?mg kg^?1with the control treatment and to 2.53 and 1.81?mg kg^?1 with applications of 2 and 4 t ha^?1 PM, respectively but to 1.90 and 1.56 with applications of 8 and 10 t ha^?1 PM, respectively. Application of 10 t ha^?1 PM supplying 19?kg N, 0.5?kg P and 27?kg K per ha was adequate for enhanced seed yield and proximate contents of “Egusi” melon.     

Landscape connectivity and predator–prey population dynamics

Landscapes are increasingly fragmented, and conservation programs have started to look at network approaches for maintaining populations at a larger scale. We present an agent-based model of predator–prey dynamics where the agents (i.e. the individuals of either the predator or prey population) are able to move between different patches in a landscaped network. We then analyze population level and coexistence probability given node-centrality measures that characterize specific patches. We show that both predator and prey species benefit from living in globally well-connected patches (i.e. with high closeness centrality). However, the maximum number of prey species is reached, on average, at lower closeness centrality levels than for predator species. Hence, prey species benefit from constraints imposed on species movement in fragmented landscapes since they can reproduce with a lesser risk of predation, and their need for using anti-predatory strategies decreases.     

Soil temperature and moisture content changes with growth and yield of cassava/vegetable intercrops

Field experiments were conducted at the Federal University of Agriculture Abeokuta, Nigeria to evaluate the changes in crop microenvironment, growth and yield performance of intercropping okra, pepper and pumpkin with cassava. The vegetables were planted sole and in mixtures with three cassava cultivars: Idileru, Odongbo and TMS30572. Intercropping reduced weed dry weight and soil temperature but increased soil moisture content, light interception and number of earthworm casts. Cassava/pumpkin intercrop increased soil moisture content, light interception and number of earthworm casts but reduced soil temperatures and weed dry weight compared with cassava/okra and cassava/pepper intercrops. Vegetative characters and fruit yields of okra, pepper and pumpkin were not affected by intercropping. Leaf area index (LAI) of intercropped cassava with pumpkin was reduced but not with okra and pepper. Land equivalent ratio was higher in cassava/okra and cassava/pepper than in cassava/pumpkin intercrop. Cassava/vegetable intercrop is a viable cropping option for high productivity and provision of suitable microenvironment for growth. A short, early-maturing cassava cultivar with a moderate LAI is better adapted in mixture with vegetables.