Comparison of hydroponic solutions for poinsettia nutritional studies 1

Poinsettia cultivars Supjibi and Freedom were grown in eight hydroponic solutions to develop a baseline solution for further nutritional studies. Four solutions contained nitrogen (N) from Ca(NO₃)₂‐4H₂O and KNO₃ (denoted as ‐NH₄) and four contained Ca(NO₃)₂‐4H₂O, KNO₃, nitric acid, and NH₄NO₃ as the N sources (denoted as +NH₄). The four ‐NH₄ and +NH₄ solutions were further divided by an IX or 2X rate of micronutrients [boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn)] (denoted as IX or 2X). A factorial of these four solutions at 2 concentrations (100 mg L¹ of N and potassium (K) and 15 mg L¹ phosphorus (P), or 300 mg L¹ of N and K and 46 mg L^‐1 P) was studied. Greater leaf and stem dry weight for both ‘Supjibi’ and ‘Freedom’ was observed in plants grown with the +NH₄ solutions, with a larger increase occurring with’ Supjibi’. Leaf NH₄‐N content for both cultivars was higher for both the 100 and 300 mg L^‐1 N and K fertilization rates when NH₄‐N was included. The leaf K content was highest for the plants grown with the +NH/2X solution for ‘Supjibi’, for both fertilization rates, and leaf K content increased as the K application rate increased. Results indicate that for nutritional studies with poinsettias, hydroponic solutions should include between 12.5% to 33% of the N in the NH₄ form, a calcium magnesium (Ca:Mg) ratio of 2:1, and a micronutrient concentration of (mg I/¹) 0.5, 0.02, 6.6, 0.5, 0.1, and 0.05, respectively, for B, Cu, Fe, Mn, Mo, and Zn, for adequate plant growth.     

Fertigation rate,leaching fraction,and growth of potted poinsettia

Single‐pinched poinsettia (Euphorbia pulcherrima ’V‐14 Glory') in 15‐cm pots received constant fertigation with 50, 100, 200, and 300 mg.L^‐1 nitrogen (N) from a 20N‐4.4 phosphorus (P)‐16.6 potassium (K) fertilizer with a leaching fraction (LF) of 0, 0.2, or 0.4. Plants received 25 irrigations during the 13‐week study. The shoot fresh and dry masses with 50, 100, and 300 mg.L^‐1 N at the 0.4 LF were 30% larger than at the 0 LF. The 300 mg.L^‐1 N fertigated plants had approximately 15% more leaf area and almost 122% more bract area than the 50 mg.L^‐1 N fertigated plants. The leaf N concentration of plants fertigated with 100, 200, and 300 mg.L^‐1 N was near or in the normal range of 4 to 6%, but was below the critical level of 3.5% with 50 mg.L^‐1 N fertigation. In contrast, the leaf P concentration approached or exceeded the toxic level of 0.9% with 100 to 300 mg.L^‐1 N. The N fertigation of 100 to 200 mg.L^‐1 is adequate for producing a quality poinsettia crop. Quality poinsettias can be grown at a 0 LF if quality irrigation water is available. With 11 mg.L^‐1 P via fertigation, the leaf P concentration was in the acceptable range. The P concentration in the 20N‐4.4P‐16.6K complete fertilizer was excessive for poinsettia and would contribute to unnecessary P leaching.     

DYNAMICS OF NITROGEN AND PHOSPHORUS PARTITION IN FOUR OLIVE TREE CULTIVARS DURING BUD DIFFERENTIATION

Variations of nitrogen and phosphorus levels in reproductive shoots and their leaves of self-rooting olive (Olea europaea) cultivars ‘Amfissis’ (A), ‘Kalamon’ (K), ‘Manzanillo’ (M), and ‘Chalkidikis’ (C) were monitored from the end of harvest until the emergence of the inflorescences. This 90-days period was divided into three sub-periods: before (pre-BD), during (BD), and after (post-BD) bud differentiation. The nitrogen (N)-content in leaves of the reproductive shoots varied between 10–20 mg g^?1 and among cultivars the order of decreasing concentration levels was C > K > A > M. The N-content in reproductive shoots varied between 6–14 mg g^?1 (K > A > C > M). Patterns of time-course variations are presented. Partitioning of N between leaves and shoots (N_L:N_S) varied with time, with a ratio between 1.5–2. The fluctuations in the N_L:N_S ratio over the 90 days showed two distinct phases: during pre-BD either increased (‘Amfissis’ and ‘Chalkidikis’) or remained relatively constant (‘Kalamon’ and ‘Manzanillo’), while during BD and post-BD decreased in all cultivars. The order of decreasing N_L:N_S ratio among cultivars was K > C > M > A.

Phosphorus (P) content in leaves of the reproductive shoots varied between 0.1–2.5 mg g^?1, (A > C > K > M). Phosphorus content in reproductive shoots varied between 0.2–1.6 mg g^?1, with the highest levels in ‘Amfissis’ compared to the other cultivars. Patterns of P partitioning between leaves and shoots were similar in all cultivars. The P_L:P_S ratio varied between 0.9–2 (A > C > K > M).

The N:P ratio varied between 5:1–20:1 in reproductive shoots and 10:1–35:1 in their leaves, increasing over the examined period. The increase rate of the N:P ratio varied between the three sub-periods, the lowest rate being during BD. The pattern of changes in the N:P ratio was similar in both leaves and shoots and an increase of N:P ratio in leaves was highly correlated with the corresponding increase of N:P in shoots.     

Optimum plant stand and nutrient doses for summer groundnut under check basin irrigation and drip fertigation in light black soils of peninsular Western India

Abstract

A field experiment was conducted at Research Farm of ICAR-Directorate of Groundnut Research, Junagadh for consecutive three summer seasons of 2013, 2014, and 2015 with the objectives of identifying optimum plant density and nutrient doses under check basin irrigation and drip fertigation for higher productivity and net returns. The treatments were; three plant densities viz., 3,33,333 plants/ha (100% of recommended plant density; P1); 4,16,666 plants/ha (125% of recommended plant density; P2), and 4,99,999 plants/ha (150% of recommended plant density;P3) in main plots, and three nutrient doses viz., 18.75–37.5–22.5 NPK kg ha^?1 (75% of recommended nutrient dose; F1), 25-50-30 NPK kg ha^?1 (100% of recommended nutrient dose; F2), and 31.25–62.5–37.5 NPK kg ha^?1 (125% of recommended nutrient dose; F3) in sub-plots, and replicated thrice. The same sets of treatments were tested under both check basin irrigation and drip fertigation. The data were analyzed using split plot design. Pod yield, haulm yield, and net returns were significantly higher with P3 as compared to P1 under check basin irrigation but only haulm yield was found significantly higher with P3 under drip fertigation. Under check basin irrigation, NH₄–N, NO₃–N, and available P and K in soil were found in the order P1?>?P2?>?P3 (p?<?0.05) while in case of drip fertigation, differences were significant only for available K which was significantly higher in P1 over both P2 and P3. Under check basin irrigation, F2 i.e., application of 100 percent of recommended nutrient doses, being at par with F3, significantly improved pod yield, haulm yield and net returns over that with F1 however, differences were not significant under drip fertigation. NH₄–N, NO₃–N and available P and K in soil under both the irrigation systems were in the order F3?>?F2?>?F1 (p?<?0.05).     

Growth and chloroplast ultrastructure of two citrus rootstock seedlings in response to ammonium and nitrate nutrition 1

Abstract

It is important to understand the differential response of citrus rootstock to various rates of nitrogen (N) forms in order to evaluate the tree response to N availability under different production conditions. In this study, the effects of N sources (NH₄‐N or NO₃‐N), and rates (5, 15, 45, and 135 mg N L^?1) on two citrus rootstock seedlings (Swingle citrumelo, SC; Cleopatra mandarin, CM) growth (110 d) and N concentrations in various parts of seedling were investigated in a nutrient solution experiment. The effects of N nutrition on the chloroplast ultrastructure of leaves were examined at the end of the experiment. Rootstock and N sources significantly influenced the growth of leaves, stems, and roots. The growth of all seedling parts of both rootstocks decreased with an increase in concentration of NH₄‐N in the solution. In contrast, there was a positive relationship between the seedling growth and the concentration of NO₃‐N in the nutrient solution with marked response observed as the NO₃‐N concentration increased from 5 to 15 mg L^?1 The experiment demonstrated a distinct growth suppression effect with an increase in concentration of NH₄‐N in the nutrient solution, particularly SC rootstock. Chloroplast ultra‐structure of the leaves showed evidence of injury of the seedlings which received N entirely as NH₄ ⁺ form, but the injury was not seen when the seedlings received N as the NO₃‐N form. The disruption of chloroplast ultrastructure increased with increased rate of NH₄‐N. The most conspicuous characteristic of ammonium toxicity was the massive accumulation of strands granules and phytoferritin which is clearly an evidence of NH₃ toxicity. The results are important for understanding the implications of N source on seedling growth and chloroplast structure of citrus leaves.     

Distribution of phosphorus in size fractions of sandy soils with different fertilization histories

A major challenge in sustainable crop management is to ensure adequate P supply for crops, while minimizing losses of P that could negatively impact water quality. The objective of the present study was to investigate the effects of long‐term applications of different levels of mineral fertilizers and farmyard manure on (1) the availability of P, (2) the relationship between soil C, N, and P, and (3) the distribution of inorganic and organic P in size fractions obtained by wet sieving. Soil samples were taken from the top 20 cm of a long‐term (29 y) fertilization trial on a sandy Cambisol near Darmstadt, SW Germany. Plant‐available P, determined with the CAL method, was little affected by fertilization treatment (p < 0.05) and was low to optimal. The concentration of inorganic and organic P extracted with a NaOH‐EDTA solution (P_NaOH‐EDTA) averaged about 350 mg (kg dry soil)^–1, with 42% being in the organic form (P_o). Manure application tended to increase soil C, N, and P_o concentrations by 8%, 9%, and 5.6%, respectively. Across all treatments, the C : N : P_o ratio was 100 : 9.5 : 2 and was not significantly affected by the fertilization treatments. Aggregate formation was weak due to the low clay and organic‐matter content of the soil, and the fractions > 53 μm consisted predominantly of sand grains. The different fertilization treatments had little effect on the distribution of size fractions and their C, N, and P contents. In the fractions > 53 μm, P_NaOH‐EDTA ranged between 200 and 300 mg kg^–1, while it reached 1260 mg kg^–1 in the fraction < 53 μm. Less than one third of P_NaOH‐EDTA was present as P_o in the fractions > 53 μm, while P_o accounted for 70% of P_NaOH‐EDTA in the smallest fraction (< 53 μm). Therefore, 16% and 28% of P_NaOH‐EDTA and P_o, respectively, were associated with the smallest fraction, even though this fraction accounted for < 5% of the soil mass. Therefore, runoff may cause higher P losses than the soil P content suggests in this sandy soil with a weak aggregate formation. Overall, the results indicate that manure and mineral fertilizer had similar effects on soil P fractions.     

Fate of phosphorus in soil during a long‐term fertilization experiment in Finland

Accumulation and depletion of soil phosphorus (P) was studied in a long‐term (37 y) field experiment in Southern Finland. The loam soil had a high pH (7.5–7.7) due to an earlier liming. Spring barley, spring wheat, oat, and ryegrass, grown in rotation, were annually fertilized with 0, 32, or 67 kg P ha^?1 y^?1 (P₀, P₁, and P₂K) and sufficient N. The average dry matter grain yield 2,600 kg ha^?1 of the P₀ plots increased by about 500 kg ha^?1 at P₁ treatment and another 600 kg ha^?1 by P₂K. Soil samples were collected in 1978 (beginning), 1995, 2005, and 2015. According to the Chang and Jackson sequential extraction, the P₂K and P₁ treatments increased the inorganic soil P by 732 and 32 kg P ha ^?1 in 37 years, respectively, while the P₀ plots were depleted by –459 kg P ha ^?1. The P₂K treatment increased all four P fractions, extracted with NH₄Cl (easily soluble), NH₄F (Al‐P), NaOH (Fe‐P), and H₂SO₄ (Ca‐P). Continuous depletion (P₀) decreased the NH₄Cl‐P and NH₄F‐P pools, NaOH‐P and H₂SO₄‐P pools remaining stable. None of the P pools changed significantly at P₁. The remarkable gap between the measured change and the balance for the P₂K and P₁ treatments cannot be explained solely by lateral soil movement, meaning that a significant proportion of the applied P was lost either in surface runoff or transported below the investigated depth of 40 cm. Despite large P applications, the degree of P saturation reached only 20% in the P₂K topsoil, assuming a 50% reactivity of Fe and Al oxides. As derived from sorption isotherms, a high EPC₀ (i.e., equilibrium P concentration at zero net P sorption or desorption) of 1.30 mg L^?1 had been built up in the P₂K treatment, while in the P₁ treatment EPC₀ (0.33 mg L^?1) had remained unchanged and P depletion (P₀) had caused a decrease to 0.12 mg L^?1. These results demonstrate that P sorption and desorption properties respond strongly to both P fertilization and null fertilization treatments and that in a long‐term field experiment only a low proportion of the residual fertilizer P can be recovered from soil.     

Gaseous emissions of nitrogen and carbon from urban vegetable gardens in Bobo‐Dioulasso,Burkina Faso

Urban and peri‐urban agriculture (UPA) is an important livelihood strategy for the urban poor in sub‐Saharan Africa and contributes to meeting increasing food demands in the rapidly growing cities. Although in recent years many research activities have been geared towards enhancing the productivity of this land‐use system, little is known about turnover processes and nutrient efficiency of UPA. The aim of our study therefore was to determine horizontal fluxes of N, P, K, and C as well as gaseous N and C emissions in urban vegetable gardens of Bobo‐Dioulasso, Burkina Faso. Two gardens referred to as “Kodéni” and “Kuinima” were selected as representative for urban and peri‐urban systems classified as: (1) “commercial gardening + field crops and livestock system” and (2) “commercial gardening and semicommercial field crop system”, respectively. A nutrient‐balance approach was used to monitor matter fluxes from March 2008 to March 2009 in both gardens. Ammonia (NH₃), nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions from the respective soils were measured during the coolest and the hottest period of the day using a closed‐chamber system. Annual partial balances amounted to 2056 kg N ha^–1, 615 kg P ha^–1, 1864 kg K ha^–1, and 33 893 kg C ha^–1 at Kodéni and to 1752 kg N ha^–1, 446 kg P ha^–1, 1643 kg K ha^–1, and 21 021 kg C ha^–1 at Kuinima. Emission rates were highest during the hot midday hours with peaks after fertilizer applications when fluxes of up to 1140 g NH₃‐N ha^–1 h^–1, 154 g N₂O‐N ha^–1 h^–1, 12 993 g CO₂‐C ha^–1 h^–1 were recorded for Kodéni and Kuinima. Estimated annual gaseous N (NH₃‐N + N₂O‐N) and C (CO₂‐C + CH₄‐C) losses reached 419 kg N ha^–1 and 35 862 kg C ha^–1 at Kodéni and 347 kg N ha^–1 and 22 364 kg C ha^–1 at Kuinima. For both gardens, this represented 20% and 106% of the N and C surpluses, respectively. Emissions of NH₃, largely emitted after surface application of manure and mineral fertilizers, accounted for 73% and 77% of total estimated N losses for Kodéni and Kuinima. To mitigate N losses nutrient‐management practices in UPA vegetable production of Bobo‐Dioulasso would greatly benefit from better synchronizing nutrient‐input rates with crop demands.     

Controlled‐release urea decreased ammonia volatilization and increased nitrogen use efficiency of cotton

Excessive nitrogen (N) fertilizer input leads to higher N loss via ammonia (NH₃) volatilization. Controlled‐release urea (CRU) was expected to reduce emission losses of N. An incubation and a plant growth experiment with Gossypium hirsutum L. were conducted with urea and CRU (a fertilizer mixture of polymer‐coating sulfur‐coated urea and polymer‐coated urea with N ratios of 5 : 5) under six levels of N fertilization rates, which were 0% (0 mg N kg⁻¹ soil), 50% (110 mg N kg⁻¹ soil), 75% (165 mg N kg⁻¹ soil), 100% (220 mg N kg⁻¹ soil), 125% (275 mg N kg⁻¹ soil), and 150% (330 mg N kg⁻¹ soil) of the recommended N fertilizer rate. For each type of N fertilizer, the NH₃ volatilization, cotton yield, and N uptake increased with the rate of N application, while N use efficiency reached a threshold and decreased when N application rates of urea and CRU exceeded 238.7 and 209.3 mg N kg⁻¹ soil, respectively. Ammonia volatilization was reduced by 65–105% with CRU in comparison to urea treatments. The N release characteristic of CRU corresponded well to the N requirements of cotton growth. Soil inorganic N contents, leaf SPAD values, and net photosynthetic rates were increased by CRU application, particularly from the full bloom stage to the initial boll‐opening stage. As a result, CRU treatments achieved significantly higher lint yield by 7–30%, and the N use efficiency of CRU treatments was increased by 25–124% relative to that of urea treatments. These results suggest that the application of CRU could be widely used for cotton production with higher N use efficiency and lower NH₃ volatilization.     

Evaluating Bearberry Nitrogen Nutrition Using Hydroponic Cultures: Establishing Preliminary DRIS Norms

Abstract

This study was designed to explore nitrogen (N) nutrition in bearberry plants (Arctostaphylos uva‐ursi L.) using a hydroponic culture system. Two experiments were performed in which the total N concentration (34, 52, and 73 mg L^?1) and N‐NO₃ ^?:N‐NH₄ ⁺ ratio (50/50, 60/40, and 70/30 in %) in the nutrient solution were varied and effects on nutrient uptake [N, phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] and foliar composition determined. Highest‐quality plants were yielded using a N level of 73 mg L^?1 and a N‐NO₃ ^?:N‐NH₄ ⁺ ratio of 50/50. Standard nutrient values for foliar tissue were obtained for bearberry plants growing in these hydroponic cultures for their use as preliminary norms in the diagnosis and recommendation integrated system (DRIS). In a subsequent complementary experiment, these norms were used in the DRIS procedure and applied to plants growing in solutions of varying K concentrations. It was found that the DRIS norms established in the hydroponic experiments were able to account for changes in nutrient limiting factors produced in response to the varying K concentrations in the nutrient solution. The results obtained will be useful for the nutritional diagnosis of bearberry plants.     

Study of conifer nitrogen nutrition using hydroponic cultures: Application to fertigation systems

Nitrogen (N) optimization of a nutrient solution for ornamental conifers was obtained with two different experiments in hydroponic cultures: First, by using three different NO₃ ^‐/NH₄ ⁺ ratios (60/40, 55/45, and 40/60 in percentages of the total N supplied); and, secondly by testing three total N levels (3.7; 4.7 and 5.5 mmol L^‐1). Best growth was obtained with a NO₃ ^‐/NH₄ ⁺ ratio of 55/ 45 and a total N level of 3.7 mmol L^‐1. With these experiments, reference levels of foliar concentrations of the macronutrients N, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and the biochemical indices, such as chlorophyll and starch levels, were obtained with the treatments corresponding to the plants with the higher growth. In the course of a growth cycle, a substrate assay with two different pot mixes (moss peat plus perlite and black peat plus sepiolite 60/40 ‐% v/v‐) was carried out by using the best N ratios and doses in nutrient solutions as obtained in hydroponics. The results indicated that the same N fertilization in fertigation systems changes depending on the different physicochemical properties of the substrates used; in this case, depending on the different physical properties of the two substrates. By applying DRIS to perform nutritional diagnosis, it is possible to find nutritional limitations to plant growth, but not additional factors, such as water‐air relationships in the growth media.     

PANSY FLORAL DEVELOPMENT AND NUTRIENT ABSORPTION AS INFLUENCED BY TEMPERATURE,NITROGEN FORM,AND STAGE OF PLANT DEVELOPMENT

Production temperatures can affect the marketability of pansies (Viola × wittrockiana Gams.) by influencing plant growth, the presence of nutrient disorders, and the rate of floral development. The choice of nitrogen (N) form in fertility can also influence pansy growth and nutrition, but the effect of fertility on pansy flowering is not clear. Whether or not temperature and N fertility work together to influence nutrient absorption at different stages of the pansy life cycle is unknown. Our objectives were to determine the influence of temperature and N form on pansy floral development, and to identify the peak nutrient demand periods at different temperatures and ratios of NO₃ ^? to NH₄ ⁺ in fertility. Pansies cv. ‘Crown White’ were grown in nutrient solution cultures until lateral branches had open flowers. Treatments consisted of two temperatures (12°C and 22°C) and three stages of floral development (five true leaf stage until visible bud, visible bud until first flower, first flower until flowering on lateral branches), and three NO₃ ^? :NH₄ ⁺ molar % ratios (100:0, 62:38, 25:75) with a total concentration of 100 mg N L^?1. A modified Hoagland's solution was used with NO₃ ^??N supplied as Ca(NO₃)₂ and KNO₃ and with NH₄ ⁺?N as (NH₄)₂SO₄. The effects of temperature and N form on the time required for development of different floral stages were assessed. In addition, the influence temperature and N form on nutrient absorption was determined for three pre‐determined stages of floral development to identify peak nutrient demand periods. The timing of flower bud development and first flower was not influenced by treatments. At 22°C, pansies flowered earlier on lateral branches than at 12°C, but these plants also suffered a loss in quality due to unfavorable growth characteristics and the development of nutritional disorders. Individual absorption of plant nutrients at different stages of development varied with temperature and N regime. Overall, pansies absorbed the greatest quantity of magnesium (Mg) before flower bud development, calcium (Ca) after flower bud development, and NH₄ ⁺, NO₃ ^? phosphorus (P), and potassium (K) after anthesis. In addition, pansies absorbed more NO₃ ^?, Ca, Mg, and P at 12°C than at 22°C. At times, the absorption of NO₃ ^? was dramatically decreased with increasing NH₄ ⁺ in solutions. Results suggest that nutrient absorption by pansy in different stages of development is influenced by production temperatures and the choice of N form in fertilization. Adjusting fertility programs according to peak demand periods and production temperatures will help prevent periodic nutrient disorders during the life cycle, and may reduce fertilization costs.     

Nitrogen and phosphorus fertilizations alter nitrogen,phosphorus and potassium resorption of alfalfa in the Loess Plateau of China

Abstract

Nutrient resorption from senescing leaves is a pivotal component of nutrient conservation strategy in a plant. Thus understanding the response of nutrient resorption to fertilization is of great help to minimize fertilizer use and further optimize fertilization management. However, little is known about how nutrient resorption responds to fertilization in N₂-fixing species. Nitrogen (N) and phosphorus (P) fertilizers were applied at different rates to alfalfa stands in the Loess Plateau. N fertilization hardly affected leaf N and K resorptions, but tended to increase P resorption. P fertilization increased N and K resorptions but affected P resorption in various ways. However, effect of N or P fertilization was significantly interplayed by P or N rate. At N100P60, alfalfa had the maximum biomass accumulation and less leaf resorption. Therefore, alfalfa could be performed well with 100?kg N ha^?1 and 60?kg P₂O₅ ha^?1 in this region.     

Current potassium‐management status and grain‐yield response of Chinese maize to potassium application

The great achievement of the development of intensive in agriculture in China can be partly attributed to substantial increases in mineral‐nutrient application. However, whereas farmers tend to apply high levels of nitrogen (N) and phosphorus (P) application of potassium (K) has been neglected. A greater understanding of the relationship between maize (Zea mays L.) grain yield and K‐application rate is thus required to provide an improved rationale for K fertilization for farmers in the various agro‐ecological regions of China. In this study, a total of 2765 farmers' survey data and 3124 on‐farm experiments across major maize agro‐ecological regions in China were collected and evaluated for farmers' K‐management status and to determine grain‐yield response to K application. Nationally, the average K‐application rate on farms was 26 kg K ha^–1 and varied from 0 to 158 kg K ha^–1, with a coefficient of variation of 107%, but the applied K‐fertilizer rates were not related to grain yield. Maize grain yields at recommended K rates increased by 14.0%, 14.7%, 19.4%, and 4.3% in Northeast China, North China Plain, Southwest China, and Northwest China, respectively, compared to zero K fertilization (K₀). Increased yield due to K fertilization (IY_max, difference between maximum yield across all treatments and K₀‐treatment yield for each experiment) averaged 1.4 t ha^–1 but varied widely in different agro‐ecological regions. Soil extractable K (NH₄OAc‐K) and intercounty variation resulted in large variation in IY_max in agro‐ecological regions, as did other factors, such as use of particular maize hybrids, soil types, or years in different regions.     

Microsite assessment of forest soil nitrogen,phosphorus, and potassium supply rates in‐field using ion exchange membranes

Abstract

A new method for microsite assessment of soil nutrient supply in forest soil was developed. The method involves the use of ion exchange membranes to assess differences in soil nitrogen (N), phosphorus (P), and potassium (K) supply rates in‐field over small depth increments in the forest floor (i.e., the L, F, and H horizons). Ion exchange membranes were buried and retrieved from the forest floor in an aspen forest stand in Saskatchewan, Canada. Small (6 mm diameter) sections of the membrane were cut out and ion concentration on the sections measured to provide a nutrient supply rate at that location. Soil nutrient supply rates at the site ranged from 4.6–6.0, 7.3–8.5, 11.6–21.5, and 122–196μg 10 cm²#lb2 h^‐1 for NH₄ ⁺‐N, NC₃ ^‐‐N, P, and K, respectively. On average, the highly humified H horizon had the highest N and P supply rates, followed by the F horizon, with the surface litter (L horizon) having the lowest N supply rates. The simplicity and sensitivity of the procedure make this method appropriate for in‐field assessment of differences in soil nutrient supply over small vertical and horizontal distance and was especially appropriate for the forest floor horizons in forest soils.     

Assessment of Ionic Interferences to Nitrate and Potassium Analyses with Ion-Selective Electrodes

Ion-selective electrodes (ISEs) are simple tools used for rapid measurement of nitrate nitrogen (NO₃-N) and potassium (K) concentrations in plant sap. With the development of best management practices (BMPs), interest exists in using ISEs for soil leachate and soil and fertilizer solutions. Nitrate N and K concentrations in the 0 to 10,000 mg L^–1 ISE working range were measured in diluted solutions of common salts to assess ionic interference of calcium (Ca²⁺), ammonium (NH₄ ⁺), chloride (Cl^–), and sulfate (SO₄ ^2–). The effects of meter (replication) were unexpectedly significant in one out of three ranges for NO₃-N and K (P values of 0.50, 0.72, and 0.01 for NO₃-N and 0.99, 0.01, and 0.74 for K, for the 0–100, 100–1,000 and 1,000–10,000 mg L^–1 ranges, respectively). The responses of calculated NO₃-N and K concentrations to measured NO₃-N and K concentrations were linear, but slopes ranged from 0.85 to 1.54, from 0.24 to 2.72, and from 0.93 to 5.48 for NO₃-N and from 0.80 to 1.01, from 0.71 to 1.39, and from 0.93 to 2.21 for K for the 0–100, 100–1,000, and 1,000–10,000 mg L^–1 measuring ranges, respectively. All slopes were significantly different from zero, and several were significantly different from each other and the 1:1 line. Pairwise slope comparisons conducted with covariance analysis showed that SO₄ ^2– alone interfered with NO₃-N measurements at concentrations ranging from 34 to 171 mg L^–1, which was less than the manufacturer's information, and by its presence in combination with K⁺, NH₄ ⁺, Ca²⁺, and Cl^– within the medium and high concentration ranges. Potassium measurements were not subject to interference from the ions tested for all three concentration ranges. These results highlight the importance of using quality assurance / quality control (QA/QC) samples in the set of unknown samples to detect inacceptable departure from linearity in routine analysis. The increase in measurement variability from one range to the next showed the importance of keeping measurements within a single concentration range by using dilutions. Hence, ISEs may be used for field measurements of NO₃-N and K concentrations in soil leachate as well as soil and nutrient solutions and are therefore a practical BMP tool. However, ISEs should not be used as substitutes for the laboratory methods when official measurements are needed.     

Assessing long term effects of compost fertilization on soil fertility and nitrogen mineralization rate

Background

Fertilization with organic waste compost can close the nutrient cycles between urban and rural environments. However, its effect on yield and soil fertility must be investigated.

Aim

This study investigated the long-term effect of compost on soil nutrient and potentially toxic elements (PTEs) concentration, nutrient budgets, and nitrogen (N) mineralization and efficiency.

Methods

After 21 years of annual compost application (100/400 kg N ha^–1 year^–1 [100BC/400BC]) alone and combined with mineral fertilization, soil was analyzed for pH, organic carbon (SOC), nutrient (total N and P, N_min, extractable CAL-P, CAL-K, and Mg), and PTE (Cu, Ni, Zn) concentrations. Yields were recorded and nutrient/PTE budgets and apparent net mineralization (ANM, only 2019) were calculated.

Results

N efficiency was the highest in maize and for mineral fertilization. Compost application led to lower N efficiencies, but increased ANM, SOC, pH, and soil N, and surpluses of N, P, and all PTEs. Higher PTE concentrations were only found in 400BC for Cu. Nutrient budgets correlated with soil nutrient concentration. A surplus of 16.1 kg P ha^–1 year^–1 and 19.5 kg K ha^–1 year^–1 resulted in 1 mg kg^–1 increase in CAL-P and CAL-K over 21 years.

Conclusion

Compost application supplies nutrients to crops with a minor risk of soil-accumulation of PTEs. However, the nutrient stoichiometry provided by compost does not match crop offtakes causing imbalances. Synchronization of compost N mineralization and plant N demand does not match and limits the yield effect. In winter wheat only 65–70% of N mineralization occurred during the growth period.     

Poinsettia growth,tissue nutrient concentration,and nutrient uptake as influenced by nitrogen form and stage of growth

Growth, development, and uptake of essential nutrients as influenced by nitrogen (N) form and growth stage was evaluated for ‘Freedom’ poinsettias (Euphorbia pulcherrima Willd. Ex Klotz.). Treatments consisted of five nitrate (NH₄ ⁺):ammonium (NO₃ ^‐) ratios (% NH₄ ⁺:% NO₃ ^‐) of 100:0, 75:25, 50:50, 25:75, and 0:100 with a total N concentration of 150 mg L^‐1. Plants were grown in solution culture for ten weeks under greenhouse conditions. Nutrient uptake data was combined into three physiological growth stages. Growth stage I (GSI) included early vegetative growth (long days). Growth stage II (GSII) began at floral induction and leaf and bract expansion (short days). Growth stage III (GSIII) was from visible bud through anthesis and harvest. Dry weights for all plant parts and height increased as the ratio of NO₃ ^‐ increased. Leaf area and bract area were maximized with 25:75 and 50:50 N treatments, respectively. Nitrogen treatments significantly affected foliar nutrient concentrations with calcium (Ca⁺⁺) and magnesium (Mg⁺⁺) being highest when NO₃ ^‐ was the predominant N form. Uptake of each macronutrient was averaged across all treatments and divided into physiological growth stages (GS) to identify peak demand periods during the growth cycle. The greatest uptake of NH₄ ⁺ and NO₃ ^‐ was from the early vegetative stage to floral induction (GSI). Phosphorus (P), potassium (K⁺), and Mg⁺⁺ uptake were greatest from floral induction to visible bud (GSII) and Ca⁺⁺ uptake remained relatively unchanged through GSI and GSII. Uptake was lowest for all nutrients from visible bud to anthesis (GSIII). Results from this study clearly indicate that peak demand periods for macronutrient uptake existed during the growth cycle of poinsettia.     

Effect of Potassium Supplies on the Nutritional Status of Maize (Zea mays L.)

The effect of soil potassium (K) supplies on the yield and nutritional status of maize and on interactions between the nutrients was examined in a long-term mineral fertilization experiment on maize. The experiment was set up in 1989 in Hungarian Great Plain, Szarvas on chernozem meadow soil calcareous in the deeper layers, with four levels each of nitrogen (N), phosphorus (P) and potassium (K) supplies. The present paper describes the results of K fertilization in the 7–19th years of the experiment, from 1996 to 2008. The ammonium (NH₄)-lactate (AL) potassium oxide (K₂O) content of the ploughed layer ranged from 200 to 550 mg kg^–1 depending on the K fertilization level. No significant yield surpluses were recorded in any of the 13 years in response to the better K supplies ensured by K fertilizer. The results of leaf analysis indicated that the K concentrations representing satisfactory K supplies at a grain yield level of 10–14 t ha^–1 were 2.3–4.3% at the 5–6-leaf stage and 1.5–2.6% at the beginning of tasselling. When the AL-K₂O content of the soil was above 200–320 mg kg^–1, K– calcium (Ca), K–magnesium (Mg) and K–copper (Cu) antagonism was observed in the nutrient concentrations of the maize leaves in most years. The limit values of satisfactory nutrient supplies for maize in the 5–6-leaf stage and at the beginning of tasselling were 0.25–0.60% for Ca, 0.15–0.40% for Mg, and 7–11 mg kg^–1 and 2–11 mg kg^–1, respectively, for Cu. In dry years the iron (Fe) and zinc (Zn) concentrations of maize leaves declined at higher soil K supply levels.     

Nutrient flows and balances in intensively managed vegetable production of two West African cities

This study reports and analyzes nutrient balances in experimental vegetable production systems of the two West African cities of Tamale (Ghana) and Ouagadougou (Burkina Faso) over a two‐year period comprising thirteen and eleven crops, respectively. Nutrient‐use efficiency was also calculated. In Tamale and Ouagadougou, up to 2% (8 and 80 kg N ha^?1) of annually applied fertilizer nitrogen were leached. While biochar application or wastewater irrigation on fertilized plots did not influence N leaching in both cities, P and K leaching, as determined with ion‐absorbing resin cartridges, were reduced on biochar‐amended plots in Tamale. Annual nutrient balances amounted to +362 kg N ha^?1, +217 kg P ha^?1, and –125 kg K ha^?1 in Tamale, while Ouagadougou had balances of up to +692 kg N ha^?1, +166 kg P ha^?1, and –175 kg K ha^?1 y^?1. Under farmers' practice of fertilization, agronomic nutrient‐use efficiencies were generally higher in Tamale than in Ouagadougou, but declined in both cities during the last season. This was the result of the higher nutrient inputs in Ouagadougou compared to Tamale and relatively lower outputs. The high N and P surpluses and K deficits call for adjustments in local fertilization practices to enhance nutrient‐use efficiency and prevent risks of eutrophication.