Total Plant Dry Biomass Research Articles

Multiple taxa inoculants of arbuscular mycorrhizal fungi enhanced colonization frequency, biomass production, and water use efficiency of cassava (Manihot esculenta).

Increasing water use efficiency (WUE) in crops is critical to maintaining agricultural production under climate change-exacerbated drought. One of these approaches may consist of leveraging on the beneficial interactions between crops and arbuscular mycorrhizal fungi (AMF). In this study, we investigated how inoculation with AMF from three different taxa (Claroideoglomus etunicatum (T1), Gigaspora margarita (T2), and Rhizophagus irregularis (T3)) and their combination (T123) and a non-inoculated "control" treatment in a greenhouse could achieve increased biomass production and water use efficiency in cassava under three levels of water availability (100% PC, 60%-moderate stress, and 30%-severe stress). Whereas T1 and T2 resulted in a lower growth rate for the plants than the control, T123 enhanced cassava height and the number of petioles and leaves. T123 and T3 increased the total plant dry biomass in comparison with uninoculated plants by 30% and 26%, respectively. The T123 and plants inoculated with T3 significantly increased cassava above-ground biomass by 19% as compared to T1 (8.68 ± 2.44g) and T2 (8.68 ± 2.44g) inoculated plants. T123 resulted in higher WUE, which was validated by the leaf carbon (δ13C) isotopic signature, significantly outperforming cassava with T1 and T2, yet there was no difference between the control and T3. Overall, this study demonstrated that the use of multiple AMF from different taxa can increase cassava growth and WUE under greenhouse conditions.

Unraveling the role of multi-walled carbon nanotubes in a corn-soil system: Plant growth, oxidative stress and heavy metal(loid)s behavior

In the age of nanotechnological advancement, carbon nanotubes (CNTs) are drawing global attention. However, few studies have been published on the crop growth responses to CNTs in heavy metal(loid)s contaminated environments. A pot experiment was conducted to assess the effect of multi-walled carbon nanotubes (MWCNTs) on plant development, oxidative stress, and heavy metal(loid)s behavior in a corn-soil system. Corn (Zea mays L.) seedlings were cultivated in soil containing Cadmium (Cd) and Arsenic (As) that had been primed with 0, 100, 500, and 1000 mg kg−1 MWCNTs. The application of 100 and 500 mg kg−1 MWCNTs improved shoot length by 6.45% and 9.21% after 45 days, respectively. Total plant dry biomass increased by 14.71% when treated with 500 mg kg−1 MWCNTs but decreased by 9.26% when exposed to 1000 mg kg−1 MWCNTs. MWCNTs treatment did not affect Cd accumulation in plants. On the other hand, the bio-concentration factor of As was inversely associated with plant growth (p < 0.05), which was declined in MWCNTs treatments. Oxidative stress was aggravated when plants were exposed to MWCNTs, thus activating the antioxidant enzymes system in the corn. In contrast, TCLP-extractable Cd and As in soil significantly decreased than in the control. Additionally, the soil nutrients were changed under MWCNTs treatments. Our findings also revealed that a particular concentration of MWCNTs can mitigate the toxicity of Cd and As in corn seedlings. Therefore, these results suggest the prospective application of CNTs in agricultural production, ensuring environmental and soil sustainability.

PENGARUH KOMPOS SERBUK SABUT KELAPA TERHADAP PERTUMBUHAN DAN HASIL TANAMAN CABAI RAWIT PADA TANAH PODSOLIK MERAH KUNING

This study aims to determine the effect of composted coconut coir dust on growth and yield of cayenne pepper on red yellow podzolic soil. This research was conducted in the experimental farm of the Faculty of Agriculture, University of Tanjungpura Pontianak, started from February to July 2014. This study used a field experiment with completely randomized design consisting of single factor i.e composted coconut coir dust, with six level treatments: S1 (800 g/polybag); S2 (900 g/polybag); S3 (1000 g/polybag); S4 (1100 g/polybag); S5 (1200 g/polybag); dan S6 (1300 g/polybag), consists of 4 replications, with 3 plant samples each. The variables observed in this study include, plant height (cm), number of fruit per plant (fruits), the fruit biomass per plant (g), total dry biomass (g), and root volume (ml). The results showed that the application of composted coconut coir dust here not a significanlly affected plant height, number of fruit per plant, the fruit biomass, total plant dry biomass, and root volume.Keywords: Cayenne Pepper, Composted, PMK

Arbuscular mycorrhizal inoculation increases drought tolerance and survival of Cenostigma microphyllum seedlings in a seasonally dry tropical forest

Seasonally dry tropical forests are characterized by several months of drought. Cenostigma microphyllum is a native woody species widely found in a seasonally dry tropical forest. These forests are in need of restoration and C. microphyllum is a species that can be used to this end. We studied, 1) acute water deficiency using plant in pot, and 2) chronic water deficiency in field conditions in areas with different rainfall gradients, always with two group of plants: inoculated and non-inoculated with arbuscular mycorrhizal fungus. Acute water deficit levels in previously inoculated and non-inoculated treatments were similar, however, after rehydration, the inoculated potted plants showed faster recovery of water status and gas exchange. In field conditions, on the 120th day, before the beginning of the dry period, 100% of transplanted seedlings survived, while the total plant dry biomass did not differ between the inoculated and control groups. The same patterns emerged across rainfall gradient. After 365 days of seedling transplantation, the field survival dropped from 100% to 58%. Sixty-eight percent of the inoculated plants survived, whereas more than half of the non-inoculated individuals did not resprout at the beginning of the rainy season. Among the remaining plants, 63% were from the rainiest plots. The average of CO2 assimilation for both treatments was 2.63 and 9.43 μmol m−2 s−1 in the two driest and wettest plots, respectively. Our results suggest that artificial inoculation appears to be associated with better plant recovery or resilience following low water availability, particularly chronic/prolonged drought. Thus, the present work recommends the use of the seedling production technique, with long roots as well as the previous inoculation with selected native mycorrhizal fungi.

Determination of Appropriate Compost Based Nursery Media Preparation for Pineapple (&amp;lt;i&amp;gt;Annanas comosus MERR L.&amp;lt;/i&amp;gt;) Seedling Growth at South Ethiopia

The experiment was conducted at Awada Agricultural Research Center found at south Ethiopia to determine a proper ratio of compost to top soil ratio that enhanced growth of pineapple at seedling stage. The experiment was arranged in randomized complete block design (RCBD) with three replication. Seedlings were raised from ground slip and planted in plastic pots with width to height (16x22cm) containing compost to topsoil in 0:1, 1:1, 1:2, 1:3, 1:4 and 1:0 ratios as treatments. Seedlings were watered as required and grown for 6 months. determination of pineapple seedling height, leaf length, leaf width, leaf area, leaf fresh weight, leaf dry weight, root number, root dry weight and total plant dry biomass. Data were analyzed using SAS software and means were separated using LSD at 5% probability. The results revealed significant variation among the treatments. All the recorded growth parameters showed progressive increase with increase in the proportion of compost. The compost based nursery media preparation from compost (1:0) and or compost to top soil in one to one (1:1) ratio mixture is performed the best growth of pineapple seedling in terms of plant height, leaf length, leaf width, leaf area, leaf fresh weight, leaf dry weight, root number, root dry weight and total plant dry biomass. Therefore, it is recommendable that compost and or compost to top soil in one to one (1:1) ratio mixture media could be used to grow the best performed pineapple seedling in south ecological zone at nursery level via promoting production and utilization of compost from cheaper locally available materials before transplanting to its production field.

Dry Matter Production Response of Non-conventional Pineapple (&amp;lt;i&amp;gt;Ananas comosus &amp;lt;/i&amp;gt;L.) Seedling to Nursery Media Preparation

Establishment and management of pineapple production mainly lie on the production and supply of quality planting material with desirable root and shoot growth characteristics. Farmers in the South Ethiopia, uses different parts of pineapple like ground sucker, slips, and also crown sucker to transplant to the permanent fields. The fertilization practices were also not common, some farmers use to apply organic fertilizers like animal dung at the permanent field while there is no any media information generated to seedling production. Therefore, this study was conducted to examine the dry matter Production responses of non-conventional pineapple Seedling to organic based nursery media Preparation. The experiment was arranged in RCBD with three replication and six treatments. Six treatment combinations of compost to topsoil ratio in (0:1), (1:1), (1:2), (1:3) (1:4) and compost only (1:0). All the relevant parameters were collected and computed using SAS software. Treatment means were separated using LSD at 5% probability. The results revealed significant variation among the treatments that indicated, the soil based nursery media of compost (1:0) and (1:1) ratio of compost to topsoil responded the best dry matter production response of pineapple seedling in terms of, leaf fresh weight, leaf dry weight, root dry weight and total plant dry biomass. This result suggested that compost (1:0) and or compost to topsoil in (1:1) ratios was useful media to produce the best growth of pineapple seedling before transplanting to its production field.

Integrating Cover Crops as a Source of Carbon for Anaerobic Soil Disinfestation

The adoption of anaerobic soil disinfestation (ASD), a biologically-based method for the management of soilborne pests and pathogens at the commercial scale strictly depends on the availability of effective and low-cost sources of carbon (C). A three-phase pot study was conducted to evaluate the performance of twelve cover crop species as alternative sources of C in comparison to molasses. Buckwheat produced the greatest above-ground and total plant dry biomass and accumulated the largest amount of total C. In the second phase, simulating the application of ASD in a pot-in-pot system, molasses-amended soil achieved substantially higher levels of anaerobicity, and lowered soil pH at 3 and 7 days after treatment application compared to soil amended with the cover crops tested. In the third phase of the study, after the ASD simulation, lettuce was planted to assess the impact of cover crops and molasses-based ASD on lettuce yield and quality. The treatments had limited effects on lettuce plant growth and quality as none of the treatments caused plant stunting or phytotoxicity. Tested cover crop species and molasses had a significant impact on the availability of macro and micro-elements in the soil, which in turn influenced the uptake of minerals in lettuce. Fast growing cover crops like buckwheat or oat, capable of accumulating high levels of C in a relatively short time, may represent a viable alternative to substitute or be combined with standard C sources like molasses, which could provide an on-farm C source and reduce cost of application. Further research is needed to assess the performance of cover crops at the field scale and verify their decomposability and efficacy in managing soil-borne pests and pathogens.

Phenology and growth of lulo (Solanum quitoense Lam) plants grafted onto Solanum hirtum Vahl.

Lulo (Solanum quitoense) is a promising Andean fruit tree that is highly valued in international markets because of its nutritional characteristics, flavor, aroma, and high content of vitamins A and C with antioxidant properties. However, certain sanitary problems, such as Fusarium oxysporum and soil nematodes, pose challenges to the competitiveness of lulo crops. Cultivating lulo plants grafted onto resistant patterns, such as S. hirtum, is a plausible solution to these sanitary issues; so, determining the behavior of grafted plants is relevant. In this study, the phenology and growth dynamics of grafted lulo plants were evaluated with functional analyses based on thermal time (degree days-DD). Completion of the vegetative phase of the lulo required 561 DD from planting to the onset of flower bud sprouting, 715 DD to reach anthesis, 801 DD for fruit set, and a cumulative total of 2,464 DD to reach fruit ripening. The functional analyses showed that Richards’s model fit the dynamics of the growth variables (height, leaf area index, crop growth index, total dry weight, leaf dry weight, and stem dry weight). Of the total plant dry biomass, 39.7% corresponded to the stems, 33.8% was from the fruits, 15.54% was from the leaves, 10.56% was from the roots, and 0.4% was from the flowers. The yield was not affected by the grafting process of lulo S. quitoense onto S. hirtum stocks; on the contrary, the crop population and productivity were maintained for a longer time.

Ethylene response of salt stressed rice seedlings following Ethephon and 1-methylcyclopropene seed priming

Salinity stress is one of the most devastating abiotic stresses affecting rice growth and productivity. Several phytohormones in rice contribute towards salinity response, including ethylene (ET). Furthermore, priming of rice seedlings with different chemicals has revealed new insights in rice stress physiology. Therefore, the hydroponic culture experiment under completely randomized design (CRD) factorial was conducted to study the effects of seed priming with two contrasting chemicals 1-Methylcyclopropene (1-MCP) and Ethephon with respect to ET production under salinity stress levels 0 (control, CK) and 25 mM NaCl (salinity stress, SS) on cultivar Zhongzheyou 1 (indica) with five replications. Results revealed that the use of 1-MCP and Ethephon improved overall rice seedling germination and growth as compared to the unprimed one under salinity stress. Early germination rate was found to be higher in the Ethephon primed seedlings. However, the late germination rate, overall seedling vigor index (SVI), total plant dry biomass (higher as 37.8 and 42% in 1-MCP-primed seeds, and 28.1 and 21.3% higher in Ethephon-primed seeds than no primed seeds under both salinity levels), other agronomic traits, and SPAD value were found to be higher in the 1-MCP primed seedlings. Further, the production of reactive oxygen species was comparatively higher in the Ethephon primed seedlings than the 1-MCP-primed seedlings. In addition, evaluation of ET levels and expression profiling (qRT-PCR) of some ET signaling genes revealed that Ethephon priming resulted in elevated ET concentration and upregulated ET signaling genes, including OsACS1 and OsEIN2. Overall, our results provide a basic idea of the role of rice seed priming with Ethephon and 1-MCP under salinity condition and their effects on the ET interplay. Ethylene response of salt stressed rice seedlings following Ethephon and 1-methylcyclopropene seed priming. SG speed of germination, GE germination energy percentage, 3rd and 6th DAS 3rd and 6th day after sowing, FG final germination.

Exogenous silicon and salicylic acid applications improve tolerance to boron toxicity in field pea cultivars by intensifying antioxidant defence systems.

Field peas (Pisum sativum L.) are widely cultivated throughout the world as a cool season grain and forage crop. Boron (B) toxicity is caused by high B concentration in the soil or irrigation water, and is particularly problematic in medium or heavier textured soil types with moderate alkalinity and low annual rainfall. Previous studies have indicated that B-toxicity increases oxidative stress in plants, and B-tolerance has been considered an important target in field pea plant breeding programmes. Inducers of tolerance may be a promising alternative for plant breeding. Little research has been conducted on the combined use of silicon (Si) and salicylic acid (SA) to remediate B-toxicity in field peas. The present study revealed the physiological and biochemical plant responses of applying Si+SA under B-toxicity (15mgB L-1) on two Brazilian field pea cultivars (Iapar 83 and BRS Forrageira). A semi-hydroponic experiment was conducted using a completely randomized factorial design (2×5): with two field pea cultivars and five treatments which were formed by individual and combined applications of Si and SA under B-toxicity plus a control (control, B, B+Si, B+SA, and B+Si+SA). Si (2mmolL-1) was applied to plants in two forms (root and leaf), while for SA (36 μmol L-1) only foliar applications were applied. Our results demonstrated that the combined use of exogenous Si+SA in field peas increased tolerance to B-toxicity through an intensified antioxidant plant defence system, resulting in a better regulation of reactive oxygen species (ROS) production and degradation. It significantly increased total chlorophyll and carotenoids contents, the activities of major antioxidant enzymes, and reduced MDA and H2O2 contents, resulting in increased fresh shoot and total plant dry biomass. The application of Si+SA alleviated the inhibitory effects of boron toxicity in field peas, resulting in greater plant growth by preventing oxidative membrane damage through an increased tolerance to B-excess within the plant tissue. Therefore, the use of Si+SA is an important and sustainable strategy to alleviate B-toxicity in field pea cultivation.

Effects of varying N, P and K concentrations on growth, biomass, yield and nutritional quality of zucchini squash grown under open and polyhousesoilless culture

Soilless production of vegetables is rapidly gaining momentum and popularity especially in the periurban agricultural space. But this requires suitable technological backstopping in terms of substrate, nutrientmanagement and irrigation scheduling. Open and polyhouse experiments were conducted to study the effect ofvarying levels of N, P and K on the growth, biomass, yield and nutritional quality of zucchini hybrid ‘Champion’under soilless culture. The study was carried out with four different NPK levels and seven replications in acompletely randomized design. The results revealed that the nutrient scheduling of 168 ppm N-NO3, 16 ppm Pand 189 ppm K recorded maximum fruit length (24.12cm), fruit girth (44.4mm), fruit weight (335.6g) and yieldper plant (5.71 kg) and per hectare (71.39 tonnes) under open-field soilless culture. However, maximum plantheight (61.25cm), number of leaves (43.33) and total plant dry biomass (146.8g/plant) of zucchini were recordedwith application of 185 ppm N-NO3, 19 ppm P and 224 ppm K. Between open and polyhouse soilless cultivationof zucchini, highest plant height (80.6cm), number of leaves (47.4), number of fruits (22.3) and total plant drybiomass (184.7g/plant) were recorded with polyhouse conditions. Nevertheless, the highest stem diameter(35.2mm), maximum fruit length (23.2cm), maximum fruit girth (42.9mm), fruit weight (315.4g) and yield per plant(5.27kg) and per hectare (65.8t/ha) were recorded with open-field soilless culture. Zucchini plants raised on Arka Fermented Cocopeat registered higher plant height (54.7cm), stem diameter (35.2mm), number of leaves (39.3),total plant dry biomass (139.8g/plant), number of fruits (16.8), fruit length (23.2cm), fruit girth (42.9mm), fruitweight (315.4g) and yield (5.27kg/plant and 65.8t/ha) compared to soil (3.70 kg/plant and 46.3t/ha). The resultsestablished that the growers can increase zucchini yield and fruit quality and advance fruit production (10 days)by changing from soil to soilless culture.

Potential of Trichoderma spp. as Biological Control Agents Against Bakanae Pathogen (Fusarium fujikuroi) in Rice

Bakanae disease is a major rice disease caused by Fusarium fujikuroi. Infected plants show slender and hyper elongated internodes due to the over-production of gibberellic acid. Application of Trichoderma spp. as biocontrol agent is gaining attention due to high capability in hyperparasitize the soil borne pathogen. The studies aimed to screen and evaluate the bio-efficacy of Trichoderma spp. with antagonistic activities against F. fujikuroi and plant growth-promoting properties. All the 65 Trichoderma isolates were isolated from healthy rice rhizosphere soil. Thirty eight out of 65 Trichoderma isolates exhibited more than 45 Percentage of Inhibition Radial Growth (PIRG) against F. fujikuroi in dual culture plate testing. All selected Trichoderma isolates were further in vitro screened for antagonistic testing: volatile compounds production and hydrogen cyanide production and plant growth-promotion properties: IAA production and phosphate solubilization. Twelve Trichoderma isolates were selected for further evaluation on antagonistic activity against F. fujikuroi, germination rate, plumule and radical lengths and vigor index. Finally, seven of the most potential Trichoderma isolates were selected for greenhouse evaluation. The bakanae disease incidence and disease severity in rice plant treated with respective selected Trichoderma isolates were significant reduced as compared with untreated plant. However, there was no significant increase in plant height between Trichoderma inoculated and uninoculated plants. Moreover, rice plant treated with Trichoderma T61 showed significantly increase in total plant dry biomass as compared to untreated plants. The selected Trichoderma isolates have potential to be developed as biological control agent against F. fujikuroi and also as an alternative for bakanae management.

Effects of biochars produced from different feedstocks on soil properties and sunflower growth

AbstractThe use of biochar as a soil amendment is gaining interest to mitigate climate change and improve soil fertility and crop productivity. However, studies to date show a great variability in the results depending on raw materials and pyrolysis conditions, soil characteristics, and plant species. In this study, we evaluated the effects of biochars produced from five agricultural and forestry wastes on the properties of an organic‐C‐poor, slightly acidic, and loamy sand soil and on sunflower (Helianthus annuus L.) growth.The addition of biochar, especially at high application rates, decreased soil bulk density and increased soil field capacity, which should impact positively on plant growth and water economy. Furthermore, biochar addition to soil increased dissolved organic C (wheat‐straw and olive‐tree‐pruning biochars), available P (wheat‐straw biochar), and seed germination, and decreased soil nitrate concentration in all cases. The effects of biochar addition on plant dry biomass were greatly dependent upon the biochar‐application rate and biochar type, mainly associated to its nutrient content due to the low fertility of the soil used. As a result, the addition of ash‐rich biochars (produced from wheat straw and olive‐tree pruning) increased total plant dry biomass. On the other hand, the addition of biochar increased the leaf biomass allocation and decreased the stem biomass allocation. Therefore, biochar can improve soil properties and increase crop production with a consequent benefit to agriculture. However, the use of biochar as an amendment to agricultural soils should take into account its high heterogeneity, particularly in terms of nutrient availability.

Evaluation of Copper Bioaccumulation and Translocation in Jatropha curcas Grown in a Contaminated Soil

Contamination of soils with copper (Cu) has become a serious problem in the environment. Phytoremediation is an emerging green technology that uses green plants to remediate heavy metal contaminated areas. This study was conducted to evaluate the potential of Jatropha curcas for remediation of soils contaminated with Cu. Seedlings were planted in soils spiked with Cu in amount of 0, 50, 100, 200, 300, and 400 mg kg–1 (Cu0, Cu50,Cu100,Cu200,Cu300, and Cu400) for a period of five months. The maximum height and number of leaves were recorded in control (Cu0) whereas the highest basal stem diameter was found in seedlings exposed to Cu50. Copper concentrations among plant parts were in the following trend: roots > stems > leaves. The highest total Cu concentration (665 ± 1 mg kg−1) and total Cu removal (1.2 ± 0.2%) based on total plant dry biomass were found in Cu400 and Cu50 treatments, respectively. J. curcas exhibited high root concentration factor (RCF > 1) and low translocation factor (TF < 1). Although Cu accumulation by the plant didn't reach the criteria of Cu hyperaccumulators, this species showed a potential to be used in phytostabilization of mildly Cu contaminated areas. However, the plant cannot be used for phytoextraction of Cu-contaminated soils.

Meta-analysis reveals profound responses of plant traits to glacial CO2 levels.

A general understanding of the links between atmospheric CO2 concentration and the functioning of the terrestrial biosphere requires not only an understanding of plant trait responses to the ongoing transition to higher CO2 but also the legacy effects of past low CO2. An interesting question is whether the transition from current to higher CO2 can be thought of as a continuation of the past trajectory of low to current CO2 levels. Determining this trajectory requires quantifying the effect sizes of plant response to low CO2. We performed a meta-analysis of low CO2 growth experiments on 34 studies with 54 species. We quantified how plant traits vary at reduced CO2 levels and whether C3 versus C4 and woody versus herbaceous plant species respond differently. At low CO2, plant functioning changed drastically: on average across all species, a 50% reduction in current atmospheric CO2 reduced net photosynthesis by 38%; increased stomatal conductance by 60% and decreased intrinsic water use efficiency by 48%. Total plant dry biomass decreased by 47%, while specific leaf area increased by 17%. Plant types responded similarly: the only significant differences being no increase in SLA for C4 species and a 16% smaller decrease in biomass for woody C3 species at glacial CO2. Quantitative comparison of low CO2 effect sizes to those from high CO2 studies showed that the magnitude of response of stomatal conductance, water use efficiency and SLA to increased CO2 can be thought of as continued shifts along the same line. However, net photosynthesis and dry weight responses to low CO2 were greater in magnitude than to high CO2. Understanding the causes for this discrepancy can lead to a general understanding of the links between atmospheric CO2 and plant responses with relevance for both the past and the future.

Evaluation of 15 Varieties of Okra (Abelmoschus esculentus(L.) Moench to Field Infestation by Flea Beetles (Podagricaspp.)

The study evaluated 15 okra varieties to field infestation by flea beetles, Podagrica spp., in the early and late planting seasons of 2009, at the Teaching and Research Farm, Federal University of Agriculture, Abeokuta, Nigeria (7°15′N 3°25′E), located in a sub-humid zone. The experiment was arranged in a split plot design, with three replicates. The main plot consisted of spraying regime (sprayed and unsprayed) while the sub-plot consisted of 15 okra varieties: V-35, V2-Oyo, V45-2, NH99/28, NH99/DA NH88/1-8-16-2, Enugu1, Osadep:purple Tall, LD88/1-8-5-2, LD88/1-8-16-2, Ola99/13, Ola3 Local, Olak2005, Short Mouth and Dajofolowo1. Lambda-cyhalothrin was sprayed to the appropriate plots weekly. The results showed that in both early and late seasons, sprayed okra had significantly (P < 0.05) lower number of flea beetles, lower leaf damage per plant, lower number of holes per leaf, wider stem girth, higher total plant dry biomass, higher number of pods compared with unsprayed okra. The sprayed okra had significantly (P < 0.05) higher shoot dry biomass, higher root dry weight, higher total plant dry biomass, wider pods and higher pod weight in the early planting season compared with the late season. Varieties with leaf pubescence, namely NH99/DA, V-35 and Dajofolowo1, had the lowest flea beetle population, leaf damage per plant and number of holes per leaf compared to glaborous varieties. Likewise, the okra varieties NH99/28, V-35 and Dajofolowo1 which have thorny pods had no pod damage at all in both early and late planting seasons. LD88/1-8-5-2 had the highest number of pods per plant, whereas okra variety Ola99/13 had significantly (P < 0.05) higher pod weight during early planting. There was no significant difference in okra pods weight in all varieties evaluated in the late planting season.

Irrigation Frequency Alters Nutrient Uptake in Container-grown Rhododendron Plants Grown with Different Rates of Nitrogen

The influence of irrigation frequency (same amount of water per day given at different times) on nutrient uptake of container-grown evergreen Rhododendron ‘P.J.M. Compact’ (PJM) and ‘English Roseum’ (ER) and deciduous Rhododendron ‘Gibraltar’ (AZ) grown with different rates of nitrogen (N) fertilizer was evaluated. Increased N application rate increased nutrient uptake and plant dry biomass. Irrigation frequency did not significantly influence total plant dry biomass; however, more frequent irrigation decreased net uptake of several nutrients including phosphorus (P), boron (B), and manganese (Mn) uptake in all cultivars; potassium (K), copper (Cu), and zinc (Zn) uptake in AZ and ER; sulfur (S) uptake in ER and PJM; and iron (Fe) uptake in AZ. Additionally, more frequent irrigation of evergreen cultivars increased calcium (Ca) uptake. Covariate analyses were used to compare nutrient uptake among cultivars and irrigation treatments after accounting for the variability in nutrient uptake attributable to differences in biomass and N uptake. For most nutrients, the influence of irrigation frequency on uptake was partially attributable to differences in biomass and N uptake. After accounting for the variability in nutrient uptake associated with biomass or N uptake, increased irrigation frequency decreased P, S, B, Cu, and Mn uptake only in ER and increased Ca uptake in the two evergreen cultivars. Differences in nutrient uptake among cultivars in response to irrigation treatments were related to water and N availability during production and their combined influence on water stress, nutrient uptake, and biomass partitioning. Estimates of nutrient demand and uptake efficiency using nutrient concentrations and ratios are discussed in relation to nutrient management differences for different cultivars and irrigation treatments.

Comparison of estimates of daily solar radiation from air temperature range for application in crop simulations

Daily solar radiation is an input required by most crop growth, development and yield simulation models. It is, however, not observed at many locations, preventing the application of such models. The objective of this work was to (i) evaluate several existing models estimating solar radiation based on daily minimum and maximum air temperature and/or precipitation for seven sites in the world, and (ii) investigate the impact of the estimated solar radiation on grass reference evapotranspiration (ETo) and total plant dry biomass simulations for maize. Comparisons of the solar radiation models was made based on a single modular indicator, I rad, computed using a fuzzy expert system that aggregated several statistical indices, and distribution of mean daily errors over a year. The model estimations were also evaluated according to their ability to simulate ETo and total dry biomass that matches simulations from the observed solar radiation. According to the I rad indicator, there was no solar radiation model which consistently outperformed all the other models at all the sites tested, but I rad indicated models that relatively underperformed at all the sites. The graphical presentation of the mean fluctuation of errors over a year gave a good assessment of the solar radiation estimation models in investigating the temporal behaviour and magnitude of the residuals. Performance of the models according to I rad and simulations of grass ETo and total dry biomass agreed better for models that relatively underperformed. Ranking of the models according to the root mean square error (RMSE) in solar radiation estimation and the RMSE in the grass ETo simulations agreed very well. Comparison of the ranking of the models using the I rad (or the individual statistical indices thereof) and total biomass simulation was difficult because of the difference in the time scale used in calculation of the statistical indices. The difference in simulations of total dry biomass accumulated over the years, however, qualitatively agreed with the graphs of the mean fluctuation of errors over a year. In general, the I rad indicator demonstrated which solar radiation estimation models should be used for crop simulation modelling.

Variable carbon-sink strength of different Glomus mosseae strains colonizing barley roots

Root carbon (C) partitioning was investigated in barley (Hordeum vulgare L.) colonized by one of three strains of the arbuscular mycorrhizal fungus (AMF) Glomus mosseae (Nicolson &amp; Gerdemann) Gerd. &amp; Trappe. The roots of each plant were evenly divided between two compartments of a split-root system and one side was inoculated with one of the three AMF strains. Twenty-three days after inoculation barley shoots were labeled with 14CO2. Twenty-four hours later, plants were harvested and the mycorrhizal (M) and nonmycorrhizal (NM) roots were analyzed separately for 14C. Partitioning of C between M and NM sides differed between the fungal strains: BEG 54 was a strong C sink, BEG 55 was a moderately strong C sink, and BEG 12 showed similar C-sink strength as the non-inoculated control plants. The observed differences in C-sink strength mirrored differences in plant dry biomass. Total plant dry biomass of plants inoculated with BEG 12, BEG54, and BEG 55 represented 81.3%, 65.3%, and 73.4% of the biomass of the control plants, respectively. This paper is the first report of an AMF strain-specific variation of C partitioning in M plants in a split-root system.Key words: arbuscular mycorrhizal fungi, barley (Hordeum vulgare), carbon sink, Glomus mosseae, strain variability.

Influence of plant population and sett size on biomass accumulation and quality of white yam (Dioscorea rotundata) intercropped in coconut (Cocos nucifera) gardens

A field experiment was conducted during 1998 99 and 1999 2000 (May February) at College of Agriculture, Vellayani, Thiruvananthapuram, to investigate the effects of plant population and sett size on biomass accumula tion and quality in white yam (Dioscorea rotundata Poir.) intercropped with coconut (Cocos nucifera L.). Heaviest sett (300 g) planted at the widest spacing (90 cm x 90 cm) promoted the canopy growth. Tuber dry biomass pro duction and total plant dry biomass production were highest in the closest spacing, 60 cm x 60 cm, that accommo dated 20,000 plantstha. Efficient allocation of photo assimilates for storage in tuber was favoured by the widest spacing, 90 cm x 90 cm, resulting in highest mean tuber weight and harvest index. Total biomass production, bio mass accumulation in tubers as well as its partitioning ratio to tubers were notably higher with 300 g setts. Wider spacing (90 cm x 90 cm) also produced better quality tubers by accumulating more starch in tubers, while sett size did not alter tuber quality.