Shoot Nutrient Uptake Research Articles

Fertigation frequency is a useful tool for nitrate management in intensive open-field agriculture

The main source of nitrogen for most cultivated plants is nitrate. Agriculture has overused this nutrient, resulting in serious environmental problems in various parts of the world. The common practice in open intensive horticultural fields with clay-loam soils with a high water retention capacity (e.g., high percentage of clay) is to irrigate two to four times per week. Technically and logistically, this is much easier than one or more irrigation events per day. However, the loss of nutrients and water below the root zone may occur, with the consequent loss of efficiency. In this work, two cultivation cycles in an open-field endive crop were carried out under plastic soil mulching. We compared three fertigation strategies based on different frequencies of fertigation events; low fertigation frequency (LF, two to three fertigation events per week that simulates common farmer practice), medium fertigation frequency (MF, one fertigation event per day), and high fertigation frequency (HF, three fertigation events per day). The three fertigation strategies applied equal water and fertilizers doses per week. The high fertigation frequency increased volumetric water content in the upper soil profile, while the low fertigation frequency in the lower soil profile. The results demonstrated that HF fertigation increases shoot fresh weight (harvest yield) by increasing shoot water content, but did not improve shoot nutrient uptake or nitrogen nutritional status. The important finding, from the environment point of view, is that high and medium fertigation frequencies decreased nitrate concentration in the root influence zone, where it may be prone to leaching due to heavy rain events.

Farmyard manure and arbuscular mycorrhiza fungi inoculation enhanced growth and fruit fibre productivity of Calotropis procera in semi-arid eastern Kenya

A greenhouse experiment was conducted at the South Eastern Kenya University (SEKU) to determine the effects of farmyard manure (FYM) and arbuscular mycorrhiza fungi (AMF) inoculation on growth, vigor, shoot nutrient uptake (SNU) and AMF root colonization percentage (RC%) of potted Calotropis procera (Calotropis) seedlings. A field trial was laid out to determine the effects of the treatments on growth and fruit fibre productivity of the transplanted seedlings. The experiments were laid out in a split-split-plot design with a 2*2*2 factorial arrangement and 3 replications. The main plot factor constituted 2 Kenyan Calotropis provenances, Kibwezi and Tharaka. The sub-plot factor comprised of FYM and without FYM application while the sub-sub-plot factor involved inoculation with mixed strains of commercial AMF and without inoculation. Farmyard manure (FYM) and the integration of FYM and AMF inoculation (FYM*AMF) significantly improved Calotropis seedlings’ growth, vigor, SNU and AMF RC% in the greenhouse. However, FYM*AMF was comparatively superior to solely FYM and AMF. There were positive correlations of AMF RC% with growth, shoot dry weight (SDW) and SNU of the seedlings at the end of the greenhouse experiment. Under field conditions, FYM and FYM*AMF significantly enhanced growth and fruit fibre productivity of Calotropis plants than the controls, barring a few cases. The study recommends the use of FYM and FYM*AMF in Calotropis seedlings’ production in the drylands of Kenya. Future research should investigate the persistence of the introduced commercial AMF strains in the soil using molecular techniques.

Oil radish, winter rye and crimson clover: root and shoot performance in cover crop mixtures

Abstract Purpose The current knowledge of belowground interactions in intercropping systems is limited due to methodological constraints. The current study aimed to investigate cereal-brassica and cereal-legume-brassica cover crop mixtures regarding mixture effects on root and shoot biomass as well as root traits, vertical root niche differentiation, and complementarity. Methods Sole crops and two- and three-species-mixtures of winter rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and oil radish (Raphanus sativus L. var. oleiformis Pers.) were grown in Germany in a two-year organic field experiment. Root traits were analysed using the monolith method. For discrimination of species root mass Fourier transform infrared (FTIR) spectroscopy was used. Results Oil radish dominated mixtures above- and belowground. Oil radish and its mixtures had highest root length density (RLD) and root mass density (RMD) in subsoil. Rye had highest root biomass and RLD in topsoil. Clover was uncompetitive and had low RLD and RMD. Large but non-significant mixture effects occurred in the shoot, especially for shoot nutrient uptake. Mixture effects were positive for RLD and RMD in subsoil and positive for specific root length (SRL) throughout the whole profile. There was no clear evidence for vertical root niche differentiation and root mass complementarity. Conclusion Oil radish as a mixing partner increased rooting in subsoil. When comparing mixtures and sole crops, morphological changes, i.e. higher SRL in mixtures, were found. Contrary to expectations, changes in root allocation patterns, such as vertical niche differentiation or complementarity of root mass, were not observed.

The alleviation of drought-induced damage to growth and physio-biochemical parameters of Brassica napus L. genotypes using an integrated approach of biochar amendment and PGPR application

AbstractDrought is a major abiotic stress, affecting the metabolism, growth, and productivity of plants worldwide. Therefore, this study aimed/hypothesized to investigate the ameliorative effects of biochar and rhizobacteria in drought-damaged Brassica napus L. genotypes. The plants were divided into two groups based on the drought stress employment (15 days and 30 days). Both groups were then treated with PGPR, biochar, and their co-application, and the samples were taken from shoots and roots of both genotypes. Our results revealed that the drought resulted in a substantial decline in total flavonoids, phenolics, proteins, peroxidase (POD), superoxide dismutase (SOD), glutathione reductase (GR) as well as nutrient uptake in shoots and roots of both the studied genotypes. Contrarily, sugar and glycine betaine (GB) contents increased in both shoots and roots under drought stress conditions. However, the plants with co-application of biochar and PGPR showed better improvement of nutrient uptake, leaf relative water content (RWC), and growth parameters compared to drought-stressed, control, and the plants with sole biochar and PGPR application. In addition, the co-application of PGPR and biochar produced higher levels of sugar, proteins, flavonoids, phenolic compounds, and enzymatic activities (POD, SOD, GR, and dehydroascorbate reductase (DHAR)) than those that were not treated with biochar and PGPR or treated solely. Relative to Westar genotype, the Punjab sarson showed higher drought tolerance. In conclusion, we suggest that the co-application of biochar and PGPR can be an effective strategy for overcoming the drought-induced damage in plants. Graphical Abstract

Assessment of graphene oxide toxicity on the growth and nutrient levels of white clover (Trifolium repens L.)

Carbon nanomaterials (CNMs) are novel engineered nanomaterials and have been used widely. Their toxic effects on terrestrial plants in soil matrix require careful investigation. In this study, white clover (Trifolium repens L.) was grown in a potted soil with graphene oxide (GO) at levels of 0.2%, 0.4% and 0.6% and the effects of GO on the growth and nutrient uptake of white clover were evaluated after 50 and 100 days of exposure. GO exposure showed adverse effects on seedling growth, photosynthetic parameters and nutrient uptake in shoots, and the effect was more significant with increasing concentration and exposure time. Compared with the control, GO at the highest level of 0.6% decreased plant height, leaf and stem dry weights, total chlorophyll content and net photosynthetic rate by 43.7%, 45.7%, 43.4%, 32% and 85.7%, respectively, after 100 d of exposure, and N, K, Cu, Zn, Fe, Mo, B, Si contents decreased by 19.5%, 20.1%, 12.6%, 25.0%, 12.9%, 26.0%, 18.9%, 23.0%, respectively. Furthermore, the electrolyte leakage, lipid peroxidation, reactive oxygen species, antioxidant enzyme activities were all increased by GO, especially at high dose and long exposure. These results indicate that GO can suppress plant growth by oxidative stress, photosynthesis inhibition, and nutrient imbalance.

Effect of ridge film mulching and nitrogen application rate on seed quality, oil yield and nitrogen-use efficiency of winter oilseed rape in northwest China

ABSTRACT Three-year field experiments were conducted to investigate the effects of ridge film mulching plus furrow planting (RFMF) and traditional flat planting (FP) on the seed quality, oil yield and nitrogen-use efficiency of winter oilseed rape (Brassica napus) and to determine the optimal rate of nitrogen (N) application under the two planting patterns. Six N rates, 0, 60, 120, 180, 240 and 300 kg N ha−1, were applied under both patterns. RFMF significantly increased seed yield, oil yield, N agronomic efficiency (NAE) and N partial factor productivity (NPFP) by 15.5–43.5%, 18.0–48.3%, 2.1–70.6% and 17.9–48.2% respectively, compared with FP. The optimal N application rates were 235 and 218 kg N ha−1 under RFMF and FP, respectively. In conclusion, RFMF could be adopted with N rate of 235 kg N ha−1 for the cultivation of winter oilseed rape in northwest China to improve shoot nutrient uptake, oil yield and N use efficiencies.

Variation of Cicer Germplasm to Manganese Toxicity Tolerance.

After aluminum, manganese toxicity is the most limiting factor for crops grown in acidic soils worldwide. But overall, research on Mn toxicity is still limited. The poor acid tolerance of chickpea may be related to Mn toxicity, but there has been no previous screening of chickpea germplasm (nor in its wild Cicer relatives, Cicer reticulatum and Cicer echinospermum) for tolerance to Mn toxicity. A screening technique was developed for tolerance to Mn toxicity using three released cultivars of chickpea (Cicer arietinum L), Ambar, PBA HatTrick, and PBA Striker; one accession each of C. reticulatum and C. echinospermum; and lupin (Lupinus angustifolius) as a Mn-tolerant check, with eight Mn concentrations of 2, 25, 50, 100, 150, 200, 250, and 500 μM Mn as MnSO4 in a low-ionic-strength nutrient solution. The plants were harvested at 14 and 28 days after Mn treatments. The nutrient uptake in shoots (young, old leaves, and the rest of the shoot) and roots was investigated. The best discrimination between tolerant and intolerant Cicer genotypes based on relative shoot dry weight, root dry weight, total root length, and scoring of toxicity symptoms was achieved at 150 μM Mn after 14 days of growth in Mn solution. Among the chickpea cultivars, the greater relative plant growth (both shoot and root) of Ambar and PBA Striker at 100–200 μM Mn contrasted with that of PBA HatTrick, while the C. echinospermum accession was more tolerant to Mn toxicity than C. reticulatum. Manganese tolerance in both domestic cultivars and wild accessions was associated with internal tolerance to excess Mn following greater uptake of Mn and translocation of Mn from roots to shoots.

Influence of PGPR-enriched liquid organic fertilizers on the growth and nutrients uptake of maize under drought condition in calcareous soil

In order to study the effect of water deficit stress (WDS), plant growth promoting rhizobacteria (PGPR)-enriched and non-enriched vermicompost tea(VT) and vermiwash(V) on the growth and nutrients uptakes of maize, a greenhouse experiment was conducted. The two-factor experiment was set up in a completely randomized design with three replications. The factors included: 1) liquid organic fertilizers (LOFs) with five levels (control, VT, V, vermicompost tea enriched with bacterium (VTB) and vermiwash enriched with bacterium (VB)) and 2) WDS with three levels (Field Capacity (FC), 80% FC and 60% FC(. At each irrigation interval, the volume of the used LOFs was equivalent to 60% of the volume of water required for 60% FC. At 60% FC, shoot dry matter (SDW), shoot N, P, Zn, Cu, and Fe uptake significantly decreased compared with those of FC and 80% FC, whereas shoot K uptake significantly increased. At all WDS levels, application of LOFs led to increase in SDW and shoot nutrients uptake. The highest amount of studied traits was obtained in VTB and VT treatments. Generally, VT treatments were more effective than V. Furthermore, PGPR-enriched LOFs were more effective than non-enriched ones. Application of LOFs may be considered as a practical approach for amplifying drought tolerance and reducing the risk of water scarcity in maize cultivation.

Enhanced Ni phytoextraction by effectiveness of chemical and biological amendments in sunflower plant grown in Ni-polluted soils

ABSTRACTA greenhouse study was conducted as a completely randomised design in a factorial arrangement to assess how inoculation of AMF (arbuscular mycorrhizal fungus) and application of EDTA (ethylenediaminetetracetic acid) as biological and chemical amendments can affect the Ni (nickel) phytoremediation in Ni-polluted soils using sunflower plant. The results showed that the inoculation of AMF increased root colonisation while applying EDTA and high level of Ni decreased it. Microbial incubation has a positive effect on both shoot and root dry yields; however, co-application of Ni and EDTA demoted the growth rate. Shoot nutrients uptake of plants decreased as Ni levels increased. In inoculated plants, shoot uptake of Zn, Fe and Mn was higher in all Ni levels than non-inoculated plants. Ni uptake in plant shoots and roots increased with applying both AMF and EDTA. However, the mean Ni concentration and uptake in inoculated plants along with applying EDTA are higher in sunflower shoots than in roots. As Ni levels increased, Ni extraction and uptake efficiencies increased; it can be concluded co-application of EDTA and AMF was effective in increasing phytoextraction potential of sunflower plants in Ni-contaminated sites. This study highlights that AMF could be suitable for cleaning Ni-polluted areas and it could significantly contribute to phytoremediation technology.

The effects of arbuscular mycorrhizal fungus and water stress on some antioxidant enzymes activities and nutrients uptake of two citrus rootstocks

ABSTRACT-Water stress is the main cause for crop yield reduction in the majority of agricultural regions of the world because it affects almost all plant functions. The effects of Glomus mosseae on growth, nutrients uptake, and antioxidant enzymes of sour orange (Citrus aurantium) and rough lemon) Citrus jambheri) rootstocks were assessed in sterilized soil under greenhouse conditions. A three-factor experiment was set up in a completely randomized design with three replicates of each treatment. Treatments consisted of water stress at four levels (irrigation intervals of 2, 4, 6, and 8 days) and mycorrhizal treatments at two levels (inoculation with G. mosseae and non-mycorrhizal control). Mycorrhizal seedlings of two citrus rootstocks were successfully infected by G. mosseae. As water stress increased, root colonization, shoot dry weight, shoot N, P, Mn, Cu, and Fe uptake of two citrus rootstocks significantly decreased but shoot Zn uptake and the antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (G-POD) and ascorbate peroxidase (APX)] activities of two citrus rootstocks leaves increased. With inoculation of seedlings by G. mosseae compared with control, shoot dry weight, N and P uptake, and antioxidant enzymes activities increased. It may be concluded that mycorrhizal inoculation notably influenced shoot nutrients uptake and leaves antioxidant enzymes activities in citrus and an increase in these parameters alleviated water stress.

Effects of plant growth-promoting rhizobacterium (PGPR) and arbuscular mycorrhizal fungus (AMF) on antioxidant enzyme activities in salt-stressed bean (phaseolus vulgaris l.)

Abstract Plant Growth-Promoting Rhizobacterium (PGPR) represents a wide variety of soil bacteria that, when grown in association with a host plant, result in stimulation of growth of their host. The aim of this study was to investigate the influence of inoculation with a PGPR, Pseudomonas fluorescence, alone or in combination with an arbuscular mycorrhizal fungus, Glomus mosseae (Nicol. & Gerd.), on antioxidant enzyme activities (catalase (CAT) and peroxidase (POX)), phosphatase activity, solutes accumulation, growth and minerals nutrient uptake in shoots of bean (Phaseolus vulgaris L.) affected by three levels of salt stress. Salinity decreased bean growth, regardless of the biological treatment and the salt stress level. The plants inoculated with P. fluorescence had significantly greater shoot biomass than the control plants at all salinity levels, whereas the mycorrhizal inoculation treatments were only effective in increasing shoot biomass at a low salinity level. The plants inoculated with P. fluorescence presented higher concentrations of shoots’ K+ and lower concentrations of shoots’ Na+ under high salt conditions. Salt stress increased shoots’ proline concentration, particularly in plants inoculated with the PGPR. Increasing salinity stress raised significantly the antioxidant enzyme activities, including those of total POX and CAT, of bean shoots compared with their corresponding nonstressed plants. The PGPR strain induced a higher increase in these antioxidant enzymes in response to severe salinity. Inoculation with selected PGPR could serve as a useful tool for alleviating salinity stress in salt-sensitive plants.

Bioremediation of Cadmium-Contaminated Soil through Cultivation of Maize Inoculated with Plant Growth–Promoting Rhizobacteria

ABSTRACT A pot experiment was conducted to study the effect of single and co-inoculation of Bacillus mycoides and Micrococcus roseus strains, indigenous to heavy metal (HM)–contaminated soils, on the growth and essential-nutrient and Cd uptake of maize in a soil polluted with 100 and 200 mg Cd kg−1. Increasing Cd levels significantly decreased shoot and root dry weights, and shoot P, Fe, Zn, and Mn uptake. All bacterial treatments significantly increased biomass and shoot nutrient uptake of plant compared with control in the soil polluted with Cd. Inoculation of plants with B. mycoides and consortium of two bacteria significantly increased, whereas M. roseus significantly decreased, shoot and root Cd uptake, and Cd transfer and translocation factors compared with control in Cd-polluted conditions. The results showed that B. mycoides and consortium of two bacteria had an effective role in phytoextraction and M. roseus was the most effective treatment in phytostabilization of Cd.

Morphological and physiological variation among seagrass (Zostera marina) genotypes

Intraspecific variation in habitat-forming species can have important ecological consequences at the population, community, and ecosystem level. However, the contribution of genetic variation among individuals to these effects is seldom documented. We quantified morphological and physiological variation among genotypes of a marine foundation species, the seagrass Zostera marina. We grew replicate shoots of eight genetically distinct Zostera individuals collected from Bodega Bay, California, in a common garden environment and then quantified shoot production and morphology, nutrient uptake, and key photosynthetic parameters. We found that genotypes differed in shoot production, biomass, and both root and shoot nutrient uptake rates, even when corrected for genotype-specific biomass differences. In addition, the rank order of uptake ability differed for ammonium and nitrate, indicating that genotypes may exhibit resource partitioning of different forms of nutrients. Our results suggest that both niche complementarity among genotypes and the sampling/selection effect could contribute to previously observed positive effects of seagrass clonal diversity on resource utilization and biomass production. Further, they highlight that genotypic variation in key traits of habitat-forming species could have measurable effects on community structure and function.

Effects of arbuscular mycorrhiza, soil sterilization, and soil compaction on wheat ( Triticum aestivum L.) nutrients uptake

The stress of soil compaction, because of using agricultural machinery, may provide conditions such as limiting nutrient uptake, not suitable for plant growth. Here we hypothesized that using arbuscular mycorrhiza (AM, plant symbiotic fungi), as a biological method, may overcome the stress of soil compaction on wheat ( Triticum aestivum L.) growth by enhancing nutrient uptake. Soil surface layer of the Experimental Research Field of Soil and Water Research Institute in Karaj, Iran, was sieved, sterilized, and compacted at 10 kg pots in two experiments. At seeding wheat seeds were inoculated with different species of Glomus fungi with different origins. Shoot nutrient uptake of N, P, K, Fe, Mn, Zn, Cu was determined. Soil sterilization significantly increased the nutrient uptake of mycorrhizal wheat even at the highest level of compaction. Even under compacted conditions, increased P uptake, due to AM inoculation had an important role to alleviate the stress. This novel finding may indicate the important role of AM to overcome the stress of soil compaction on wheat nutrient uptake, the independency of AM origin on their functionality, and the great importance of managing soil biological communities in agricultural systems.

Cadmium phytoextraction capacity in eight C3 herbage grass species

AbstractGrasses are excellent candidates for phytoremediation because of their high biomass production, high adaptability and low management cost. This study assesses interspecific variation of cadmium (Cd) phytoextraction capabilities in eight C3 grass species. Populations of 30‐day‐old C3 grass species – namely, Agrostis alba, Anthoxanthum odoratum, Dactylis glomerata, Festuca arundinacea, Festuca pratensis, Lolium multiflorum, Lolium perenne and Poa pratensis– were grown hydroponically for 15 days with different concentrations of Cd (0, 5, 10 and 50 µM). For each species, shoot biomass, the proportion of growth inhibition (GI, %), shoot Cd concentration and accumulation, shoot nutrient uptake, and the proportion of uptake inhibition (UI, %) of nutrient minerals were evaluated. Effects of Cd application included stunted growth. The GI increased from 5% to 70% with an increase in Cd concentrations. For all Cd treatments, L. multiflorum showed the highest shoot dry biomass. Shoot Cd concentrations negatively affected mineral nutrient uptake. The highest Cd treatment caused UI of various elements of 37–95%. Under 50‐µM Cd treatment, Cd accumulation varied by 20 times among species, and L. multiflorum showed the highest Cd accumulation (116.46 µg plant−1). Our results indicate that L. multiflorum exhibited high degrees of both Cd tolerance and Cd phytoextraction capacity among grass species.

Ecological strategies of ectomycorrhizal fungi of Salix repens: root manipulation versus root replacement

The ecological significance of a range of ectomycorrhizal fungal species, associated with Salix repens, was investigated under controlled conditions. Different ectomycorrhizas increased plant benefits in various ways. Effects of 12 ectomycorrhizal fungi on short‐term (12 weeks) and long‐term (20 and 30 weeks) plant performance were compared. Different fungi increased plant benefits in different ways and none exerted the full range of mycorrhizal benefits. Two strategies of EcM fungi were recognized, root manipulation and root replacement. Species (Hebeloma, Cortinarius spp.) with a root manipulation strategy strongly increased root length and had a more effective nitrogen economy than species with the root replacement strategy (Laccaria, Paxillus spp.). As a consequence of these different strategies two parameters of nutrient acquisition, viz. nutrient inflow per unit root length (efficiency) and total shoot nutrient uptake (effectiveness) were not correlated. Differences in magnitude of mycorrhizal response were not related to the amount of root colonization. Only in the short term was plant nutrient content positively correlated with root length colonized. Over a whole growing season plant nutrient content could not be predicted from root length colonized. Effects of mycorrhizal fungi on root manipulation also occurred with aqueous extracts of the fungus and, hence, were partly independent of the formation of ectomycorrhizas.

Plant Growth, Mycorrhizal Association, Nutrient Uptake and Phosphorus Dynamics in a Volcanic-Ash Soil in Colombia as Affected by the Establishment of Tithonia diversifolia

ABSTRACT Tithonia diversifolia has the ability to sequester nutrients from soil in its tissues, including P, and has been shown to be useful for cycling nutrients via biomass transfer and improved fallow. We investigated the effects of its establishment from bare root seedlings (plantlets) and vegetative stem cuttings (stakes) on shoot and root growth characteristics, arbuscular-mycorrhizae (AM) associations, nutrient acquisition and utilization, and P dynamics in a fine-textured volcanic-ash soil (Oxic Dystropept) of a mid-altitude hillside in southwestern Colombia. One year after establishment, the following determinations were made: leaf area index; shoot and root N, P, K, Ca, and Mg acquisition; AM root infection; AM fungal spores per 100 g soil; soil chemical characteristics; and P fractionation into inorganic (Pi) and organic (Po) pools. AM root infection in both coarse and fine roots was significantly greater in plants established from plantlets than those established from stakes with differences of 21 and 31%, respectively. Nutrient uptake efficiency (μg of shoot nutrient uptake per m of root length) and use efficiency (g of shoot biomass produced per g of shoot nutrient uptake) for N, P, K, Ca, and Mg were also greater with plants established from plantlets than those established from stakes. Improved nutrient acquisition could be attributed to relief from P stress and possibly uptake of some essential micronutrients resulting from AM association. High soil variability masked the effect of the establishment method on phosphorus pools, and neither the biologically available P (H2O-Po, resin-Pi, and NaHCO3-Pi and -Po) nor the moderately resistant P (NaOH-extractable P) was significantly affected, although plantlets had higher values. This study has shown that on this soil when Tithonia is to be used as a fallow species, the use of plantlets as compared to the stake method of establishment is better for nutrient acquisition and recycling.

Fertiliser use efficiency by containerised nursery plants. 3. Effect of heavy leaching and damaged fertiliser prills on plant growth, nutrient uptake, and nutrient loss

Nutrient leaching loss, plant growth, and nutrient uptake of 4-week (transplanting to sale) ground-cover species were investigated under a range of leaching conditions and with different sources of a controlled- release fertiliser (CRF), Osmocote NPK (3–4 month) (Osm). Osm was applied pre-planting at a rate equivalent to 800 g N/m3 to pots containing sand, and composted pinebark and hardwood sawdust medium that had received nutrient amendment during formulation. Two experiments were conducted in a glasshouse over summer–autumn where irrigation treatments produced defined leachate volumes. In Expt 1, leachate volumes of <5, 50, and 200 mL every 2 days each received an additional single heavy leaching event of 400 mL after 1, 2, or 3 weeks. In Expt 2, the 3 leachate volumes were each fertilised with new Osm (a newly purchased Osm) or old Osm (a 2-year-old source), where both of these sources contained 0.5–1.5% visibly damaged prills; and damaged Osm, where damaged prills were used exclusively. In both experiments, increasing leachate volume increased (P < 0.001) leaching of N (nitrate + ammonium), P, K, Ca, and Mg. In Expt 1, leaching was highest (P < 0.01) when the heavy leaching event occurred after 2 or 3 weeks for N and after 2 weeks for P. When damaged Osm was used, N, P, and K loss was 3–15 times higher (P < 0.001) than from new and old Osm (98.5–99.5% undamaged). The highest leaching loss of N, P, K, Ca, and Mg occurred in the first week after potting up, with damaged prills at highest leaching volume. Increasing leachate volume (in the presence of a heavy leaching event) reduced (P < 0.001) electrical conductivity (EC) of potting medium after 4 weeks from 1.02 to 0.54 dS/m. Damaged prills reduced (P < 0.001) EC at the high leachate volume in relation to new Osm (2.38 v. 0.29 dS/m). Treatments that increased (P < 0.05) nutrient leaching generally reduced (P < 0.05) nutrient concentrations in shoots and depressed the growth of some plant species. Shoot growth of 2 of 5 species was reduced (P < 0.001) at the highest leachate volume with an additional heavy leaching event in Week 1 or 2, and root growth of all but the slowest growing species declined with increasing leachate volume. Damaged prills reduced (P < 0.001) shoot growth of 2 of the 5 ground-cover species. This study demonstrated that excessive leaching and the use of damaged prills for containerised nursery plants fertilised with CRF results in high nutrient loss, low residual nutrient content, reduced nutrient uptake in shoots, and reduced shoot growth of some species.

Differences in tolerance to infertile acid soil stress among germplasm accessions and genetic recombinants of the tropical forage grass genus, Brachiaria

Several Brachiaria species are the most widely grown forages in tropical America. A field study was conducted during two seasons (1994, wet and 1995, dry) in a medium-textured Oxisol at Carimagua, Colombia. The main objective of the study was to evaluate genotypic variation in plant attributes for tolerance to low fertility, acid soil stress conditions (pH 4.9) among germplasm accessions and genetic recombinants of Brachiaria. The entries included 43 genetic recombinants selected from a breeding population, four parental accessions and an additional eight germplasm accessions. Small amounts of fertilizer were applied at establishment (kg ha −1: 40 N, 20 P, 20 K, 14 Ca, 12 Mg and 12 S). A number of plant attributes including forage yield, leaf area, shoot nutrient composition and shoot nutrient uptake were measured during both seasons. Significant genetic variation was observed in several plant attributes such as leaf area, shoot nutrient content, nutrient partitioning to leaves, shoot nutrient uptake, and forage yield in both seasons. Forage yield ranged from 59 to 343 g plant −1 in the wet season and 5 to 174 g plant −1 in the dry season. Correlation between forage yield and shoot nutrient uptake indicated the importance of nutrient acquisition, particularly of phosphorus ( r=0.90; P<0.0001), for adaptation to infertile acid soil stress. Two genetic recombinants (BRN093/3009, FM9201/1873) were productive when grown under infertile acid soil stress in both wet and dry seasons. But, neither of these two recombinants is highly resistant to xylem-feeding insects known as spittlebugs (Homoptera: Cercopidae). One spittlebug-resistant genetic recombinant (BRN093/1371) exhibited several desirable attributes such as superior leaf area and leaf biomass, greater N content in leaves, and greater partitioning of N and P to leaves that could contribute to adaptation and persistence in these soils. This recombinant is being utilized in a breeding program to develop superior Brachiaria lines.

Adaptive attributes of tropical forage species to acid soils I. Differences in plant growth, nutrient acquisition and nutrient utilization among C4grasses and C3legumes

Abstract Low supply of nutrients is a major limitation of forage adaptation and production in acid soils of the tropics. A glasshouse study was conducted to find differences in plant growth, nutrient acquisition and use, among species of tropical forage grasses (with C4 pathway of photosynthesis) and legumes (with C3), when grown in two acid soils of contrasting texture and fertility. Twelve tropical forage legumes and seven tropical forage grasses were grown in sandy loam and clay loam Oxisols at low and high levels of soil fertility. After 83 days of growth, dry matter distribution among plant leaves, stems, and roots, leaf area production, shoot and root nutrient composition, shoot nutrient uptake, and nutrient use efficiency were measured. Soil type and fertility affected biomass production and dry matter partitioning between roots and shoots. The allocation of dry matter to root production was greater with low soil fertility, particularly in sandy loam. The grasses responded more than the legumes to ...