High Fertilizer Rates Research Articles

Fertilizer, Irrigation, and Natural Ericaceous Root and Soil Inoculum (NERS): Effects on Container-grown Ericaceous Nursery Crop Biomass, Tissue Nutrient Concentration, and Leachate Nutrient Quality

We tested the effects of using an inoculum containing natural ericoid roots and soil (NERS) with two fertilizer and irrigation rates on plant growth, shoot (stems and leaves) nutrient concentration, leachate quality, and mycorrhizal colonization of container-grown Coast Leucothoe [Leucothoe axillaris (Lam.) D. Don] and Japanese Pieris [Pieris japonica (Thunb.) D. Don ex G. Don]. Uniform rooted liners were grown in 10.8-L containers in a pine bark, peatmoss, and sand (8:1:1 by volume) substrate medium in a randomized complete block design with four replications. A controlled-release fertilizer, Polyon® Plus 14-16-8 (14N–7P–6.6K), was incorporated in the substrate medium at the 100% manufacturer's recommended fertilizer rate [representing high fertilizer rate (HF)] (56 g per container) to supply 7.84 g nitrogen (N) and at 50% the manufacturer's recommended rate [representing low fertilizer rate (LF)]. Plants were irrigated using a cyclic drip irrigation system at high (HI) and low (LI) irrigation rates calibrated to supply 25.2 L of water and 16.8 L per week, respectively. On average, NERS inoculation increased shoot growth of Leucothoe and Pieris by 56% and 60%, respectively. Shoots of Leucothoe inoculated with NERS had higher N, phosphorus (P), magnesium (Mg), and manganese (Mn) concentrations than non-inoculated plants. At LF, nitrous-N (NOx-N) and orthophosphorus (PO4-P) concentrations in the leachate were reduced by 53% from Leucothoe and 62% from Pieris compared with HF-treated plants. A reduction of 37% and 36% in PO4-P concentration in leachates from Leucothoe and Pieris, respectively, were achieved at the reduced irrigation (LI) rate. The NERS inoculation reduced PO4-P concentrations in leachate from Leucothoe by 26% and NOx-N concentration by 33% in leachates from Pieris compared with non-inoculated plants. Compared with plants grown in the HI–HF treatment, the combination of LI–LF treatment reduced NOx-N concentrations in leachates from Leucothoe by 60% (P = 0.016) and reduced PO4-P leachate concentrations from Pieris by 72% (P = 0.0096). Decreasing the fertilizer rate to 50% of the recommended rate and the irrigation rate to 67% of the recommended rate in conjunction with the incorporation of NERS reduced leachate nutrient concentrations of two main water pollutants (NOx-N and PO4-P). Adopting the practice of adding NERS containing fungi and bacteria can be an effective system to increase shoot dry weight, allow reduction in fertilizer application, conserve water for irrigation, and minimize subsequent nutrient runoff in nursery operations.

Improving Nutrient-Use Efficiency in Chinese Potato Production: Experiences from the United States

Potato (Solanum tuberosum L.) is the fourth most important food crop in the world after corn, wheat, and rice. It is adapted to a wide range of growing conditions, producing high yields with a near-optimum balance of nutrients for human consumption. China is the world's largest potato producer and continues to account for a large part of the global increase in potato production. Although the potato can be highly productive, it has a relatively shallow root system and often requires significant nutrient inputs to maintain tuber productivity and quality. Each metric ton of tubers removes approximately 3.8 kg nitrogen (N), 0.6 kg phosphorus (P), and 4.4 kg potassium (K). Proper nutrient management, therefore, is extremely important for sustaining high tuber yield and quality. Lack of adequate balanced fertilization in China is reportedly a yield-limiting factor in some areas. For example, potassium (K) is very important for producing a potato crop with high tuber yield and quality. Limited K resources in China and continued cropping have resulted in below-adequate levels of soil K in many regions of the country, which will impact potato production. On the other hand, based on U.S. experience, the high nutrient demand by potato, application of high rates of fertilizer, and production on coarser textured soils can result in nutrient losses. Nutrient best-management practices are developed with the objective of optimizing production, net returns, and minimizing environmental degradation. In general, optimal N management has had the most important impact on tuber yield and quality compared with the other essential elements. Best management practices for N fertilization include appropriate selection of rate, source, timing, and method of application. Optimal management of irrigation is also important to improve N-uptake efficiency and minimize N losses while maintaining high yields and quality. Phosphorus is another key nutrient important from both production and environmental standpoints. Adequate P is required for optimum tuber-set, while excessive rates may result in soil-P buildup and potential runoff problems. This review will focus on various management techniques to maximize nutrient-uptake efficiency by potatoes.

The effect of different tillage-fertilization practices on the mycoflora of wheat grains

A two-factor field experiment was carried out at the Lithuanian Institute of Agriculture during the period 2005-2008. The influence of different tillage and fertilization practices on wheat grain fungal contamination was evaluated. Grain surface contamination and internal grain infection with fungi were quantified using agar tests. Purified colonies were identified using different manuals. A total of 16 fungal genera were identified in spring and winter wheat grains. Alternaria infected 46.3% - 99.9%, Cladosporium 26.9% - 77.8%, Fusarium 0.9% - 37.1%, Penicillium 1.3% - 2.5% of grains tested. Winter wheat grain surface contamination by fungi ranged from 7.2 × 103 to 24.8 × 103 of colony forming units per g of grain (cfu g-1), spring wheat from 14.8 × 103 to 80.3 × 103 cfu g-1. No-tillage increased winter wheat grain infection by Alternaria, Aspergillus and Cladosporium species and total count of cfu g-1 on spring wheat grain surface. High fertilizer rates resulted in an increase in spring wheat grain infection by Fusarium and Penicillium species and total count of cfu g-1 on both spring and winter wheat grain surface.;

Effects of Elevated CO2 and O3 and N Fertilization on Amount of Soil Microbial Biomass Carbon in Spring Wheat Growing Season

Experimental platform of Open-top chambers (OTC) was established in 2006 over a spring wheat system, it located at the National Field Observation and Research Station of Shenyang Agro-ecosystems, a member of Chinese Ecosystem Research Network (CERN) established in 1987. We compared the dynamics of soil microbial biomass C with high (225.0kg N hm-2) and low (150kg N hm-2) application rate of chemical fertilizer N exposed to the elevated CO2, O3, CO2 plus O3 and CK after the spring wheat growing season in 2010. The results showed that under elevated CO2 concentration at the jointing stage, high application rate of chemical fertilizer N significantly declined the amount of soil microbial biomass C by 64.97%, compared with the low N application rate of chemical fertilizer N (p<0.01). In treatment with low application rate of chemical fertilizer N, elevated O3 concentration significantly declined the amount of soil microbial biomass C by 52.49% (p<0.05), compared with CK. In treatment with high application rate of chemical fertilizer N, the interaction of CO2 and O3 increased significantly the amount of soil microbial biomass C by 50.03% (p<0.05), compared with CK. At the ripening stage, under elevated CO2 concentration and interaction of CO2 and O3, high application rate of chemical fertilizer N significantly decreased the amount of soil microbial biomass C by 32.92% and 41.45%, compared with low N application rate of chemical fertilizer N, respectively (p<0.05). In treatment with low application rate of chemical fertilizer N, elevated CO2 and interaction of CO2 and O3 significantly increased the amount of soil microbial biomass C by 25.32% and 38.59% (p<0.05), compared with CK, respectively.

Fertilization and allelopathy modify Pinus halepensis saplings crown acclimation to shade

Pinus halepensis Mill., is a Mediterranean pioneer forest species with shade-intolerant features. The purpose of this study is to better understand how stand fertility and allelopathic properties of adult trees influence shade acclimation of saplings. Crown growth and morphological plasticity were studied under different light, fertilization, and allelopathic conditions in a nursery experiment. We tested whether shade-acclimation capacity increases with fertilization, and is affected by autotoxicity due to pine leachates. We examined stem diameter, and crown characteristics (length, width, shape, and density) in a factorial experiment with two levels for each tested factor: light (full and 20% reduced light), fertilization (low and high rate of NPK fertilizer) and allelopathy (control and allelopathic leachates uptake). In our study, shading induced a significantly higher crown length, width, and surface. Fertilization strongly increased crown length and vertical expended crown shape (the ratio crown length/crown width). Leachates uptake reduced crown length and density, highlighting an autotoxicity phenomenon. We concluded that P. halepensis saplings presented a shade-avoiding syndrome and that the crown shade-acclimation response increased with fertilization but was severely compromised by autotoxicity. We finally discuss the role of fertilization and allelopathy in early P. halepensis acclimation ability.

Nitrogen washing from C3 and C4 cover grasses residues by rain

Crop species with the C4 photosynthetic pathway are more efficient in assimilating N than C3 plants, which results in different N amounts prone to be washed from its straw by rain water. Such differences may affect N recycling in agricultural systems where these species are grown as cover crops. In this experiment, phytomass production and N leaching from the straw of grasses with different photosynthetic pathways were studied in response to N application. Pearl millet (Pennisetum glaucum) and congo grass (Brachiaria ruziziensis) with the C4 photosynthetic pathway, and black oat (Avena Strigosa) and triticale (X Triticosecale), with the C3 photosynthetic pathway, were grown for 47 days. After determining dry matter yields and N and C contents, a 30 mm rainfall was simulated over 8 t ha-1 of dry matter of each plant residue and the leached amounts of ammonium and nitrate were determined. C4 grasses responded to higher fertilizer rates, whereas N contents in plant tissue were lower. The amount of N leached from C4 grass residues was lower, probably because the C/N ratio is higher and N is more tightly bound to organic compounds. When planning a crop rotation system it is important to take into account the difference in N release of different plant residues which may affect N nutrition of the subsequent crop.

Accumulation of nitrate N in the soil profile and its implications for the environment under dryland agriculture in northern China: A review

Nitrate (NO3-) leaching and water contamination have become a worldwide concern. In this review, some examples are presented to show the extent and magnitude of NO3- accumulation in the soil profiles and its potential effects on contamination of ground water and surface water under dryland farming in northern China. Climatic and management factors affecting NO3- leaching are also discussed. In northern China, rainfall is relatively sparse, but the high intensity of precipitation and porous soils play an important role in the accumulation of NO3N in soil and its subsequent leaching in the soil profile. There is a risk of nitrate accumulation and leaching when high rates of fertilizer N are applied to improve crop yields, and it becomes even worse when conventional land use is changed from cereal crops to vegetable crops and fruit orchards. Under such conditions, shallow ground water might be polluted by NO3-. This suggests that more attention should be paid to prevent this problem by using best management practices, especially by controlling the amount of N fertilizer input, balanced fertilization, split N application, inclusion of crops with deep taproots in the rotation and minimizing summer fallow (especially tilled) frequency. Key words: Accumulation, contamination, dryland farming, ground water, leaching, nitrate, northern China

MORPHO-PHYSIOLOGICAL AND ANATOMICAL RESPONSES OF WHEAT PLANTS TO MICRONUTRIENTS AND NITROGEN FERTILIZATION

Two field experiments were conducted in 2005/2006 and 2006/2007 in the region of Tag AL-Ezz, Agricultural Research Station Farm, Dakahlia Governorate, Agricultural Research Center, Egypt to evaluate the effect of nitrogen rates and micronutrients fertilizers on wheat plant growth, some physiological and anatomical parameters and yield. Application of micronutrients combined mixture under high nitrogen rate produced the highest values of plant growth, yield and physiological characteristics compared with other treatments. The second rank best treatment was observed with applications of Zn, then Mn treatment. Cu and Fe treatments were equal in its effect and the differences between them were insignificant in the most cases. Application of nitrogen rate up to 90 kg/fed increased gradually all studied characters. Anatomically, application of combined mixtures of micronutrients under high nitrogen rate increased significantly all anatomical characteristics of flag leaf or culm, in particular, number of vascular bundles and thickness of mechanical tissue in culm as well as dimension of vascular bundles, diameter of metaxylem vessels, and thickness of epidermis in both flag leaf and culm. Furthermore, thickness of mesophyll parenchyma and midrib region in flag leaf was also increased. In conclusion, the obtained results show that foliar application of combined mixture of studied micronutrients (Cu, Mn, Fe and Zn) at the rate of 500 ppm from each under moderate (recommended rate) or high rate of nitrogen fertilizer (70 or 90 kg N/fed) can be recommended to maximize wheat growth and grain yield per main spike and per plant.

EFFECTS OF CONVENTIONAL AND CONTROLLED RELEASE PHOSPHORUS FERTILIZER ON CROP EMERGENCE AND GROWTH RESPONSE UNDER CONTROLLED ENVIRONMENT CONDITIONS

A series of experiments on the effects of form and rate of seed row placed phosphorus (P) fertilizer were carried out under controlled environment conditions using flats of a P-deficient Brown Chernozemic soil from Saskatchewan, Canada. The experiments were conducted in the laboratory and growth chamber using rates of seed row placed granular P fertilizer up to 100 kg P2O5 ha−1. Two forms of monoammonium phosphate fertilizer were compared: 1) conventional MAP granules and 2) controlled release phosphorus (CRP) fertilizer granules (Agrium Inc, Denver, CO, USA.) made with a polymer coating to slow the release of phosphate to soil solution. Six crops were utilized in the study to provide a range of commonly grown cereal, oilseed, pulse and forage crops in Western Canada: wheat (Triticum aestivum), canola (Brassica napus), mustard (Brassica juncea), flax (Linum usitatissimum), yellow pea (Pisum sativum) and alfalfa (Medicago sativum). Parameters measured were percentage of planted seeds that had emerged after two weeks, plant biomass yield, and plant P uptake after four weeks. Most of the crops tested showed no negative impact on emergence with seed row placed conventional P fertilizer at rates up to ∼20 to 30 kg P2O5 ha−1. Pea, flax and mustard tended to be most sensitive to injury from high rates of seed placed MAP while wheat was least sensitive. The controlled release phosphorus fertilizer (CRP) product greatly increased the tolerance of crops to high rates of seed row placed P, with rates of 80 kg P2O5 ha−1 placed in the seed row producing no significant injury for most crops. This effect is attributed to the coating reducing the harmful salt effect that occurs when high rates of fertilizer are placed in the seed row in close proximity to the seed. Generally, a rate of 30 kg P2O5 ha−1 was sufficient to produce maximum early season biomass yield and P uptake for both conventional MAP and CRP fertilizers. Large differences in early P availability were not evident between the conventional P and controlled released P fertilizer products.

Bottom-up control of water hyacinth weevil populations: do the plants regulate the insects?

1. Nutrient availability varies widely in aquatic systems and is likely to profoundly affect the outcomes of plant–herbivore interactions in aquatic environments. This has implications in programmes aimed at the biological control of water weeds. We hypothesized that nutrient flux seasonally affects ovarian development of two specialist weevil species, Neochetina eichhorniae and Neochetina bruchi, thereby influencing population growth on the floating plant Eichhornia crassipes. 2. We also hypothesized that the weevils differed in their sensitivities to nutritional quality and interacted differently depending on host quality. 3. To test these hypotheses, we cultured E. crassipes plants under 20 fertilizer regimens then introduced reproductively dormant, over-wintering female weevils as single or mixed species populations. They were later retrieved and dissected to ascertain ovarian status. F1 progeny was extracted biweekly to compare fecundity with population growth. 4. Ovaries regained functionality and the reproductive proportion of the population increased with fertilizer rate as did the fecundity of reproductive individuals. F1 progeny increased exponentially from 7 to over 300 weevils tank−1 in the highest fertilizer treatment. 5. Mixed species treatments produced more offspring under high fertilizer rates than single species treatments (236 ± 32 mixed vs. 155 ± 25 N. bruchi or 170 ± 33 N. eichhorniae pure). Neochetina eichhorniae was more productive throughout than N. bruchi, but N. bruchi performed nearly as well in high fertilizer treatments. 6. Ratios of the two species remained consistent whether in single or mixed species populations suggesting a lack of interspecific interference. However, N. eichhorniae seemed more adaptable to a wider range of plant quality and more tolerant of lower nutritional circumstances. 7. Synthesis and applications. The coupling of reproductive status of the parental generation with the population response of the F1 generation indicates that plant quality drives population growth of both weevil species, demonstrating bottom-up regulation. This largely explains the variable performance of these weevils as biological control agents. These results emphasize the importance of considering bottom-up regulation in evaluating host range trials, predicting efficacy and in post-release evaluations. In addition, they suggest that partial herbicide treatments to accomplish phased removal of infestations could enhance the quality of the remaining plants, thereby better integrating biological control into current E. crassipes management systems.

Tilletia barclayana: biologia e manejo em arroz irrigado

A cárie-do-arroz (Tilletia barclayana), doença considerada secundária na cultura do arroz irrigado, vem ganhando importância nos últimos anos devido aos níveis elevados de infestação e à redução do rendimento. A doença é favorecida por temperatura e umidade do ar elevadas, doses altas de nitrogênio e semeadura tardia. Para o manejo, recomenda-se uso de resistência varietal, semeadura na época recomendada e adubação equilibrada.

Estabelecimento do arroz irrigado e absorção de cátions em função do manejo da adubação potássica e do nível de salinidade no solo

O uso da água para a irrigação do arroz no Rio Grande do Sul, cujos mananciais hídricos têm ligação com o mar, pode ocasionar acúmulo de sais no solo em concentrações prejudiciais ao estabelecimento da cultura nos anos subsequentes, especialmente quando são aplicadas altas doses de fertilizante potássico na linha de semeadura. Este trabalho foi realizado com o objetivo de avaliar o efeito do manejo da adubação potássica sobre o estabelecimento e a absorção de cátions pelo arroz (cultivar IRGA 417) em um solo com diferentes níveis de saturação por Na. Foram utilizados um Planossolo Háplico com saturações por Na na troca de 5, 10 e 20 %; três manejos da adubação com cloreto de K equivalentes a 120 kg ha-1 de K2O a lanço; 120 kg ha-1 de K2O na linha de semeadura e 60 kg ha-1 de K2O na linha de semeadura, além de uma testemunha, sem adição de sal e de fertilizante, fatorial (3 x 3) + 1. O estande de plântulas não foi afetado pelos níveis de salinidade do solo e manejo da adubação potássica. A ontogenia da planta foi afetada pela salinidade, com atraso na emergência das plântulas. A salinidade do solo, a partir de 10 % de saturação por Na no complexo de troca, inibiu a absorção de K e reduziu o crescimento das plântulas de arroz, assim como diminuiu as relações K/Na, Ca/Na e Mg/Na no tecido. A interação entre manejo da adubação x salinidade reduziu o teor de Ca trocável no solo, aumentou o teor de Na na parte aérea e reduziu a relação Ca/Na na parte aérea do arroz.

Effect of precipitation and fertilization on the changes in soil organic carbon (SOC)

The present study aimed to determine the effect of precipitation and fertilization (NPKCaMg) on the changes in soil organic carbon (SOC) in a long-term field experiment set up in Nyirlugos (Nyirseg region, Hungary: N: 47° 41′ 60″ and E: 22° 2′ 80″) on a Haplic Luvisol with popular rotation crops. Over the 40 year period, from 1962 to 2002, SOC pool values ranged between 2.32 and 3.36 mg·kg−1. On the untreated control plots the values remained nearly constant (3.31 mg·kg−1: ±0.29 mg·kg−1 and 0.52 mg·kg−1). In the 1st 20-year period (1963–1982), there was a significant (P < 0.001) decrease (16%) on all experimental plots, which may be due to the winter half year (WHY) precipitation (228 mm), summer half year (SHY) precipitation (288 mm), the NPKCaMg fertilizer application rate (64 kg·ha−1), and the potato-rye-wheat-lupin-sunflower crop sequence. In the 2nd 20-year period (1983–2002) SOC pool values varied between 3.13 and 4.47 mg·kg−1. The 16.9% significant (P < 0.001) increase 16.9% could be attributed to the lower WHY (204 mm) precipitation, higher SHY (320 mm) precipitation, higher NPKCaMg fertilizer rate (213 kg·ha−1), and the sunflower-grass-barley-tobacco-wheat-triticale cropping system. NPKCaMg fertilization resulted in a significant (P < 0.001) decline (16.6%) in SOC in comparison to the control plots in the 1st 20-year interval, while in the 2nd 20-year period a significant (P < 0.001) rise (up to 31.9%) was registered. During the 40 experimental years the seasonal correlations (R2) among SOC (mg·kg−1), WHY and SHY precipitation (mm) ranged from 0.3343 to 0.9078 (on the P < 0.001 significance level). The correlations (R2) on the influence of NPKCaMg fertilization on SOC (mg·kg−1) and precipitation (mm) were significant (P < 0.001): the means for WHY, SHY and over the 40 years were 0.4691, 0.6171 and 0.6582, respectively. Organic carbon reserves (mg·kg−1) in soils decreased linearly as precipitation increased (from 3.22 to 7.27 mm·yr−1). In case this trend — increasing precipitation caused by climate change reduces SOC in arable soils — will continue, and is aggravated by warming temperatures and a more altering climate (as predicted by climate change forecasts), the livelihoods of many Hungarian and European farmers may be substantially altered. Thus, farmers must take into consideration the climate (WHY and SHY precipitation), fertilization (NPKCaMg), and cropping (tuber-seed-tobacco-protein-oil-forage) changeability to optimize their SOC pool, soil carbon sequestration, soil sustainability and crop management in the nearest future.

Comparative Forage Yield of “Poor” Versus “Good” Grass Stands under Different Soil Fertility Regimes in Northeastern Saskatchewan

ABSTRACT Forage yield and its response to fertilizers are affected by the condition of forage stands. A field experiment was conducted on a Gray Luvisol (Typic Croyoboralf) soil at Pathlow in northeastern Saskatchewan, from 2004 to 2006, to determine if low forage yields in “poor” grass stands are due to nutrient deficiencies, other soil properties and/or species composition, and to determine if forage dry matter yield (DMY), protein concentration (PC), and protein yield (PY) in these areas could be improved by fertilization. The four fertilizer treatments: no fertilizer—nil, plus three combinations of increasing amounts of nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) fertilizers (i.e., 45 kg N + 10 kg P + 12.5 kg K + 5 kg S ha−1; 90 kg N + 20 kg P + 25 kg K + 10 kg S ha−1; and 135 kg N + 30 kg P + 37.5 kg K + 15 kg S ha−1) were applied annually to the same plots in early spring of 2004 and 2005. The lower forage yield in “poor” compared to “good” grass stand areas was most likely due to differences in plant species composition, although other factors such as soil fertility and compaction may have also contributed to lower DMY. There was a significant response of DMY, PC, and PY to applied N, P, K, and S fertilizers in both “good” and “poor” grass stands in both years. The DMY, PC, and PY in the first year (2004) continued to increase up to the highest fertilizer rate used in this study, but in the second year (2005) there was no increase in total DMY in both grass stands, and in PC and PY in “good” grass stand with application of fertilizer blend beyond the 90 kg N + 20 kg P + 25 kg K + 10 kg S ha−1 rate. Fertilizer application for two years also increased the proportion of smooth bromegrass in both stands, indicating that proper nutrient management may increase the proportion of smooth bromegrass (high yielding grass species) in the “poor” growth area, thereby improving forage yields. Overall, the findings indicate that forage yields and quality in “poor” grass stand areas can be improved considerably by applying fertilizer nutrients that are lacking in the soil. Also, the significant responses observed in the “good” grass stand areas suggest that these regions of the field can also benefit from additional fertilization.

Growth and Nutrient Partitioning of Containerized Malus trilobata Schneid. and Acer syriacum Boiss. and Gaill. Under Two Fertigation Regimes

The native flora of Lebanon is threatened. As part of an ex situ conservation strategy, this study was conducted to determine if Malus trilobata (Schneid.) and Acer syriacum (Boiss. and Gaill.), two native Lebanese trees, were amenable to container production. Therefore, these species' growth and nitrogen, phosphorus, and potassium uptake efficiency and distribution under two fertilizer rates were studied. Malus trilobata seedlings were obtained from seeds collected from two mother trees, whereas Acer syriacum seeds were collected from a single tree. Two-year-old seedlings raised from these seeds were planted in 11-L containers in a 3:1 pine bark:compost substrate. Half the seedlings within each source and species were assigned to either 25 or 100 mg·L−1 N from 21N–3.1P–5.9K water-soluble fertilizer treatments. Seedlings of both Malus trilobata sources grown under 25 mg·L−1 N were taller than those grown at 100 mg·L−1 N. Nitrogen loading occurred in plants of Malus trilobata under the high fertilizer rate, although total plant N, phosphorus, and potassium content was unaffected by fertilizer rate, because larger seedlings had lower nutrient concentrations. There were significant differences in growth among the two Malus trilobata seed sources, but there were no differences in mineral nutrient uptake or nutrient use efficiency. Growth, mineral nutrient uptake, and nutrient use efficiency of Acer syriacum seedlings were unaffected by fertilizer rate. Malus trilobata and Acer syriacum seedlings are amenable to container production. Using container production for these species with subsequent transplanting into managed landscapes might be a viable ex situ conservation method. Further studies are needed.

Influence of Fertilization on the Colorado Potato Beetle, &lt;I&gt;Leptinotarsa decemlineata&lt;/I&gt;, in Organic Potato Production

The abundance of the Colorado potato beetle, Leptinotarsa decemlineata (Say), in organically grown potato did not change significantly in response to increasing rates of dehydrated poultry manure. However, peaks of abundance of larvae were shifted forward in time in response to the high rate of organic fertilizer. Tests using excised foliage showed that the shift was not caused by differential larval mortality or longer developmental times. Time allocation to resting, walking, and feeding by adults was similar regardless of fertilizer rate. Adult foliage consumption was unaffected by organic fertilizer rates in no choice tests and significantly affected in few choice tests. A 22% longer larval development time on plants treated with low fertilizer rate than on plants with high rate was the most significant effect. Even though maximum plant height, canopy, biomass, and yield were significantly smaller in the organic than in conventional plots, the suitability of the plants was not affected except for reduced feeding by summer beetles. Summer adults spent less time feeding and consumed two to five times less foliage on organic potato than on inorganically fertilized and conventionally produced plants. The overall influence of fertilizer on Colorado potato beetle populations was limited and therefore can only play a secondary role in management strategies for organic potato. Avoidance of excessive organic fertilizer that promotes short larval development time and extension of the period over which large Colorado potato beetle larvae are present should be recommended.

Effects of Mycorrhizal Colonization and Fertilization on Growth and Photosynthesis of Sweet Basil Under Salt Stress

ABSTRACT A greenhouse experiment was conducted to investigate the effects of inoculation with an arbuscular mycorrhizal fungus (AMF) and of different levels of fertilization on growth, photosynthetic efficiency, and ion uptake by sweet basil (Ocimum basilicum L.) in conditions of saline stress. Eight different treatments were compared, deriving from the factorial combination of two levels of fertilization, two levels of salinity of the irrigation water and the presence or absence of mycorrhizal colonization, performed with a crude inoculum of Glomus intraradices Schenck and Smith. Salinity significantly reduced growth and fluorescence level of plants, and higher sodium (Na) and chloride (Cl) contents in both roots and shoots were associated with these phenomena, while potassium (K) was slightly reduced. Both mycorrhizal inoculation and high fertilization acted in the direction of reducing the symptoms of salinity stress by increasing growth and fluorescence. Mycorrhizal colonization showed generally more pronounced effects than a high application rate of fertilizer. The simultaneous application of colonization and high fertilization provided higher tolerance to salinity than one single factor, but the combined effect was less than proportional to the sum of the separate effects. In particular, the differences in growth and photochemical efficiency between inoculated and uninoculated plants under salt stress were significantly reduced by the contemporary presence of additional fertilization. The rate of root colonization by the mycorrhizal fungus was significantly reduced by both saline irrigation and high fertilization.

Effects of Fertilizer Rate on Growth and Fruiting of Containerized Southern Highbush Blueberry

The effects of fertilizer rate and composition on growth and fruiting of ‘Misty’ and ‘Star’ southern highbush blueberry were evaluated in a containerized production system using pine bark medium. Two fertilizer analyses (12N–1.8P–46.6K and 12N–5.2P–9.9K) and three fertilizer rates were used. Plant growth and fruiting were unaffected by fertilizer analysis. Growth and fruit yield of ‘Star’ increased linearly with increasing fertilizer rate. For ‘Misty’, plant growth and yield were reduced at the highest fertilizer rate as a result of a high incidence of blueberry stem blight associated with that treatment. Flower bud density was highest for the ‘Misty’ plants receiving the high fertilizer rate and this may have resulted in excessive fruit set leading to stress-induced blueberry stem blight. Optimum fertilizer rates for young southern highbush blueberry plants grown in containerized pine bark systems appear to be cultivar-specific and similar to fertilizer requirements in soil culture.

Enhanced Efficiency Fertilizers for Improved Nutrient Management: Potato (Solanum tuberosum)

The improvement of fertilizer efficiency is driven by narrow profit margins, environmental concerns, and resource conservation. Fertile soil is the foundation for food production and successful civilizations; it is developed and maintained through the addition of nutrients lost through harvest. However, nutrient uptake by plants is inherently inefficient and the nutrients remaining in the soil after uptake can cause negative air and water resource impacts. In addition, poor fertilizer efficiency is a waste of natural resources and potentially reduces yields, crop quality, and grower profits. Enhancing fertilizer efficiency in potato is particularly important because relatively high rates of fertilizer and water are necessary to compensate for an inefficient rooting system and extreme sensitivity to deficiencies. Several new fertilizer materials have been designed to enhance fertilizer efficiency. The modes of action of these materials include: (i) slow or controlled release to meet plant need in a more timely fashion; (ii) addition of high charge-density materials that isolate nutrients from interfering elements and compounds; (iii) complexation or chelation of the nutrient to enhance solubility; and (iv) modification of the micro-site pH to enhance nutrient solubility.

Fertility Rate of Seacoast Marshelder Stock Plants Influences Cutting Production and Rooting Characteristics of Stem Cuttings

Seacoast marshelder (Iva imbricata) is an important coastal species contributing to building of foredunes along the Gulf of Mexico coastal regions. Hurricane activity disrupts natural regeneration, and the need for successful nursery production of sufficient plants for restoration warrants development of efficient propagation and production practices for restoration efforts. The objectives of these experiments were to investigate the effects of stock plant fertility on cutting production of seacoast marshelder and to evaluate the rooting qualities of cuttings harvested from hedged stock. Stock plants were established in 1-gal containers using a pine bark substrate amended with 6 lb/yard3 dolomitic limestone. Plants were fertilized with 15N–3.9P–10K controlled-release fertilizer (Osmocote Plus, 8- to 9-month formulation at 21 °C) applied as a top dressing at the recommended full label rate of 11 g per pot and 5.5, 15, and 21 g per pot (12 pots each) using a completely randomized design. Cuttings were collected and stock plants hedged on a regular interval [Expt. 1 (May to August) and Expt. 2 (August to November)]. Hedging of stock plants reduced height to 20 cm after each successive harvest of cuttings, but stock plant growth index increased with each successive harvest. Stock plant growth and cutting production increased as fertility rate increased, but responses were not consistent across harvest times. This trend was also true for rooting percentage and measures of root quality. Seacoast marshelder stock plant size increased as fertility increased to 15 g but not at 21 g. Inconsistencies in rooting responses across the production period were evident and were attributed to seasonal growth effects. An inverse relationship between rooting percentage and fertility rate was evident from May through July suggesting high levels of fertility should be avoided because rooting percentage, root number, and root length were reduced as fertility rate increased during that time. Conversely, higher fertilizer rates had a neutral to positive effect on rooting of seacoast marshelder during the months of August through November.