Nitrate Meter Research Articles

Impact of transportation on the environmental friendliness of agricultural food products

This article examines the impact of transportation on the sustainability of agricultural food products. To identify the impact of the transportation process on food quality, this study analyzed the content of harmful substances (nitrates) in several batches of potato fruits before and after the transportation process from the place of harvest to the place of storage. The measurements were carried out using an ecotester – a nitrate meter. The measurement was carried out in three batches of potato fruits collected from different agricultural fields. The results obtained allow us to assess the level of influence of transportation on the environmental friendliness of potato fruits. The results of the study are relevant for further research in the field of improving the quality and environmental friendliness of food products, including through optimization of their transportation processes, and can also be used in conducting broader research in the field of agriculture and ecology.

Clinical and toxicological findings in nitrate and nitrite poisoning in cattle in Northeastern Brazil

ABSTRACT: We report two outbreaks of nitrate and nitrite poisoning in Paraíba, Northeast Brazil. The first, due to Pennisetum purpureum (elephant grass), and the second, due to P. purpureum and Brachiaria spp. (brachiaria grass), both occurred during a prolonged drought. In the first outbreak, the irrigation of the pastures with wastewater and sewage contributed to nitrate accumulation. The second outbreak occurred in pastures cultivated in the border of a dam, that had been submerged for long time accumulating large amounts of organic matter in the soil. Other probably risk factors for nitrate accumulation included the use of chemical fertilizers and herbicides and burning of the vegetation. In the first outbreak, four calves out of a total of 42 cattle died, and in the second outbreak 49 out of 243 cattle, including adults, yearlings, and a 2-day-old calf died. The clinical signs included dyspnea, cyanosis, ataxia, and falls, leading to death. The presence of nitrates was detected in both outbreaks using the diphenylamine test. Quantitative tests were performed in the second outbreak using a portable nitrate meter, and high nitrate concentrations were found. The characteristic macroscopic findings and absence of microscopic lesions and response to treatment with methylene blue were key to the diagnosis of poisoning by nitrates and nitrites. We conclude that poisoning by nitrates and nitrites in ruminants in the semiarid region of Northeastern Brazil is frequent due to the cultivation of grasses in the border of dams that had been covered by water for long periods or in areas irrigated by wastewater and/or sewage. In addition, the use of a portable measuring device is an effective alternative for the quantification of nitrates in pastures.

Diet Composition and Seasonal Fluctuations in the Feeding Habit of Snow Barbel (Schizothorax plagiostomus) in River Indus, Pakistan

Background:Schizothorax plagiostomus is widely distributed in river Indus and is most important food fish in Pakistan. The feeding habit of fish is directly related to the size of fish, its metabolic rate and environmental temperature. The accurate description of fish diet and feeding habit is a very important aspect in fisheries management for the purpose of species conservation, breeding and culture. The present work was aimed to investigate the specie abundance, the diet composition and seasonal variations in the feeding habit of Snow barbell Schizothorax plagiostomus.Materials, Methods & Results: A total of 1799 fish specimens were caught at the confluence of six tributaries along river Indus at Indus Kohistan, northeastern Pakistan. The fish were collected by 5-panels of gill net during first week of each month. The site specific Catch Per Unit Effort (CPUE) and season specific CPUE of fish fauna were assessed. For the gut content analysis 240 samples (99 male and 141 females) of S. plagiostomus were selected on monthly basis. Frequency of occurrence method and volumetric method were applied to record the different food items in the gut of S. plagiostomus. The physico-chemical parameters, NO3 concentration and dissolved Co2 of water from different localities of river Indus were recorded month wise by Hach sensION 156 meter, Horiba LAQUA Nitrate Meter and EA80 meter respectively. Significant difference was observed in water temperature during the four seasons. Except alkalinity no other water parameter showed significant variation across different localities. The results showed that highest Mean CPUE was observed for Darel Stream (0.55) and lowest for Jalkot stream (0.26). Peak abundance of fish was recorded in the month of November with a mean catch of 44.50, mean CPUE of 0.74 and mean Kruskal-Wallis rank value of 63.25. Spirogyra and Ulothrix occurred as maximum food items in the gut of S. plagiostomus during summer while their minimum amount occurred during autumn. According to the ranking index spirogyra and ulothrix ranked higher with significant difference in comparison to other food items. The results showed that S. plagiostomus is phytophagous in its feeding habit, which consumed mainly algae attached to stones and pebbles during the whole year. However, the presence of some secondary items such as animal matter, detritus, sand and mud might be due to the distinct availabilities of food along the seasons. The highest feeding activity of S. plagiostomus was recorded during summer while the lowest one occurred during autumn, spring and winter. Discussion: Catch per unit effort (CPUE) is an indirect measure of the abundance of a target species. It is used as an index of stock abundance in fisheries and conservation biology. During the study low fish fauna was found in River Indus as reported previously. Majority of the fish occurred in snow fed river tributaries in the study area as these tributaries are comparatively less turbulent. Previous studies have also recorded that Schizothoracine generally prefer clean waters. The present findings of gut contents analysis showed clearly that S. plagiostomus is a phytophagous fish which scrap and consumed spirogyra and ulothrix attached to stones and pebbles. Earlier it was reported that mouth of S. plagiostomusis is inferior, wide, with deep lower jaw having keratinized cutting edge and the lower lip is folded and expanded with numerous papillae making it best suited for scrapping algae attached to stones and pebbles. The highest feeding activity was observed during warmer months as compared to cold months. S. plagiostomus spawn twice in a year in autumn and in spring. The highest feeding activity of S. plagiostomus seems to be link with a reflex of recovery strategy due to physiological process of gonadal development.

Screening of escherichia coli o157: H7 contamination and nitrate content on butterhead lettuce from market outlets

Escherichia coli O157:H7 is classified as biological hazard that can produce a bloody diarrhea due to its toxins. While nitrate in vegetables is classified as a chemical hazard if ingested greater than limit and risk getting gastrointestinal cancer and methemoglobinaemia. A study was conducted to obtain the information on E. coli O157:H7 contamination and nitrate content in Butterhead lettuce from local suppliers. The number of colonies E. coli O157:H7 from the lettuce was enumerated using standard plate count and the nitrate content was measured using nitrate meter. From the experiment, it was found that E. coli O157:H7 contamination of Butterhead lettuce in Malaysia is still within the safe limit for the consumers while the nitrate content was distributed differently between leaf structures; midrib, outer adult leaf blade and young leaves. Lettuce midrib and outer adult leaf blade had a higher concentration of nitrate compared to the young leaves.

Carbon, nitrogen and phosphorus stoichiometry of rivers in the light of Redfield ratio

Abstract. A. Redfield entered the history of hydroecology due to the discovery of a unique stoichiometric ratio of Carbon, Nitrogen and Phosphorus – 106: 16: 1 – in the marine plankton, which it was later named after the author – the Redfield Ratio. Furthermore, A. Redfield established, that the stoichiometric ratio of Carbon, Nitrogen and Phosphorus in seawater is supported on the average level and it is 1017 : 15 : 1. On the basis of established stoichiometric ratios A. Redfield came to the conclusion that exactly Nitrogen is a limiting factor in the marine environment, because the ratio of its average statistical stoichiometric availability in seawater turned out lower than the average stoichiometric utilization of plankton. Also the merit of A. Redfield is the was established by him the carbon and nitrogen forms, which make the greatest contribution to the pool of these elements are available for plankton. After Redfield the studies by the CNP-stoichiometry of water and plankton in marine and ocean ecosystems were carried out by a number of researchers. However, the CNP-stoichiometry of rivers water fell out of the field of view of hydroecologists. The authors of this publication tried to fill this gap. The purpose of the studies was to establish the peculiarities of CNP-stoichiometry of river ecosystems in comparison with marine ecosystems and it determine the contribution of different forms of carbon and nitrogen to the pool of these elements which available for plankton in river water. The research was conducted during the summer low water period (2014) at the at monitoring stations of watershed of the three rivers of the Carpathian region within the Chernivtsi region. It is Dniester, Prut and Siret. Water samples were taken by a bathometer at 16 sites (near 8 forest and 8 meadow floodplains) of each of the 15 monitoring stations. Under laboratory conditions, the nitrate content was determined by the nitrate meter (H-401). Carbonates and hydrogen carbonates was determined by titrimetrically method. Phosphates, ammonia and nitrites was determined by photocolorimetrically method. Like Redfield, the stoichiometric availability of Сarbon and Nitrogen in river water was estimated as the ratio of the molar concentrations of the corresponding elements to the molar Phosphorus concentration. For the first time the features of CNP stoichiometry of the rivers were installed in comparison with the marine stoichiometry. The stoichiometric ratio of total carbon, nitrogen and phosphorus in river water of the Carpathian region is 938C: 59N: 1P and the ratios of their stoichiometric availability to stoichiometric utilization by plankton is 8,9C : 3,7N : 1P. It was shown that stoichiometric availability of energetically favorable for the assimilation by plankton by forms of carbon and nitrogen – СО2 и NH4+ – in the rivers water is greatly reduced, and do not cover the necessary level of stoichiometric utilization of these elements by plankton. It is proved that the greatest contribution in the river water to the pool of stoichiometric available of carbon and nitrogen contributes HCO3-, а азота – NО3- in accordance. It was found that the main limiting factor of growth of and development of plankton in rivers of the Carpathian region appears phosphorus whose balanced share in CNP ratio is an order of magnitude lower than that it need for the utilization by plankton.

Evaluation of a Rapid Field Test Method for Assessing Nitrogen Status in Potato Plant Tissue in Rural Communities in the Bolivian Andean Highlands

The relatively poor accessibility, high costs, long turnaround time for analysis, and lack of information about soil and plant testing in the Andean highland region (Altiplano) of Bolivia has hampered informed and timely nutrient management decisions for potato (Solanum tuberosum L.) crops. The objective of this study was to determine if the Cardy nitrate meter (Horiba Ltd., Kyoto, Japan), a low-cost, portable, and rapid field test method, could be used to improve nitrogen (N) fertility management among isolated rural indigenous communities at different elevations in this rugged semi-arid environment. Fully matured leaf petioles were sampled at blooming time from potato trials established in three communities during the 2006–2007 and 2007–2008 growing seasons. Those trials were composed of 12 fertility treatments (i.e., an unfertilized control and different combinations of sheep and cow manure, inorganic fertilizer, commercial household/urban compost, and a commercial microbial activator soil amendment) arranged in a randomized complete block design with four replications. In general, in both growing seasons and in all communities, nitrate measured in the sap of leaf petioles by the Cardy meter had relatively low but significant correlations with leaf petiole total N (ranging from r2 = 0.07 to r2 = 0.60 across seasons and communities) and with total fresh tuber yield (ranging from r2 = 0.11 to r2 = 0.50 across seasons and communities). However, some problems were encountered with being able to consistently calibrate the meter with supplied standards prior to each use of the meter. These results indicate that the Cardy ion meter might be an effective tool for potato growers or agricultural professionals working in the Altiplano of Bolivia if further research can be conducted to determine if the meter is consistent for diverse sites in the Altiplano and is practical for the cultural, economic, and environmental conditions of the region.

Nitrate-Nitrogen Sufficiency Ranges in Leaf Petiole Sap of Brassica oleracea L., Pac Choi Grown with Organic and Conventional Fertilizers

Greenhouse experiments were conducted to determine the response of Brassica oleracea L., pac choi to fertilizer rates and sources and to establish optimal soluble nitrogen (N) application rates and nitrate meter sufficiency ranges. Conventional soluble fertilizer was formulated from inorganic salts with a 4:1 NO3-N:NH4-N ratio. Phosphorus (P) was held at 1.72 mm and potassium (K) at 0.83 mm for all treatment levels. The organic soluble fertilizer, fish hydrolyzate (2N–1.72P–0.83K), was diluted to provide the same N levels as with conventional treatments. Both fertilizers were applied at N rates of 0, 32, 75, 150, 225, 300, and 450 mg·L−1. Seedlings were transplanted and fertilizer application began at 18 days. Plants were harvested at 7 weeks (5 weeks post-transplanting) after receiving 15 fertilizer applications during production. Samples of the most recently matured leaves were harvested weekly and analyzed for petiole sap NO3-N and leaf blade total N concentration. Leaf count, leaf length, and chlorophyll content were also measured weekly. Fresh and dry weights were determined on whole shoots and roots. Optimum yield was achieved at the 150-mg·L−1 fertility rate with both conventional and organic fertilizers. Field and high tunnel experiments were conducted to validate the sufficiency ranges obtained from the greenhouse studies. Sufficiency levels of NO3-N for pac choi petiole sap during Weeks 2 to 3 of production were 800 to 1500 mg·L−1 and then dropped to 600 to 1000 mg·L−1 during Weeks 4 through harvest for both conventional and organic fertilizers sources. Total N in leaf tissue was less responsive to fertilizer rate effects than petiole sap NO3-N. Chlorophyll content was not useful in evaluating pac choi N status. These guidelines will provide farmers with information for leaf petiole sap NO3-N to guide in-season N applications.

Nitrogen management of fallow crops in Canadian prairie soils

Karamanos, R. E., Selles, F., James, D. C. and Stevenson, F. C. 2012. Nitrogen management of fallow crops in Canadian prairie soils. Can. J. Plant Sci. 92: 1389–1401. The ability of fallow to supply nitrogen (N) to crops has been questioned, particularly for crops with greater N requirements. A study was conducted to determine canola (Brassica napus L.) and wheat (Triticum aestivum L.) responses to a range of N fertilizer rates (0–75 kg N ha−1 for canola and 0–50 kg N ha−1 for wheat) at 17 fallow sites across Saskatchewan and Alberta, Canada, from 2003 to 2005. Yield and N uptake responses to progressively greater N fertilizer rates were curvilinear for both crops. Maximum yield occurred with 76 kg N ha−1 for canola yield (2190 kg ha−1) and 47 kg N ha−1 for wheat (2910 kg ha−1). Maximum N uptake occurred at about 90 kg N ha−1 for both crops. Wheat grain yield and N uptake responses were mostly associated with normalized difference vegetation index (NDVI) at anthesis or flag leaf, whereas canola yields and N uptake were most associated with NDVI at five-leaf or bolting, or Cardy Nitrate meter at bolting. The preceding relationships were most apparent at the highest N fertilizer rates. Canola and wheat water use were not affected by N fertilizer rate, but water use efficiency increased linearly for both crops as N fertilizer rate was increased.

Monitoring nitrogen nutrition in cotton

Both N excess and deficiency may affect cotton yield and quality. It would therefore be useful to base the N management fertilization on the monitoring of the nutritional status. This study investigated the correlations among the following determination methods of the N nutritional status of cotton (Gossypium hirsutum L., var. Latifolia): chlorophyll readings (SPAD-502®, Minolta), specific-ion nitrate meter (Nitrate Meter C-141, Horiba-Cardy®), and laboratory analysis (conventional foliar diagnosis). Samples were taken weekly from two weeks before flowering to the fifth week after the first flower. The experiment was conducted on the Fazenda Santa Tereza, Itapeva, State of São Paulo, Brazil. The crop was fertilized with 40 kg ha-1 N at planting and 0, 30, 60, 90, and 120 kg ha-1 of side-dressed N. The range of leaf N contents reported as adequate for samples taken 80-90 days after plant emergence (traditional foliar diagnosis) may be used as reference from the beginning of flowering when the plant is not stressed. Specific-ion nitrate meter readings can be used as a nutritional indicator of cotton nutrition from one week after pinhead until the third week of flowering. In this case, plants are well-nourished when readings exceed 8,000 mg L-1 NO3-. The chlorophyll meter can also be used to estimate the nutritional status of cotton from the third week of flowering. In this case the readings should be above 48 in well-nourished plants.

Establishment of Critical Sap and Soil Nitrate Concentrations using a Cardy Nitrate Meter for Two Carrot Cultivars Grown on Organic and Mineral Soil

Nitrate (NO3 −) meters have been used effectively for crop nitrogen (N) management in many crops, including corn and cabbage. The use of a Cardy NO3 − meter to assess the N status of the carrot crop could improve the utilization of applied N, but critical NO3‐N concentrations are required. Two carrot cultivars were grown on mineral and organic soils over 3 years at five N application rates to establish critical sap and soil NO3‐N concentrations and to identify the effects of soil type and cultivar. Although a yield response to N application occurred on mineral soil in 2 of 3 years, consistent critical sap NO3‐N concentrations could not be established because of variability among years, cultivars, and soil types. Critical soil nitrate concentrations were highly variable, but values of 31 to 36 mg · L−1 NO3‐N could be established for the early sampling date to 30 cm deep. Sap NO3‐N concentrations cannot be used alone for N analysis of carrots, but early‐season soil NO3‐N assessment could be useful in adjusting N‐fertilization practices.

Assessment of a Nitrate Meter for Nitrogen Tests in Mineral and Organic Soils

Abstract Nutrient management legislation in Ontario, Canada, has prompted an evaluation of alternative nitrogen (N) management techniques. Rapid, accurate methods of assessing soil nitrogen are required to assist in N management. A portable nitrate (NO3 − meter (Cardy) was evaluated for use in testing soil N for vegetable crops grown on organic and mineral soils. Cabbage, carrots, and onions were grown on both soils in Ontario, Canada, in 2000 and 2001. Nitrogen was applied at five rates to cabbage and carrots, and three rates to onions ranging from 0 to 200% of current provincial recommended N rates. At three growth stages throughout the growing season, soil samples were collected and subdivided. One subsample was used for Cardy meter analysis, and the other for laboratory analysis of NO3-N. Cardy NO3-N readings overestimated laboratory results in most instances on mineral soil, but consistently underestimated laboratory results on organic soil. A conversion factor would be required for both soil types, ...

(224) In Situ N Monitoring for Safe Leafy Vegetables using Quick and Advanced Tools

High levels of N fertilizers are generally applied in intensive leafy vegetable production in the peri-urban agriculture of Southeast Asia. This study was conducted to develop a simple and rapid method of determining nitrate-N accumulation in selected leafy vegetables. Five leafy vegetables, including amaranth (Amaranthus tricolor), kangkong (Ipomoea aquatica), Ethiopian kale (Brassica carinata), choysum (Brassica campestris sp. parachinensis), and leafy lettuce (Lactuca sativa) were grown on raised beds in 32-mesh nethouse in randomized complete-block design with four replications. The crops were fertilized with eight N levels: 0, 50, 100, 150, 200, 250, 300, and 350 kg·ha-1 in three splits. At harvest, nitrate contents were determined in tissue sap of fully expanded leaf blades, petioles and whole plant using a Cardy nitrate meter. Chlorophyll content readings were also measured on the same leaf using a chlorophyll meter. Nitrate accumulations varied with vegetable species. Significant correlations (P< 0.001) existed between N fertilizer rate and nitrate content as well as leaf chlorophyll and yield. Using N application rate of 200 kg·ha-1, nitrate accumulation in Ethiopian kale was highest (7000 ppm), followed by kangkong (4000 ppm), amaranth (3500 ppm), and leafy lettuce (1200 ppm). The correlation between leaf chlorophyll meter reading (LCMR) and nitrate content was also significant (P< 0.001), suggesting the feasibility of using Cardy nitrate meter test and LCMR for monitoring production of low-nitrate and safe vegetables. The Cardy meter was also sensitive in detecting soil nitrate-N below 20 ppm and is a rapid and reliable alternative to conventional distillation method.

Rapid Determination of Nitrogen Status in Pansy

Two experiments were conducted with pansy (Viola ×wittrockiana Gams `Bingo Yello') to determine the relationship between foliar nitrogen (% of dry weight) (FN) and either sap nitrate concentration (SN) in petioles or SPAD readings of foliage. FN was highly correlated to SN throughout both experiments (r = 0.80 to 0.91). FN was poorly correlated to SPAD readings early in both experiments (r = 0.54 to 0.65), but more highly correlated later when visual symptoms of N deficiency were apparent (r = 0.84 to 0.90). SN determined with the Cardy sap nitrate meter was a reliable predictor of FN in pansy, while SPAD readings were only reliable after symptoms of N deficiency were visually evident. FN can be predicted with SN using the following equation: log(SN) = 0.47*FN + 1.6 [r2 = 0.80, n = 132]. Growers and landscape professionals can use SN readings to predict FN levels in pansy, and thus rapidly and accurately diagnose the N status of their crop.

Rapid Determination of Nitrogen Status in Annual Vinca

Abstract Three experiments were conducted to develop a method for rapid determination of nitrogen (N) status in ‘Pacifica White’ vinca (Catharanthus roseus (L.) G. Don). In experiment 1, N was applied to potted vinca at 40, 80, 120, or 160 ppm N to produce plants ranging from N deficient to N sufficient. Data were collected 14, 28, and 42 days after treatment (DAT) and included flower number, growth index [(height + width + width) ÷ 3], and from recently matured foliage the following parameters: SPAD-502 readings, petiole sap nitrate (SN) concentration, and total-N (percent of dry weight) (FN). Experiment 2 was similar with the exception that N rates applied were 30, 60, 90, 120, 150, or 180 ppm N, and data were collected 14, 29, and 42 DAT. In experiment 3, N was applied at 0, 90, or 180 ppm N and data were collected 0, 4, 7, 10, and 14 DAT. In experiments 1 and 2, SPAD readings were poorly correlated to FN (correlation coefficients ranged from 0.35 to 0.88) and the relationship between FN and SPAD readings changed at different collection dates. Petiole sap nitrate concentration determined by a Cardy nitrate meter was highly correlated throughout the three experiments. Above 380 ppm SN, the relationship between FN and SN was determined to be: SN/1000 = 2.3 × FN-4.8 (r2 = 0.73, n = 104). In experiment 3, FN and SN readings were able to detect N deficiency in vinca by 4 DAT, despite lack of visual symptoms until 14 DAT. SPAD readings were not suitable for predicting FN and plant N status. SN was a reliable predictor of FN and thus could be used to rapidly determine plant N status.

Quick nitrate test for hybrid sudangrass and pearlmillet Hays

Hybrid sudangrass and pearlmillet are noted as having a high potential for accumulating nitrate (NO3) and poisoning cattle. Hay samples can be accurately tested for NO3 content in the laboratory, however, this may take considerable time for farmers to obtain their results. This study was conducted to evaluate applicability of a quick Nitrate Meter for in‐field testing of forage NO3 in the plant sap and to study the effects of nitrogen (N) fertilization on forage NO3 accumulation. Nitrate readings taken from the sap were highly correlated with those using the conventional laboratory method (R2=0.85–0.95 for hybrid sudangrass and 0.91–0.94 for pearlmillet). Nitrate concentrations varied with plant height, growing stages, locations in the test plots, N rates and sources, and environmental conditions. Nitrate concentrations in the whole plant decreased with plant height and plant maturity. Higher NO3 levels were correlated with higher rates of N fertilizers. Nitrate accumulation was also enhanced by drought stress. The quick NO3test method is easy to use and usually takes less than 20 minutes to obtain results. This methodology allows increased management flexibility for farmers who use warm‐season annual grasses in their production systems.

Sap analysis for diagnosis of nitrate accumulation in cereal forages1

Development of a quantitative, preharvest quiektest for NO3 levels in cereal forages would improve crop management options to avoid NO3 toxicity in livestock. Our objective was to determine if concentrations of NO3 in sap expressed from oat (Avenasativa) and barley (Hordeum vulgare) are correlated with those in dry tissue of simultaneously harvested hay, and to test the reliability of the Cardy portable NO3 meter for sap analysis in these species. In 1993, whole plant samples were gathered from plots fertilized with variable nitrogen (N) rates at four environments in Montana, and were analyzed for NO3 concentration in lower‐internode sap and in whole plant dry matter. In 1994 and 1995, the study was repeated at two environments. The sampling technique included three subsamples from each plot for sap analysis, followed immediately by harvest of the entire plot for hay, and further subsampling for dry matter NO3 analysis after drying. Linear correlations between dry matter and sap NO3 concentrations were found across species at each environment in 1993 with r values of 0.64 to 0.81. No relationship was established for oat at one environment. Locations differed in the coefficient of correlation, indicating environmental influences on the relationship and/ or variability due to sampling technique. In 1994 and 1995, each species fit a separate linear correlation across site‐years with r values of 0.89 (oat) and 0.87 (barley). The consistency across site‐years (1994–1995) indicates that the variability in preliminary results was overcome with sampling technique. We propose a quantitative quiektest for NO3 levels in cereal forages using conditional predictions of dry matter NO3 based on observed values of sap NO3. Since sap NO3 readings with the Cardy portable nitrate meter were well correlated (r=0.93) with Accumet ISE readings across critical ranges, quiektest procedures are practical.

A petiole sap nitrate test for broccoli

Nitrogen (N) status of vegetable crops is often monitored by analysis of dried plant tissues. However, dry tissue analysis often causes a significant delay between sampling and analysis. This study was conducted to examine the accuracy of a portable nitrate meter for determining petiole sap nitrate (NO3) contents, and the relationship between NO3‐N concentration in fresh petiole sap and in dried petiole tissue of broccoli grown in southern Arizona during the 1993–94 and 1994–95 winter growing seasons. Experiments were factorial combinations of three irrigation rates and four N rates, both ranging from deficient to excessive. Petioles were sampled throughout each season, and split for sap and dry tissue analysis. A linear correlation was obtained between the two measurements in both seasons, with no consistent effect due to irrigation treatment or crop maturity. The regression coefficients did not differ among seasons. Therefore, a combined regression equation: Y=343+0.047X (r2 = 0.799) was derived, in which Y=NO3‐N (mg/L) in fresh petiole sap, and X=NO3‐N (mg/kg) in dried petioles. These results suggest that the sap test can be a valuable and rapid technique to predict N needs of broccoli. Differences between the two methods are likely due to interferences in fresh petiole sap and slight differences in pools of extracted NO3.

Nitrogen Management of Drip-iIrrigated Peppers

Inadequate N can reduce growth and yield, but excess N can be uneconomical and environmentally harmful. Our objective was to investigate the potential for using fertigation and on-farm plant-nutrient monitoring to improve the efficiency of N fertilizer use by bell peppers (Capsicum annuum L.). Two N fertilizer treatments were compared: 1) all N applied preplant and 2) one-third of the N applied preplant and the remainder injected into the drip-irrigation lines throughout the growing season. Total application rates were N at 118 kg·ha–1 for both treatments. Data were collected for total yield, marketable yield, and fruit size. Leaf and petiole samples were collected every 2 weeks and were used to monitor plant N status throughout the growing season. A Horiba/Cardy nitrate meter was used to measure nitrate concentrations in freshly-pressed petiole sap. A SPAD chlorophyll meter was used to measure leaf chlorophyll content and give an indirect measure of leaf N concentrations. Subsamples of leaves and petioles also were saved for conventional laboratory analyses. Whole (aboveground) plant samples were collected every 2 weeks, analyzed, and used to calculate differences in N accumulation. Suction cup samplers were installed at the 24-in soil depth and water samples collected every 1 to 2 weeks for nitrate analysis. Except for early in the growing season, petiole sap nitrate and leaf chlorophyll were higher in the fertigation treatment. Plant dry matter and total N accumulation also were much larger, but fertigation did not increase yield. Nitrate leaching was greater early in the season with 100% preplant N, but later in the season it was greater with fertigation. Data suggested that adequate plant N, reduced nitrate leaching, and equivalent yields are possible with fertigation at reduced N-rates compared to 100% preplant fertilizer applications.

Comparison of Specific Electrode Techniques for Measuring Bell Pepper Petiole Sap Nitrate Concentration

Sap nitrate was determined with the ion-selective electrodes, HACH combination nitrate electrode, and the CARDY nitrate meter on pepper petioles over five sample dates (n = 160). The electrode values were compared to the Cd reduction method performed on a Lachat automated ion analyzer with flow injection analysis. Thirty petioles were collected from plots of each of several N rate studies and the sap expressed by a hand-held garlic press. Correlation among the techniques were similar (r > 0.9), but the CARDY meter constantly read 100 to 175 ppm higher than the HACH. Across all dates the standard deviation of the difference, compared with the Cd reduction, for the HACH = 16 ppm, while for the CARDY it was 50. While the CARDY meter is easier to use and has fewer steps, the HACH electrode values were closer to the true readings and less erratic. One must use care when interpreting nitrate sufficiency value ranges with different quick-test techniques.

Comparison of Specific Electrode Techniques for Measuring Bell Pepper Petiole Sap Nitrate Concentration

Sap nitrate was determined with the ion-selective electrodes, HACH combination nitrate electrode, and the CARDY nitrate meter on pepper petioles over five sample dates (n = 160). The electrode values were compared to the Cd reduction method performed on a Lachat automated ion analyzer with flow injection analysis. Thirty petioles were collected from plots of each of several N rate studies and the sap expressed by a hand-held garlic press. Correlation among the techniques were similar (r > 0.9), but the CARDY meter constantly read 100 to 175 ppm higher than the HACH. Across all dates the standard deviation of the difference, compared with the Cd reduction, for the HACH = 16 ppm, while for the CARDY it was 50. While the CARDY meter is easier to use and has fewer steps, the HACH electrode values were closer to the true readings and less erratic. One must use care when interpreting nitrate sufficiency value ranges with different quick-test techniques.