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Yield of common bean (Phaseolus vulgaris L.) is highly constrained by water deficit especially when this occurs during the reproductive development. The purpose of the study was to determine the association of the morphophysiological traits with water stress and how this affects grain yield in common beans. A field experiment involving eight common bean genotypes and three water regimes (50 %, 75 %, and 100 % of crop evapotranspiration) was conducted at National Irrigation Research Station, Mazabuka district during the 2012 growing season. A Split plot design with four replications was used; with soil moisture regime (main plot) and the genotypes (subplot). Based on variation in water stress tolerances, 8 test genotypes - Gadra, KE 3, KE 4, ZM 4488, SER 76 SER 180, SER 89 and CAR-ZAR were used. Water stress treatments were imposed at pre-flowering stage and was discontinued after 43 days when the crop was in its late reproductive stage. Significant differences were found among genotypes for Chlorophyll a (Chl a), Chlorophyll b (Chl b), Total Chlorophyll, Relative water content, Grain yield, Number pods per, Seed weight, Seeds per pod and Days to 50 % flowering under the three water stress conditions. The grain yield in normally irrigated condition (2191.3 kg ha-1) was 60 % higher than in high water stress condition (866.2 kg ha-1), while in the low water stress condition (1078.3 kg ha-1), the reduction in grain yield was 50.8 %. There were significant genotype by environment showing that the genotypes behaved differently under the different growing conditions. Results suggested that Gadra, KE 4, ZM 4488, and SER 180 were water stress tolerant while the SER 89, CAR-ZAR, KE 3 and SER 76 were water stress sensitive genotypes. These results suggest that a selection method based on 100 SW, Chl a, Chl b, and NPP can be used in breeding for bean genotypes to water stress.

This study was conducted to determine the relationship between ambient temperature during growing season on tuber β-carotene content and yield of four orange-fleshed sweetpotato varieties; Orange Chingovwa, Olympia, Kokota and Zambezi. A split plot experiment design with the environment (main plot) and variety (subplots). The environments were: High-temperature site (HTS) (average temperature of 38.5°C) and moderate temperature site 1 (MTS 1) and moderate temperature site 2 (MTS 2) (average temperature 32.2 and 31.2°C, respectively). Results suggested that assimilate partitioning between below ground components (tubers) and above ground components (leaves and vines) were inversely related and influenced by ambient temperature during development. Low temperatures favoured tuber formation. The HTS had lower yield (0.97 ton ha-1) compared to the two moderate temperature sites that had tuber yield between 11.96 and 9.41 ton ha-1. The HTS at 7.23 mg/100 g had lower β-carotene contents compared to the MTS sites (≈15.5 mg/100 g). Zambezi and Orange Chingovwa had higher β-carotene content at 21.21 mg/100 g and (18.85 mg/100 g). Kokota had the least β-carotene (3.28 mg/100 g Vine Yield (VY) was significantly different for sites. HTS had the highest VY and leaf area (23.6 t/ha) while the two MTS had low VY of 8.7 and 12.9 t/ha. Key words: Partitioning, tuber, leaf area, vine, yield.

The study evaluated developmental responses associated with plant population density stress applied at different phenological phases and effects on grain yield in determinate and indeterminate soybean (Glycine max L.). A split-split plot design with four replications, with variety (main plot), plant density (sub plot) and thinning time (sub-subplot) was adopted. Two determinate genotypes (Lukanga and SC Semeki) and an indeterminate type (Mwembeshi) were used. Plant density stress was imposed by planting at supra optimal densities (700, 600 and 500 K plants ha-1) (K representing 1000) and stress was removed by thinning to the recommended density (400 K plants ha-1) at different phenological stages. Plant density had little effect on grain yield. Thinning time influenced root to shoot ratio, number of grains per pod, yield and harvest Index (HI). Lukanga had the highest grain yield (2.43 tons ha-1), followed by Mwembeshi (1.95 tons ha-1) and lastly SC Semeki (1.17 tons ha-1). Lukanga exhibited reproductive plasticity, while SC Semeki showed vegetative plasticity. Mwembeshi an indeterminate type suggested non-plastic or ‘elastic’ response. The lack of effect on planting density exemplified by constant yield at different plant densities suggests that maintaining low seed rates is more economical given the high cost of seed. Key words: Partitioning, determinate, indeterminate, reproductive plasticity, vegetative plasticity.

Rose (Rosa spp.) production for cut flowers is an integral part of the horticultural industry. However, because roses are exotic plants they exhibit serious problems related to poor climatic adaptation. A study was conducted at the School of Agricultural Sciences, University of Zambia to evaluate chemicals to extend flower shelf life. The cultivar ‘Akito’ was used as the test variety. Benzyl amino purine ([6- (benzylamino) purine]) (BAP), a growth regulator and aluminium sulphate (an acidifying reagent) were applied to cut flowers at 0, 5, 10, 15, and 20 mg L-l and 0, 400, 800 and 1200 mg L-l, concentration, respectively. BAP was applied to the plants in the greenhouse 2 days before harvest. A randomised complete block design arranged as a two- factor- factorial arrangement with three replications was used. Harvesting was done at the loose open calyx stage. Aluminium sulphate was applied to the holding solution where flowers were kept after harvest. The pH of the holding solution, blossoming (flower opening), leaf color of subtending leaves and bacterial population were monitored. The 400 mg L-l aluminium sulphate treatment caused an increase in acidity. There was concurrent decline in bacterial count in the first three days of application at less than 1 x 106 which was five times lower than the water control treatment. Bacterial population followed the trend of water acidity. The 20 mg L-l BAP application increased shelf life by 35 %. The results showed that BAP and aluminum sulphate treatment could enhance shelf life. Int. J. Agril. Res. Innov. Tech. 10(1): 6-12, June 2020

Maize is an important cereal in sub-Saharan Africa. Its production is however hampered by both biotic and abiotic factors. Among the abiotic factors, heat stress has been reported to cause yield losses. The objective of this study was therefore to identify tolerant genotypes to heat stress and determine the type of gene action conditioning heat tolerance in tropical maize. To achieve these objectives, five maize inbred lines (L2 [P1]; DTS 6,36 [P2]; L5527 [P3]; DTS 6,6 [P4] and DTS 6,92 [P5]) were mated in a 5 x 5 half diallel. Their progeny were evaluated at a heat prone site (Lusitu) and at the University of Zambia (UNZA), a control site. The experiment was laid as a randomised complete block design with two replications in each site. Highly significant differences (P ≤ 0.01) were obtained among genotypes in Lusitu with regards to all measured parameters. The crosses[P2 (DTS 6,36) x P4 (DTS 6,6)] and [P4 (DTS 6,6) x P5 (DTS 6,92)]were identified as tolerant genotypes to heat stress. Further analysis showed that the general combining ability (GCA) effects for parent P4 (DTS 6, 6) and P3 (L5527) were positively and negatively significantly different (P ≤ 0.01) from zero respectively with regards to all measured parameters. On the other hand, crosses [P1 (L2) x P3 (L5527)] & [P4 (DTS 6,6) x P5 (DTS 6,92)]were found to possess desirable significant (P ≤ 0.05) specific combining ability (SCA)effects from zero. The results of baker’s ratio obtained for responseto heat stress for all secondary traits measured were found to be greater than 0.88. This implied that additive gene action was more important in conditioning the response of these traits to heat tolerance.

An experiment was conducted to determine the effects of increasing soil phosphorus under water stress conditions on yield and plant development in bean (Phaseolus vulgaris L.) genotypes with contrasting drought susceptibility tolerances. A split-split plot design with genotypes (main plot), two water regimes (split plot) and three phosphorus rates (split-split plot) was used. Water regimes were imposed by irrigating at 50% ET (water stress) and 100% ET (no stress). Phosphorus (P2O5) was applied at planting at the following rates- 0, 40 and 70 kg P ha-1. The two bean lines used were Gadra (high drought susceptibility) and KE- 3 (low drought susceptibility). Water stress significantly reduced plant height, shoot biomass, pod length, seeds per pod, pods per plant, days to maturity and grain yield in both genotypes. Phosphorus significantly increased grain yields mainly through increased number of pods per plant and 100-seed weight. Higher increases were observed in Gadra where moderate P application increased yield from about 250 to 1,000 kg ha-1 and high P increased yield to 1,600 kg ha-1. The results suggested that high P foraging and utilisation efficiency were inversely related. Key words: Biomass, soil nutrients, phytotoxicity, yield, yield components.

A study was conducted to determine phenotype plasticity responses in soybean genotypes subjected to plant density stress at different phenological stages. Plants planted at supra optimal population density (500,000 plants per hectare) were thinned to 400,000 population density at 4 developmental stages: V1 (Full expansion of first trifoliate leaves), V3 (Four nodes with 3 unfolded trifoliates), V6 (Seven nodes, with 6 unfolded-unifoliate) and R2 (Full bloom with an open flower at the top). The study was conducted in Chilanga, Zambia. Three varieties: Dina, an indeterminate variety and Magoye and Sc Safari determinate varieties were used. A randomized complete block design arranged as a factorial design with two treatments: varieties and thinning stage and four replications were used. Variety had significant effects on days to flowering, biomass, branching, leaf chlorophyll content, plant height, seed weight, and total grain yield. Thinning time influenced number of branches, plant height, above ground biomass and yield. Plant height increased between 32 and 39% for the thinned treatments. Early thinning increased biomass; thinning at the V8 stage increased biomass by 39% compared to the unthinned treatments. Magoye at 2.42 tons/ha had a higher yield, compared to Dina (2.37 tons/ha) and Sc Safari (1.76 tons/ha). Early thinning (T1) reduced yield by 28%. Soybean varieties used in this study exhibited significant vegetative plasticity. Reducing plant density especially in early vegetative phases reduced plant height, increased branching and biomass allocation to vegetative plant parts. Key words: Biomass, determinate, indeterminate, phenology, vegetative plasticity, yield, yield components.

An experiment was conducted to determine the effects of shade on plant development, macronutrient and secondary metabolites in roselle (Hibiscus sabdariffa). Three roselle accessions (ZM 5729, ZM 5738 and ZM ZM5748) acquired from the Zambia National Plant Genetic Resource Centre were used and shade was imposed by intercropping roselle with maize (Zea mays). A Split plot design with shade as main plot and genotype as split- plot was used. Nutritional and development parameters were monitored. At 14 weeks shaded plants had about a three-fold decrease in branches numbers compared to unshaded ones. Plant height was higher in unshaded treatments (120 cm) compared to shaded (83 cm). Plant height of ZM 5738 was significantly higher than the other two accessions. Shading reduced dry matter accumulation by almost 75 % across genotypes with about 20 g per plant in shaded treatments and 73 g in unshaded treatments. Nutrient reductions were highest in fat (60.6 %), fibre (48.4 %), protein (37.8 %), and lowest in ash (27.3 %). In terms of strength of partitioning the pattern was: branches ˃ leaves ˃ roots ˃ squares ˃ flowers. The carbohydrate content increased with shading (10.6 %). Vitamin C content was higher in unshaded treatments in comparison with shaded conditions. ZM 5738 had the highest content followed by ZM 5748 and ZM 5729 had the least content. Oxalates which are an anti- nutrition factor increased with shade. The findings showed that there is significant variation among genotypes and in future selections can be made to choose the most productive genotypes.Int. J. Agril. Res. Innov. & Tech. 8 (1): 7-13, June, 2018

Understanding morpho-physiological factors associated with yield decline at high density in soybean (Glycine max L.) can assist in optimizing productivity and seed quality. The objective of this study was to determine effects of different spacing on development and seed quality. The study tested the concept of yield plasticity. Five varieties that included determinate (SC Safari, Dina and Magoye) and indeterminate (Kaleya and Pan 1867) and three densities (300,000, 400,000 and 550,000 plants/ha) were used. A randomized complete block design arranged in 2 factor- factorial with variety and plant density and 4 replications was used. The experiment was done at Seed Control and Certification Institute in Chilanga, Zambia in 2015. Parameters assessed included: height, branches/plant, chlorophyll, nitrogen, 50 % flowering, pod-fill time, maturity duration, biomass, seed quality, yield and yield components. Significant effects for variety were present for all parameters while plant density effects were highly significant for number of branches/plant, biomass yield, pods/plant, seeds/pod and yield. Interaction effects were observed for pods/plant and seeds/plant. Traits positively and significantly correlated to yield were height, canopy biomass yield, pods/plant and seeds/plant. Biomass, pods/plant, seeds/plant and 100 seed weight contributed significantly to total variation of grain yield. Plant height, biomass yield, number of pods/plant, number of seeds/plant and hundred seed weight were critical parameters determining yield elasticity. Kaleya, Pan 1867 and Dina appeared more tolerant of planting at high density.

The objective of the study was to identify the grafting method, which will have a higher success rate of scion development. The study was conducted at Mount Makulu Central Research station in Chilanga, Zambia (15o33’S / 28o11’E) from April 2010 to November 2011. The study had 4 vegetative propagation methods that varied in the treatment of the rootstock and scion. The four methods were Standard T- budding (STB); Modified TBudding with decapitation (TBD); T- budding with scion bending (TBB); Crown grafting (CG). Bud take, shoot growth, leaf emergence and Leaf area index were measured up to 11 weeks after treatment (WAT). With CG there was 100 % bud take. STB had a bud take of 58.3 %. TBD had a bud take of 50 %. The lowest bud take percentage was recorded in TBB, which had a bud take of 41.7 %. At 5 weeks the STB and TBB treatment had shoot length of 0.7 and 1.0 cm respectively which were the shortest; this was followed by the CG treatment at 15.3 cm and the modified TBD with apical shoot decapitation (21.7 cm). STB shoots did not start growing until about 5 weeks, which was 2 weeks after the rootstock was cut off. At 5 weeks, the TBB and STB were yet to form leaves. The CG had close to 20 leaves and the TBD had almost 15.2 leaves. At the end of 11 weeks, the TBB had the highest number of leaves. Across the grafting methods; the Leaf area exhibited a pattern similar to leaf number; it kept on doubling every 2 weeks to until the 9th week after which the increase was negligible. At 11 weeks, the highest leaf area was in the TBD followed by the STB and lowest in the CG treatment.Int. J. Agril. Res. Innov. & Tech. 7 (1): 64-70, June, 2017

This study evaluated stability, maturity and the efficacy of different poultry litter for possible use in container plant production. Three types of poultry manure- Battery cage (BC), Deep litter (DL) and Free range (FR) were used, with Kraal manure (KM) as a comparison. The experiment was set up as a Split- split design with 6 replications. Composting period was main plot, poultry manure type the split plot and mixing ratio as the split- split plot. The litter was mixed with garden soil in 2 ratios (3:1 and 1:1 soil: manure ratio) and tested for up to 12 weeks. Rape (Brassica napus) was used as a bioassay for maturity, which was determined at 1 month, 2 months and 3 months. The pH declined slightly from 7 to about 6 for all treatments except for the kraal manure. Respiration trends were similar to electrical conductivity. Within 2 weeks of curing the respiration rate for all manures declined to below 4 mg CO2- C/ kg. At the end of 12 weeks curing Battery cage had highest total nitrogen (2.32 %), followed by Free range (1.25 %), Deep litter (0.73 %) and Kraal manure was lowest at 0.35 %). Maturity (rape survival) increased with compositing time. After 3 months of curing Kraal manure had highest survivability of rape. The DL at 1:1 ratio had the lowest survival of 67%. At 12 weeks except for BC at 3:1 all treatments had 100 % survival. The results showed that nitrogen rich manures (DL and BC) needed longer curing in order for them to reach maturity.

The problems associated with heavy metal contamination are widespread and are especially common in developing countries. A pot study was carried out to evaluate the effectiveness of Sunflower (Helianthus annuus), Sorghum (Sorghum bicolor) and Chinese cabbage (Brassica chinensis) at removing lead from the soil. Lead contaminated soils were collected from Kabwe near the old Lead mine and characterized for total and extractable lead, pH, organic matter, texture and cation exchange capacity. The average total and extractable lead concentrations were 23 313 and 5876 mg/kg, respectively, in contaminated soil compared to 57.75 and 10.02 mg/kg in uncontaminated soil. The contaminated soil was then diluted with uncontaminated soil to achieve five contamination levels of 5876, 2500, 1000, 500 and 10.02 mg/kg. Test plants were grown for 10 weeks after which below and above ground dry biomass yields were determined and tested for lead concentration and uptake. Results from this study show that Chinese cabbage is more effective at lead uptake than Sunflower and Sorghum. Results also show that high soil lead concentration results in poor plant growth, low biomass yield and increased lead accumulation in plant tissue.

SummaryTen apple cultivars (Malus domestica Bork) Ein Shemer, Anna, Rome Beauty, Tropical Beauty, Alexander, Orleans, Winter Banana, Black John, Starking Delicious and Red Delicious were evaluated for their suitability for tropical Zambian conditions. Winter Banana, Black John, Starking Delicious and Red Delicious, which were mostly high-chill cultivars, showed poor vegetative development: delayed budbreak, shoot growth and progressive loss of vigour and most of the trees died before maturity. Of the remaining low-chill cultivars, ‘Ein Shemer’ had the highest fruit yield at 49 6 2.3 kg tree21 and ‘Alexander’ the lowest (5.3 6 1.0 kg tree21). This response was due to the high number of fruits per tree, ‘Ein Shemer’ had up to 907 6 83.7 per tree whereas low yielding cultivars like ‘Rome Beauty’ and ‘Tropical Beauty’ had fewer than 106 6 25.3 fruits per tree. The individual fruit weight was inversely related to the total number of fruits per tree. It ranged from 58 6 5.1 g in Ein Shemer to 191 6 24.8 g in ‘R...

The effects of root restriction, induced by root restriction bags, was evaluated on `Yoshida' Ponkan mandarin (Citrus reticulata Blanco). Trees were planted in 0.02-m3 volume root wrap bags (RWBs), which were made from woven polystyrene fiber, or root control bags (RCBs) made from nonwoven UV-stabilized Duon polystyrene fibre with plastic bottoms. A direct soil planted, nonrestricted root treatment (DPC) was included as a control. After 3 years, reductions in height (14% to 29%), canopy volume (66% to 43%), girth (10% to 22%), and leaf area (8% to 12%) were recorded in both of the root restriction treatments. Greater reductions occurred in the RWB treatment. Photosynthesis, transpiration, water potential, and leaf carbohydrate content were not affected by root restriction although soil moisture content was lower in the root restricted treatments. Fruiting efficiency (i.e., number of fruit per unit volume of tree canopy) improved only in the RWB treatment over the control. Total soluble solids and the fruit color index were enhanced by root restriction.

Seasonal changes of sucrose, glucose and fructose were monitored in the bark (phloem) and xylem in Ponkan mandarin (Citrus reticulata Blanco cv. Yoshida). Sucrose was the most abundant sugar. A decline in bark sucrose content coincided with the major fruit abscission period. Stem girdling was carried out at anthesis (May), end of June drop (July), start of autumn (September) and in early winter (November). Girdling in July and September slightly increased leaf sugar content. At peak starch content (in winter), the September girdled treatment had the highest starch content. May girdling increased fruit set significantly and also improved fruit color. July and September girdling improved fruit size, but late girdling (November) had no effect on fruit size. Flowering and fruit set in the following year were closely related to starch content in the previous winter: they were highest in September girdled trees and lowest in May girdled trees.

The effects of water stress and/or chemical growth retardant, paclobutrazol, applied either as foliar spray or soil drench, on photosynthesis, tree vegetative and reproductive growth in young ponkan trees (Citrus reticulata Blanco cv. Yoshida) were evaluated. Paclobutrazol was applied when spring shoots were about 5 mm in length, either as an 840 ppm foliar spray or as a soil drench (0.5 g active ingredient per tree). Soil water stress of up to pF 2.95 was gradually imposed on the trees before re-watering. Water stress improved fruit set, whereas paclobutrazol reduced it. The proportion of abnormal flowers was increased by applying paclobutrazol without water stress. Abnormal flowers were reduced when paclobutrazol was applied in combination with water stress. Tree height increased about 14% for soil drench and 60% for foliar applied paclobutrazol based on initial heights at beginning of the experiment. Water stress caused up to 20% reduction in leaf expansion, reduced photosynthesis, and moderately reduced tree growth. Application of paclobutrazol ameliorated photosynthetic reductions associated with water stress, by maintaining higher photosynthetic and transpiration rates during water stress and ensuring quicker recovery after re-watering.

The annual partitioning dynamics of assimilated photosynthates in a low yielding ponkan (Citrus reticulata Blanco cv. Yoshida) and a high yielding cultivar, satsuma mandarin (Citrus unshiu Marc.) were compared. Starch, soluble sugars and hemicellulose in all above ground tissues were monitored at monthly intervals over a period of one year. Ponkan showed a continuous decrease of sugars and starch in all tissues except for mature wood from anthesis (May) until the end of fruit set period (July). Towards fruit maturity and approach of winter, there was a high accumulation of non-structural carbohydrates in the tissues. Maximum carbohydrate content in most tissues was reached in mid-winter (December to Januuary). A close relationship was found between non-structural carbohydrate accumulation patterns in the new leaves and shoots and fruit growth rate indicating that low sink strength of the developing ponkan fruit and inefficient mobilization of non-structural carbohydrates from the current season' s source leaves and mature wood caused low fruit set and yield in ponkan, in contrast to the satsuma mandarin fruit.