Prediction of nitrogen fertilizer requirement in cotton using petiole and sap nitrate

Abstract

With the aim of refining methods of determining plant N status of cotton, we measured nitrate concentrations in petioles and xylem sap in field experiments over three seasons. Main plots were rotation/tillage treatments which were split for fertilizer N. Petiole nitrate concentration was about 30 g N/kg at appearance of flower buds (squares). Rotation and N rate had highly significant effects on petiole nitrate concentration in every season. There was a linear decline in petiole nitrate with stage of development (measured in day degrees, base 12°C), particularly between 600 and 900 day degrees from sowing.

The relationship between fertilizer N requirement and petiole nitrate concentration was exponential, with greatest precision when high fertilizer rates were required. The relationship between fertilizer N requirement and the rate of decline in petiole nitrate was linear, giving equal precision over the N fertilizer range. Optimum plant N status was represented by a petiole nitrate concentration of 21.5 g N/kg at 750 day degrees from sowing, or by a rate of decline in petiole nitrate of 0.0318 g N/kg/day degree. We conclude that the interpretation of petiole nitrate data could be improved by considering the rate of decline in petiole nitrate around flowering, particularly for sites where only moderate amounts of N are required. Concentrations of nitrate in xylem sap were highly correlated with petiole nitrate, but were more variable. For this reason, we concluded that petiole analysis was the superior diagnostic test.     

Evaluation of a rapid sap nitrate test for young kiwifruit vines

Abstract

A glasshouse experiment was conducted with young grafted kiwifruit plants to evaluate a rapid sap nitrate test using Merck nitrate test strips, and to establish critical values for maximum vine growth. Total N leaf concentration for these plants was also related to vine growth. Sap nitrate nitrogen was significantly related to growth of the plant expressed as unit leaf rate (ULR) over four and six week periods from the time of sampling. Total N, on the other hand, was only significantly related to the total cane length at the time of sampling but not to the ULR. Using Cate‐Nelson graphical method, the critical sap NO₃‐N value for maximum growth was established at 500–600 ppm. The critical value for total N was established at around 3.2%.     

Nitrogen application rates for greenhouse tomato based on real-time diagnosis of petiole sap: Effects of soil nitrate contents before cultivation

(pp. 825–831)

This study was carried out to clarify the effects of soil nitrate before cultivation and amounts of basal-dressed nitrogen on additional N application rate and yields of semi-forced tomato for three years from 1998 to 2000. The amounts and timing of additional N dressing were determined based on diagnosis of petiole sap nitrate. The top-dressing was carried out with a liquid fertilizer when the nitrate concentration of a leaflet's petiole sap of leaf beneath fruit which is 2–4 cm declined below 2000 mg L^?1.

For standard yield by the method of fertilizer application based on this condition, no basal-dressed nitrogen was required when soil nitrate before cultivation was 150 mg kg^?1 dry soil or higher in the 0–30 cm layer; 38 kg ha^?1 of basal-dressed nitrogen, which corresponds to 25% of the standard rate of fertilizer application of Chiba Prefecture, was optimum when soil nitrate before cultivation was 100150 mg kg^?1 dry soil; 75 kg ha^?1 of basal-dressed nitrogen, which corresponds to 50% of the standard, was optimum when soil nitrate before cultivation was under 100 mg kg^?1 dry soil. A standard yield was secured and the rate of nitrogen fertilizer application decreased by 49–76% of the standard by keeping the nitrate concentration of tomato petiole sap between 1000–2000 mg L^?1 from early harvest time to topping time under these conditions.     

Effect of restricted supply of nitrate on fruit growth and nutrient concentrations in the petiole sap of tomato cultured hydroponically

Tomato plants (Lycopersicon esculentum Mill. cv. Momotaro) were cultured in nutrient solution supplying 35 meq or 50 meq of nitrate (NO₃) per plant weekly from the flowering stage of the first truss in two cropping seasons. The effects of NO₃ supply levels and cropping season on fruit growth of tomato were investigated. Furthermore, the relationship between the results of the plant sap analysis and fruit growth of tomato was analyzed. In the spring to summer cropping, NO₃ supplied was almost all absorbed and high productivity of tomato fruits was obtained in each treatment. In the fall to winter cropping, however, high NO₃ supply did not increase the uptake of NO₃, but tended to decrease the rate of fruit set and marketable yield. Accumulation of NO₃ in the petiole sap was found with high NO₃ supply in the fall to winter cropping. Cropping season greatly influenced not only fruit growth but also the concentration of NO₃ in the petiole sap in relation to the ability of tomato plants to use available nitrogen (N). Furthermore, reduction in the rate of fruit set and weight of tomato fruit were found to relate to the low concentration of NO₃ in the petiole sap of the leaf just below this fruit truss. High NO₃ supply tended to increase potassium (K) concentration and electrical conductivity (EC) value, and to decrease phosphate (P), calcium (Ca), and magnesium (Mg) concentrations in the petiole sap. On the whole, concentrations of these elements in the petiole sap consistently reflected their uptake rates in two cropping seasons.     

Potato nitrogen management by monitoring petiole nitrate level

Petiole nitrate nitrogen (NO₃‐N) concentrations have been successfully used in Northwestern New Mexico to make timely nitrogen (N) recommendations for irrigated potatoes. However, a quick test and consistent sampling time is needed to precisely determine fertigation and to prevent over fertilization, especially in sandy soils. This study examined the petiole NO₃‐N dynamics during the growing season for both chipping and table stock varieties. Readings from a quick in‐field sap NO₃‐N meter were highly correlated with NO₃‐N indications using the conventional laboratory method. The sap NO₃‐N meter can significantly reduce testing turnaround time and has great potential for potato N management. Results showed that most consistent NO₃‐N readings could be obtained by collecting tissue samples between 1100 and 1400 hours of the day.     

Sampling variability of petiole nitrate in irrigated cotton

Abstract

Sampling variability of petiole nitrates was evaluated on commercial, furrow‐irrigated cotton fields in southern Arizona. Analysis of individual petioles shows that sampling from the first mature leaf is best and when the maturity of the leaf is in question, it is better to sample the next older leaf. Field sampling methods used by a growers’ association were evaluated and confidence levels of their estimations were determined.     

Evaluation of a rapid method for plant sap nitrate analysis

Abstract

A rapid method of analysis of nitrate in plant sap using Merck test strips was evaluated. Accuracy and precision of the strips was found to be acceptable in a test in which aqueous samples were tested by four operators. Nitrate N was measured in five vegetable crops at two stages of growth by two methods: squeezing sap from fresh petiole or stem tissue with NO3‐N determination by Merck test strip; and acetic acid extraction from dried petiole or stem tissue with NO3‐N determination by autoanalyser. The relationship between the two methods was found to be highly significant with coefficient of determination exceeding 0.82 in eight out of 10 cases (crops x sampling dates). When the strip results were corrected for moisture content the relationship with the laboratory method improved in most cases.     

Nutritional changes in petiole sap over space and time in a tomato crop greenhouse

The aims of this trial were to determine the spatial and temporal variability of the nutrients in petiole sap in a tomato crop under greenhouse and to determine the number of sub-samples for a representative sample. The experiment consisted of the selection of 20 sampling points. Petiole of fully expanded leaf was collected weekly in order to determine Cl, NO₃-N, H₂PO₄-P, SO₄-S, Na, K, Ca and Mg concentrations. Our results showed that variations of NO₃-N, Na, Ca and K concentrations in sap were affected by the spatial distribution, whereas SO₄-S and Mg concentrations in sap were affected by their temporal distribution. The spatial variability of our experiment could be related to radiation, yield and antagonism between nutrients, whereas the time variability could be related to the phenological stage of the plant and the antagonism between nutrients. The suggested number of petiole sub-sample ranging from 25 to 113 depending on nutrient.     

Anionic relationships in leaf petiole sap of tomato and capsicum plants growing in a glasshouse

The nitrate, chloride and sulphate content and their interaction effects in capsicum and tomato plants growing in glasshouse under fertigation systems was studied. Using leaf petiolesap concentrations as an index of the uptake rhythm, it was found that nitrate‐chloride and nitrate‐chloride plus sulphate relationships are regulated by potential or logarithmical laws. Nitrate‐sulphate interactions only appear clear in capsicum plants, but not for tomato.

The utilization of these interaction curves may permit the use of waters with a relatively high saline level for the irrigation of the both capsicum and tomato plants, by suitable planning of the nitrate supply in the fertigation program.     

Rapid and simple leaf tissue test for nitrate

Abstract

A simple and rapid procedure for the determination of nitrate in fresh leaf tissue, suitable for use by relatively untrained operators is presented. The method requires only 4 reagents and can be carried out in less than 20 min from start to finish. A 400 mg sample of fresh leaf tissue is macerated briefly with 5 drops of 10 N sulphuric acid, diluted with 10.0 ml of water and filtered. Nitrate‐N is estimated on an aliquot of the filtered extract by reducing the nitrate to nitrite by shaking with powdered zinc in ammonium hydroxide solution for 3 min. The reduced mixture is allowed to settle (5 min) and an aliquot is withdrawn through a cotton‐wool plug thus removing any particles of the zinc. The filtered aliquot is then reacted with a single colour reagent to yield a pink azo‐dye, the intensity of which is directly proportional to the amount of nitrate.

The method was found to have a coefficient of variation of about 4%. When compared with the phenoldisulphonic acid method for nitrate, on aliquots of the some plant extract, it yielded values which were on average 94.6% of those obtained with the former method. The coefficient of variation between the methods was 7%.     

Quick nitrate test for hybrid sudangrass and pearlmillet Hays

Abstract

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.     

Monitoring sap nitrate in vegetable crops: Comparison of test strips with electrode methods,and effects of time of day and leaf position

Abstract

A field crop of 3‐month old cabbages was sampled every 2 h from 0600 h until 2000 h. At each sampling, an upper, middle and lower leaf were taken from four plants, and their petiole nitrate status measured by three methods (a) “Merckoquant”; test strips (b) specific ion electrode on a fresh macerated extract and (c) the same electrode on an extract of oven dry tissue. All three methods led to similar conclusions: a. there were very big differences in concentration with leaf position, the middle leaf having the highest;

b. there were large concentration differences between plants, especially for the lower leaves;

c. the effect of time of day was not significant.

The test strips are capable of giving satisfactory results provided that sufficient plants are sampled, but values thus obtained for sap may be lower than for macerated fresh tissue, especially at the low end of the concentration range.     

Correlation of petiole sap nitrate-nitrogen concentration measured by ion selective electrode,leaf tissue nitrogen concentration,and tomato yield in Florida

The effectiveness of measuring petiole sap nitrate-nitrogen concentration (PSNC) using ion selective electrode (ISE) has been scrutinized due to claims that PSNC poorly predicts leaf tissue nitrogen concentration (LTNC) or crop yield. This study evaluated the relationship among PSNC, LTNC, and marketable yield of tomato (Solanum lycopersicum L.). Two tomato trials were conducted using seepage irrigation and controlled-release fertilizer (CRF) in fall 2011 and 2012. At 15 days intervals, six most recently mature leaves were collected to measure PSNC and LTNC. PSNC and LTNC declined throughout the growing seasons, but PSNC was affected by weather. PSNC and LTNC were correlated (P = 0.0001, r = 0.38), though not meaningfully. PSNC and LTNC correlated negatively and positively with crop yield in most correlations, respectively. Correlations of CRFs and soluble fertilizers (SFs) separately, did not improve relationships. Measuring LTNC may be a more reliable nutrient management tool compared to PSNC measured using an ISE.     

Field sampling considerations for the stem nitrate test in peppermint

Abstract

The stem nitrate test for peppermint (Mentha piperita var.) is a promising nitrogen (N) management tool. When used properly, this test may aid in obtaining significant savings of fertilizer costs and in the protection of groundwater quality. There are several factors related to environmental conditions, N management, and sampling procedures that have not been evaluated and may confound interpretation of test results. The objective of this study was to measure the response of stem nitrate concentrations to factors that would be expected to influence the test and develop guidelines for the collection of stem tissue. The factors considered here were i) solar radiation effects on both hourly and daily scales; ii) spatial variability; iii) differences between alternative plant materials; and iv) the temporal response of tissue nitrate concentrations to soluble N application. The most influential of these variables were the type of stem material (a 441% effect at p=3.55E‐6) and the number of stems collected to estimate the field mean concentration. It was found that the variance of the sample population and the number of stems required for a given sampling error could be greatly reduced by only collecting stems from within the plant canopy. Collecting only these stems, 30 stems were found to be adequate to estimate the field mean concentration within 10 to 15% of the true population mean (p<0.05). Statistically significant differences in stem nitrate concentrations were produced by variations in solar radiation on both hourly (p<0.05) and day length (p<0.01) scales. When measuring the diurnal response, a 17% reduction in stem nitrate concentration was observed over a nine‐hour period from 12:00 hours to 21:00 hours. On the day length scale, an 80% reduction in incoming solar radiation produced a 29% increase in stem nitrate concentrations after three days of shading. In the analysis of stem nitrate spatial variability, no discernable range of autocorrelation was detected indicating a purely random distribution of stem nitrate concentrations on the l‐150mscale. Given this finding and under the conditions of the analyses (late season with stem nitrate in excess of critical levels), it is not important that samples collected for this test fully cover the field being assessed, despite the intuitive appeal of full‐field sampling as a standard procedure. The response of stem nitrate concentrations to soluble N application was minimal, probably due to plant N status in the test plots being well above the critical deficiency content prior to application. With the data produced from these investigations, users of the peppermint stem nitrate test are presented with a method to collect data in the field whereby N management interpretations of the test can be more consistent and reliable. In addition, these results indicate the need for researchers to fully report the method of sampling employed when presenting finding for stem tissue tests.     

Nitrogenous constituents of bleeding sap from taro plants grown in nitrate nutrition under a potassium deficiency

The previous work (1) with bleeding sap from taro plants grown in solution culture at varying ammonium sulphate application under aerobic condition revealed that a potassium deficiency led to a contradictory relationship of the variation in amino-N content in bleeding sap to the exudation rhythm; in the earlier period of bleeding experiment a deficient K-application decreased the amino-N content but accelerated the exudation rate. In this connection, there are good reasons for believing that the passage of water and salts into the xylem ducts is largely controlled by the metabolic conditions in adjacent living cells, especially their rate of aerobic respiration (2). Therefore, the effects of potassium nutrition on the exudation phenomenon were reexamined with taro plants grown in solution culture under nitrate nutrition and correlated with information about the effect of aeration through culture medium during bleeding experiment on the rate of exudation and contents of nitrogenous constituents of bleeding sap. Arsenite- or DNP-treatment was also carried out in vivo with the roots in order to elucidate a possible relationship between the respiration in roots and the exudation process of xylem sap.     

A laser-diode-based system for measuring sap flow by the heat-pulse method

Transpiration, the movement of water through plants from the soil to the atmosphere, is an important process in plant physiology, the hydrologic cycle, and the global energy balance. Transpiration at the scale of individual plants can be measured with weighing lysimetry, but this technique is limited to small plants and is generally impractical for trees and many field crops. Heat-pulse velocity methods offer an alternative, and several plant sap flow gauges have been marketed. Because these gauges use electrical resistance heaters to heat the stem, they present several problems: they are invasive, typically bulky, provide poor temperature control (killing the cambium), and have lengthy response times, so they cannot measure short-term transients.In this report, we describe a system for measuring sap flow in real-time and without the need to puncture the stem. Instead of a resistance heater, it uses a laser beam as a heat source, and instead of contact thermometers, it uses non-contact infrared thermometers. Used with a precision-mounting unit that insures constant alignment, it determines whole-plant transpiration. The laser has the added advantage of delivering a precisely controlled amount of heat for a discrete time period. The end product is a more accurate, less invasive way to gauge water flow through herbaceous plant stems.     

Blade or petiole analysis as a guide for grape nutrition

Abstract

The leaf opposite the first fruit cluster was used for the investigation of grape nutrition at bloomtime and ripening. The data show that blade analysis and petiole analysis are both suitable for the assessment of the nutrient status in the case of P, K, Mg and Ca. However, the data obtained for nitrogen differ markedly, depending on the organ considered.

For phosphorus and potassium, the differences in nutrient content between vineyards as well as the seasonal variations are better reflected by petiole analysis. This effect, which should be favourable to the diagnosis, is paralleled by a wider scattering of the nutrient levels; as a result, the differences observed in the petiole are not statistically more significant than those in the blade.

Under relatively homogeneous conditions (same variety, same climate), the differences induced by variable parameters (soil type, sampling times, years) appear to be fluctuating, so that nutrient reference levels cannot be recommended, whether for the blade or the petiole. Both sampling modes (blade or petiole) are complementary to each other and could therefore be used advantageously for a better control of grape nutrition and fertilization.     

Germination-enhancing and zinc-sparing roles for selenium in broccoli

Large areas of China have soils low in both available selenium (Se) and zinc (Zn). In order to investigate whether Se supplied as either selenate or selenite can increase germination and growth compared with low-Se controls we used broccoli, an important vegetable with anticancer effects, especially when biofortified with Se. Broccoli was grown under both Zn adequacy and Zn deficiency to determine whether interactions between these minerals affect plant growth. Selenite and selenate at a wide range of doses increased the speed and extent of germination. Both inorganic Se forms increased early root and shoot growth at low concentrations, with selenite having a stronger effect than selenate. A sand culture trial showed a similar growth increase due to low-dose Se under Zn deficiency but not under Zn adequacy. Conversely, at high Se levels, the results provided evidence from biomass, water use, photosynthesis and gas exchange that broccoli growth was inhibited at high Se levels, with selenite being more toxic than selenate. In this broccoli trial, the two Se forms were equally effective in increasing leaf Se concentration, whereas in most plants selenite is largely converted to organic Se forms and stored in the roots. This study suggests that Se, supplied either as selenate or selenite, may improve germination and growth in broccoli, especially on Zn-deficient soils. Field trials conducted on soils which are very low in both plant-available Se and Zn are needed.