Sap Nitrate Research Articles

054 RESPONSE OF STRAWBERRY TO N FERTILIZATION BY DRIP IRRIGATION

During the 1992-93 fruiting season, strawberries were fertigated weekly with 0.28, 0.56, 0.84, 1.12, or 1.40 kg N/ha/day from ammonium nitrate. K was applied uniformly at 0.84 kg/ha/day by fertigation. Irrigation maintained soil moisture tension in the beds between -10 and -15 kPa. Fruit yields responded positively to N fertilization with yields maximized at 0.56 kg N/ha/day. Leaf N and petiole sap nitrate N concentrations increased with N rate with leaf-N for the plants receiving 0.28 kg N/ha/day remaining below 25 g·kg-1 most of the season. Sufficiency ranges for petiole sap nitrate-N quick testing were developed.

Kinetics of soil‐plant nitrate relations in potato and peppermint: A model for derivative diagnosis

Abstract Suitable plant diagnostic procedures for nitrogen (N) management in high input crops such as potato (Solanum tuberosum) and peppermint (Piper mentha) should be derivative [measuring instantaneous nitrogen (N) uptake] rather than integrative (total accumulation) and should reflect concurrent soil N availability. Analyses for dry matter or sap nitrate (NO3) in potato petioles or peppermint stems are proposed as derivative procedures, but the plant‐soil NO3 relations of these analyses are not well understood. Our objectives were to test the validity of these derivative plant diagnoses as measures of concurrent uptake against the Michaelis‐Menten model of saturation kinetics. Periodic measures of dry matter and sap NO3 in potato petioles and peppermint stems were taken from field experiments with various rates and timings of N fertilizer, and regressed against concurrent soil NO3 (0–30 cm) by nonlinear least squares fit to the model: V = (Vmax · SN)/(Ks + SN) where: V = potato petiole or peppermint s...

Petiole sap nitrate is better than total nitrogen in dried leaf for indicating nitrogen status and yield responsiveness of capsicum in subtropical Australia

This study was conducted to assess the usefulness of petiole sap nitrate and total nitrogen (N) in dried leaf for determining N status and yield response in capsicum (Capsicum annuum L.) grown with plastic mulch and trickle irrigation in subtropical Australia. Five rates of N (0, 70, 140,210, 280 kg/ha) were applied in factorial combination with 2 rates of potassium (K: 0, 200 kg/ha) in randomised block experiments to capsicum cv. Bell Tower grown at Bundaberg Research Station in spring 1990 and autumn 1991. Critical nutrient ranges for nitrate concentration in petiole sap and for total N concentration in dried youngest mature leaf blades plus petioles (YMB + P) were derived at different stages of crop development (bud development, BD; first anthesis, FA; 80% flowering, F; fruit set, FS). Sap nitrate was about 5 times more sensitive to changes in N application than total N. Petiole sap nitrate accounted for a greater amount of the variation in marketable fruit yield (quadratic square root relationships, 0.45 < R2 < 0.83) than total N concentration in dried YMB + P (linear relationships, 0.29 < R2 < 0.74). Simple linear regressions indicated a stronger relationship between applied N and petiole sap nitrate concentration than total N concentration in dried YMB + P (range in R2 values among 8 sampling events: 0.71-0.91 for petiole sap nitrate, 0.35-0.78 for YMB + P total N). For the fertiliser application strategy, 60% of N was applied pre-fruitset and 40% after. Sap nitrate concentrations associated with 95 and 100% of maximum marketable fruit yield increased from BD (5010-6000 mg/L spring, 4980-5280 mg/L autumn) to FA (6220-7065 mg/L spring, 555M000 mg/L autumn). After FA, the range progressively decreased to 1640-2800 and 520-1220 mg/L at FS, for spring and autumn, respectively. It was concluded that petiole sap nitrate was a better indicator of plant N status and yield response than total N concentration in dried YMB + P for capsicum in subtropical Australia. A critical petiole sap K concentration (corresponding with maximum yield and at which no yield response to K addition was measured) of >4800 mg/L was proposed by correlating sap K with yield responses.

FIELD CHLOROPHYLL AND PETIOLE SAP NITRATE INDICATE THE NITROGEN STATUS OF POTATO VARIETIES

We report field experiments, under N limiting conditions, where applied N was varied between 0 and 252 Kg/ha. Two varieties (Castile and Allegheny) were planted in 1990 and 3 varieties (Katahdin, Monona and Superior) were planted in 1991. A curvilinear tuber yield response to N rate was obtained both years for all varieties with maximum yields at about 168 Kg/ha of N. Weekly field measurements with a hand-held chlorophyll meter (Minolta SPAD 502) were highly correlated to yield, to fresh petiole sap nitrate, to dry petiole nitrate and to the total N of whole leaves, all of which were generally highly correlated to each other and markedly affected by applied N. As plants matured the chlorophyll readings, and concentrations of nitrate and N decreased. In general variety differences or variety × N rate interactions were not significant which encourages the use of such tests to avoid unnecessary N sidedressings.

Direct measurement of petiole sap nitrate in potato to determine crop nitrogen status

Abstract Rapid determination of crop nitrogen (N) status in the field would facilitate the use of plant tissue testing as a tool for ? management in potato (Solarium tuberosum L.). The Cardy portable nitrate (NO3) meter may provide the means for on‐site determination of petiole sap NO3 (PSN) concentration. Our objective was to establish the relationship between Cardy meter readings of PSN and laboratory measures of petiole dry matter NO3 (PDMN). In a two‐year replicated field study in western Montana, ‘Russet Burbank1 potatoes were grown under a line‐source sprinkler irrigation system with ? fertilization treatments of 0 ? or a rate of 270 kg N/ha applied in four different timing schemes. This created a wide range in crop ? and water status. Petiole samples were collected at five or six dates each year. Subsamples were analyzed for PSN in expressed sap using the Cardy NO3‐specific electrode or for PDMN with a benchtop NO3‐specific electrode after extraction with a solution of aluminum sulfate [A12(SO4)3]. Petiole sap NO3 levels were highly correlated (r = 0.956** in 1990 and 0.971** in 1991) with PDMN. No significant differences in intercept or slope of the regression equations were detected between the two years. The combined regression is: PDMN (%) = 0.00118xPSN(ppm) ‐ 0.380, r = 0.962** where both variables are expressed on a NO3‐N basis. Independent calibration from Minnesota agreed very closely with these results. Criteria for the use of PSN in potato ? management can therefore be calculated readily from established PDMN criteria.

SAP NITRATE TESTING FOR IMPROVED NITROGEN MANAGEMENT ON POTATOES

A procedure for rapid determination of nitrate in the fresh petiole sap using an ion specific electrode was developed. A highly significant correlation (R2-0.92) was obtained between the nitrate measured by the sap test and the conventional oven-dried tissue method. The effects of five nitrogen(N) rates ranging from 0 to 268 kg ha-1, and five dates of sampling dates beginning at tuber initiation, on the sap nitrate concentration were investigated. The nitrate level increased in proportion to N fertilizer rate. The nitrate level was generally higher at tuber initiation and decreased as the season progressed. The rate of decrease was related to the N supply in the soil. At N rates of 0 and 67 Kg ha-1, the average weekly decrease in the nitrate level was greater than 100 ppm. Based on yield response, the nitrate levels were partitioned as deficient adequate and excessive, and a critical nutrient range was established. The sap test offers a tactical approach for corrective in-season fertilization and a means to increase the efficiency of both fertilizer and available soil N.

Determination of critical nitrogen concentrations of lettuce (Lactuca sativa L. cv. Montello) grown in sand culture

A gamma x cubic response surface model was used to predict the dry matter yield of lettuce cv. Montello over the 8-week growth period in sand culture with nitrogen (N) levels of 2, 5, 11, 18 and 36 mmol/L. At 1, 2, 3, 5, 7 and 8 weeks after transplanting, dry matter yield relative to maximum was plotted against tissue N concentration to derive diagnostic concentrations of petiole sap nitrate-N and leaf total N in youngest fully opened leaf (YFOL), youngest fully expanded leaf (YFEL) and oldest green leaf (OL), and total N in bulked leaf samples. Critical concentrations corresponding to 90% maximum yield are presented. Growth was consistently depressed at 2 mmol N/L due to N deficiency, and at 36 mmol N/L due to salt toxicity. Petiole sap nitrate concentrations were more responsive than leaf total N concentrations to N application levels. Leaf N concentrations at N application levels of 18 and 36 mmol/L were often similar. Critical leaf total N concentrations in YFOL and YFEL decreased from 2 weeks after transplanting to maturity, whereas the opposite trend occurred for petiole sap nitrate concentrations. Critical total N concentration ranges in YFEL were 0.30-0.95 g/L for petiole sap nitrate-N, and 4.00-5.30% for leaf total N concentration. Critical leaf total N and petiole sap nitrate concentrations clearly differentiated between inadequate and adequate N application rates. Critical values in most cases, differentiated toxic concentrations. Nitrogen application levels of 2 and 36 mmol N/L reduced (P<0.05) potassium, calcium and magnesium concentrations in all leaves. This confirms the importance of optimising N supply when determining critical levels of these nutrients for lettuce. Petiole sap nitrate-N concentrations, which can be determined rapidly in the field, can be used to distinguish between a deficient and an adequate N supply. The marked increase in critical concentration over the growth period requires consecutive determinations to verify the N status of lettuce.

Determination of critical nitrogen concentrations of potato (Solanum tuberosum L. cv. Sebago) grown in sand culture

A gamma x cubic response surface model was used to predict the dry matter yield of potato cv. Sebago over the 12-week growth period in sand culture with nitrogen (N) levels of 2, 7, 14, 29 and 43 mmol N/L. At each 2-week sampling period after emergence, dry matter yield relative to maximum was plotted against tissue N concentration to derive diagnostic petiole, petiole sap, leaf nitrate-N and leaf total N in youngest fully opened leaf (YFOL), youngest fully expanded leaf (YFEL) and oldest green leaf (OL) and for total N in bulked leaves. Critical concentrations corresponding to 90% maximum yield are presented. Tissue nitrate was much more responsive than leaf total N to applied N over the 2-14 mmol/L range where positive growth responses to N were recorded. Plants grown with 2 mmol N/L were severely N deficient and growth was depressed. Tissue nitrate concentrations in these plants from 4 weeks after emergence onwards were negligible, while leaf total N concentrations exceeded 2.36%. Salt toxicity occurred at 29 and 43 mmol NIL, and it sometimes reduced tissue N concentrations so that adequacy and toxicity concentrations overlapped. Critical tissue N concentrations declined over the growth period, the largest decline occurring for nitrate. Critical tissue N concentrations for YFEL, from 2 weeks after emergence to final harvest were: petiole sap nitrate-N, 1.2-0.2 g/L; petiole nitrate-N, 2.1-0.1%; leaf nitrate-N, 0.44-0.08%. Critical tissue nitrate concentrations clearly differentiated between inadequate and adequate N application levels. Critical leaf total N concentrations only differentiated between inadequate and marginal N application rates, except for OL when inadequate and marginally adequate (80-90% maximum yield) concentrations were not different (P>0.05). Nitrogen application level affected (P<0.05) leaf potassium, phosphorus, calcium (Ca), magnesium (Mg) and sulfur concentrations. The largest effects were recorded for Ca and Mg where increasing N application level reduced leaf nutrient concentration. Petiole sap nitrate concentrations can be used as a rapid field test for distinguishing between a deficient and an adequate N supply. Where concentrations exceed critical values, they can be interpreted as such because N fertiliser toxicity rarely occurs under field conditions.

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...

Sap analysis for the prediction of stem yield and the need for extra nitrogen fertiliser for Kenaf

Abstract Kenaf (Hibiscus cannabinus var. Guatemala 4) was grown at Ayr in north Queensland under eleven nitrogen (N) treatments, including seven treatments with all nitrogen applied at planting and four split treatments in which half the nitrogen was applied at planting and half applied 67 days after planting. At weekly intervals from 36 days after planting, petioles from the youngest mature blades were sampled to investigate the possibility of using petiole sap analysis as a fertiliser‐management tool. The sap nitrate test showed promise in prognosing final stem dry‐matter yield. Relationships between final stem yield and sap NO3‐N at various sampling times, leading up to canopy closure of treatments supplied with 240 kg N/ha or more, are presented. Estimated desirable NO3‐N concentrations are also presented. Sap nitrate levels declined rapidly from 36 days after planting. The rate of decline of petiole nitrate levels depended upon the rate of nitrogen applied at planting. Monitoring sap nitrate over the...

Derivation of critical nutrient concentrations for growth rate from data from field experiments

Present methods for determining critical nutrient concentrations in plants and soils are unsatisfactory if concentrations change with time while the crop is growing. In such cases the critical concentration can only be applied in relation to growth rate at any given moment. For interpreting field experiments this introduces considerable difficulties: two possible approaches to these problems are suggested, one of which uses a simple simulation model. Results from a Brussels sprout nitrogen experiment are used to show how, using this approach, a single critical sap nitrate concentration (380 mg NO3 N.l−1 for 95% of potential growth rate) may serve to explain the results at all growth stages in three seasons.

Yields of Greenhouse Tomatoes Managed to Maintain Specific Petiole Sap Nitrate Levels

Abstract ‘Caruso’ tomatoes (Lycopersicon esculentum Mill.) were grown in peat-perlite-vermiculite in a greenhouse with five nitrate-nitrogen (NO3-N) fertilization concentrations in irrigation waters managed to maintain 200, 400, 600, 900, or 1200 µg NO3-N/ml in petiole sap as determined by weekly NO3-N quick tests. Nitrate-N fertilization concentrations immediately were increased 50% when petiole sap NO3-N levels first fell below these target levels; thereafter, NO3-N fertilization concentrations were increased only after petiole sap levels fell below target levels for 2 consecutive weeks. The critical target level of sap NO3-N was defined as the lowest petiole sap NO3-N target level producing maximum marketable fruit yields. Total fruit yields increased with increasing petiole sap NO3-N target levels through 1200 µg·ml–1. Marketable fruit yields were maximized at 3.2 kg/plant, with an estimated critical sap NO3-N target level of 1105 µg·ml–1. Application of the sap NO3-N management rules used in this experiment resulted in five adjustments in N fertilization concentrations over the 27-week crop cycle, with an average of 4.5 weeks between adjustments. This approach to the management of N fertilization based on the sap NO3-N level of the crop has potential to provide significant benefits in improved N use and crop productivity at a modest cost.

Diagnostic nitrogen concentrations for tomatoes grown in sand culture

The tomato cv. Flora-Dade was grown in sand culture with 4 nitrogen (N) levels of 1.07-32.14 mmol L-1 applied as nitrate each day in a complete nutrient solution. The youngest fully opened leaf (YFOL) and remaining (bulked) leaves were harvested at regular intervals over the 16-week growth period. Standard laboratory leaf total and nitrate N determinations were conducted in addition to rapid nitrate determinations on YFOL petiole sap. The relationships between plant growth and leaf N concentration, which were significantly affected by N application level, were used to derive diagnostic leaf N concentrations. Critical and adequate concentrations in petiole sap of nitrate-N, leaf nitrate-N and total N for the YFOL and bulked leaf N were determined from the relationship between growth rate relative to maximum at each sampling time and leaf N concentration. YFOL petiole sap nitrate-N concentration, which can be measured rapidly in the field by using commercial test strips, gave the most sensitive guide to plant N status. Critical values of 770-1 120 mg L-I were determined over the 10-week period after transplanting (first mature fruit). YFOL (leaf + petiole) total N concentration was the most consistent indicator of plant N status where critical values of4.45-4.90% were recorded over the 4- 12 week period after transplanting (early harvests at 12 weeks). This test was less sensitive but more precise than the petiole sap nitrate test. The concentrations of N, potassium, phosphorus, calcium and magnesium in YFOL and bulked leaf corresponding to the N treatments producing maximum growth rates are presented, because nutrient supply was close to optimum and the leaf nutrient concentrations can be considered as adequate levels.

Sampling Considerations for Nitrate Quick Tests of Greenhouse-grown Tomatoes

Abstract Tomato plants were grown in two greenhouse experiments to determine sampling guidelines for using semiquantitative quick tests of petiole sap nitrate to monitor crop N status. In Expt. 1, a 40-µg NO3-N/ml liquid feed rate produced maximum marketable yields of ‘Celebrity’ tomatoes (Lycopersicon esculentum Mill.) (3.4 kg/plant) with estimated petiole sap concentrations of 2138, 1091, and 636 µg NO3-N/ml at early bloom, small fruit, and full-ripe fruit stages, respectively. In Expt. 2, a stable minimum level of petiole sap NO3-N of about 800 µg·ml−1 was found during fruit production in maximally yielding (3.1 kg/plant) ‘Tropic’ tomato plants. These plants received 60 µg NO3− N/ml in liquid feed solutions during fruit production. Liquid NO3-N feed rates producing maximum yields in these experiments were about five times lower than those typically used for growing tomatoes. Sap nitrate content did not fluctuate greatly between 0803 hr and 1430 hr. Sap nitrate levels rose sharply in response to increased N feed concentrations and as a result of lower leaf pruning. Because of high day-to-day and plant-to-plant variation in petiole sap nitrate readings, strategies for obtaining results with sufficient diagnostic value would appear to involve at least weekly samplings of five to 15 plants, and restricting diagnoses of deficient crop N to instances where readings < 800 µg NO3-N/ml for two or more consecutive samplings have been obtained.

Nitrogen

During 1983–5, 46 trials were conducted on commercial vegetable crops in Eastern England to test the value of sap and soil nitrate tests for predicting N top‐dressing requirement. This paper summarises the results of the 20 brussels sprout trials. Optimum rates of top‐dressed N (Nopt) showed no simple relationship with sap or soil nitrate measured just before top‐dressing, nor with an index based on previous cropping, or the growers’ own practice. A multiple regression of Nopt on soil nitrate (0–60 cm) and an estimate of mineralization following top‐dressing accounted for 30% of the variance of Nopt. Consideration of average yield deficits resulting from various strategies shows that, from the point of view of growers’ profits, the safest approach is to apply a top‐dressing of 120 kg N. ha‐1 in all circumstances.

Nitrogen

Drip irrigated ‘Celebrity’ tomatoes were grown at 8 rates of nitrogen (N) on a well‐drained Oxisol on Central Oahu during summer 1985. Weekly fertigation was simulated by applying a small volume of solution containing nitrate N to the base of each plant each week. One thirteenth of the total amount of N was applied weekly. Petiole sap nitrate levels were monitored biweekly with paper test strips. Marketable yields of table‐ripe fruit over a 4‐week harvest period were related by a quadratic function to total N applied, with an estimated maximum yield of 35.1 t/ha occurring at a N application rate of 219 kg/ha. Sap nitrate‐N readings associated with 90 percent of maximum yield or more (desirable values‐DV) were 517–733 mg L‐1 at flowering, 478–915 mg L‐1 when the plants had small fruit, and 167–912 mg L‐1 when the plants had large green fruit. These DVs were somewhat lower than previously reported. Sap nitrate values that support maximum yields may be lower when N is supplied frequently than when...

Nitrogen

A rapid sap nitrate test for field use was evaluated for kiwi fruit. Good relationships were found between petiole sap nitrate concentration (SN) and total leaf nitrogen concentration (TN) in all trials, and between both SN and TN and shoot extension in young plants. Desirable values for optimum shoot growth were >800 ppm SN and >3.0% TN. Both SN and TN had a significant effect on fruit size, with small fruit being associated with low N levels. Desirable values for minimum percentage of undersize fruit were >2.9% TN and >400 ppm SN, sampled in December. There was a close relationship between SN (but not TN) at harvest and rate of fruit softening in all trials, with high SN levels associated with earlier softening. The desirable value for maximum fruit storage life was zero ppm SN at harvest.

The partitioning of nitrate assimilation between root and shoot of higher plants

Abstract The partitioning of nitrate assimilation between root and shoot of higher plant species is indicated by the relative proportions of total plant nitrate reductase activity (NRA) in the two plant parts and the relative concentrations of nitrate and reduced N in the xylem sap. These have been collated here from the literature and temperate and tropical species compared.Both the distribution of NRA and xylem sap nitrate: reduced N indicate that the following four generalizations can be made. Temperate, perennial species growing in low external nitrate concentrations (about 1 mol m−3) carry out most of their nitrate assimilation in the root. As external nitrate concentration increases (in the range found in agricultural soils, 1–20 mol m−3), shoot nitrate assimilation becomes increasingly important. Temperate, annual legume species growing in low external nitrate concentrations carry out most of their nitrate assimilation in the root. Shoot nitrate assimilation increases in importance as external nitrate concentration is increased. Temperate, annual non‐legume species vary greatly in their partitioning of nitrate assimilation between root and shoot when growing in low external nitrate concentrations. Regardless of the proportion carried out in the root at low external nitrate concentrations, nitrate assimilation in the shoot becomes increasingly important as external nitrate concentration is increased. Tropical and subtropical species, annual and perennial, carry out a substantial proportion of their nitrate assimilation in the shoot when growing in low external nitrate concentrations. The partitioning of nitrate assimilation between root and shoot remains constant as external nitrate concentration increases. It is proposed that a greater proportion of nitrate assimilation occurs in the shoot when an increase in the rate of nitrate uptake does not induce an increase in NR level in the root. Thus, a greater proportion of the nitrate taken up remains unassimilated and is passed into the xylem. A constant partitioning of nitrate assimilation between root and shoot is achieved by balancing NR levels in the root with rates of nitrate uptake.The advantages and disadvantages of assimilating nitrate in either the root or shoot are discussed in relation to temperate and tropical habitats.

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%.

Effect of nitrogen form on the growth and nitrate concentration of lettuce

A pot experiment with lettuce involving three N forms each at six application levels, showed that lettuce can be grown satisfactorily with a very low nitrate content when supplied with ammonium sulphate and a nitrification inhibitor. For plants growing on nitrate N, the optimum midrib sap nitrate concentration as maturity approached was about 1400 mg/1 NO3-N. Large losses of mineral N were observed from the peat medium, even in the absence of plants.