Petiole Nitrate Research Articles

Primary Non-Inversion Shallow Tillage Versus Moldboard Plowing Prior to Growing Potatoes: Short-Term Impacts on Potato Yield and Soil Properties in Eastern Canada

Potato (Solanum tuberosum L.) production often requires intensive tillage with the moldboard plow (MP), which involves deeper soil tillage and turning of the soil to provide enough loose soil for proper tuberization. Although tillage with the MP allows better potato seedbed preparation and lower weed pressure, it is also associated with increased soil compaction, soil aggregate destruction, and increased soil organic matter (SOM) mineralization. The objective of this four-year (2019–2022) study conducted in 14 commercial fields was to compare the use of MP with primary non-inversion shallow tillage (ST) in terms of their effect on selected soil health indicators, soil moisture, potato petiole nitrate concentration, potato yield, and specific gravity. Commercial fields ranged from 1.5 ha to 19 ha where the main field was split in half, with one side tilled using MP (22.5–30 cm plowing depth) and the other half using ST (15–30 cm plowing depth). Soil and plant tissue samples were taken within four sub-replicates (91 m2) created per each treatment per each site and three to four sites were used as replicates per each year. Compared to MP, ST increased active carbon by an average of 9%, soil respiration by an average of 26%, and aggregate stability by an average of 8%. Biological N availability (BNA) increased by an average of 20% with ST, and the effect was statistically significant in three out of four years. Soil moisture at 20 cm depth tended to be higher with MP than ST in three out of four years. Although not statistically significant, when averaged across four years, potato petiole nitrate concentrations were 5% and 12% higher with ST than MP in samples collected at the flowering and post-potato flowering stages, respectively. Total and marketable potato yields, along with specific gravity, were comparable for the two tillage regimes. Signs of soil improvement were observed at the early stages of ST adoption. Marketable yield was negatively correlated with the soil nitrate levels measured during the growing season but was positively correlated with active carbon, aggregate stability, and soil moisture. Future studies could compare both tillage regimes over multiple growing seasons to assess their impacts over a full cycle of rotation. The novelty of the present study was that it was conducted in real-life conditions across large growers’ fields with different conditions and across four years.

Benefits of controlled-release fertilizers for potato sustainable nitrogen management

The evaluation of potato response to controlled-release fertilizers (CRFs), as a sole source of nitrogen (N) or as a blend with a soluble N source, is essential to 1) develop the best management recommendations for using CRFs in potato production and 2) provide guidelines to CRF manufacturers for developing an optimal product. This study aimed to evaluate the potato yield and quality responses to N CRFs (polymer-coated urea [PCU]) vs soluble N sources. The experiments were conducted in major potato-growing regions in the United States and China. The current industry-recommended practice of 112 kg N/ha pre-plant soil broadcast of urea plus five in-season fertigations of 224 kg N/ha as urea ammonium nitrate (UAN-32) was compared to a single pre-plant application of 224 kg N/ha as a CRF as the sole source of N or as multiple blends of CRFs and soluble N sources (i.e., urea) at various ratios. The results demonstrated that petiole nitrate_N (NO3_N) levels and tuber yield with single pre-plant broadcast applications of 224 kg N/ha as CRF/urea blends (ratio of 25/75 or 50/50) were similar to those obtained with industry-standard N management practice. N uptake and yield were significantly greater with 220 kg/ha N as the CRF than those with the same N rate as urea. Unlike the current potato industry N practice, using CRFs as either a sole source of N or blended with urea reduces the total N rate and application frequency.

Evaluation of organic and mineral fertilizers on plant growth, minerals, and postharvest quality of celery (Apium graveolens L.)

Fertilizer type and rate may influence the quality of fruits and vegetables. This study compared plant growth, yield, minerals concentration, and postharvest quality of celery as affected by fertilizer type (organic and chemical) and nitrogen rate. Organic fertilizers were vermicompost (VER) and bio-organic fertilizer [compost plus Trichoderma harzianum (COM)]. Chemical fertilizers were urea (46% N) at high rate [322 kg·ha−1 N (UREA_HIGH)], optimal rate [196 kg·ha−1 N (UREA_OPT)], and low rate [138 kg·ha−1 N (UREA_LOW)]; ammonium nitrate [35% N (AN)] at 196 kg·ha−1 N, and an unfertilized treatment used as a control. Plants fertilized with UREA_HIGH had the highest plant height and yield. Yields with VER and COM were similar to those of UREA_OPT, UREA_LOW, and AN. Celery fed with organic fertilizers had reduced petiole nitrate accumulation and improved mineral content (N, P, and K). Organic fertilizer treatments were the most effective in maintaining celery quality (petiole color, weight loss, titratable acidity, pH, and total soluble solids). There was an enhancement of phytochemical compounds such as vitamin C, total phenols, and antioxidant activity in celery grown with organic fertilizers. Organic fertilizers released N more slowly into the soil, resulting in reduced plant growth and yields but increased celery's nutritional quality. Celery quality attributes with organic fertilizers were similar to those with the UREA_LOW treatment suggesting that the improved celery quality with the organic fertilizers may be attributed to reduced soil N.

Revising petiole nitrate sufficiency/deficiency guidelines for irrigated cotton in the Desert Southwest

AbstractPetiole nitrate‐nitrogen (NO3–N) sampling and testing remains a popular in‐season nitrogen (N) management practice in the western United States for cotton (Gossypium hirsutum L.). However, the present guidelines used by Arizona are greater than 35 yr old and are in need of updating. The objectives of this study were to relate in‐season petiole NO3 levels with lint yields and N deficiencies and to revise the former critical deficiency level guidelines by growth stage. Petioles were sampled between first square and peak bloom in nine site‐years of cotton N management field trials in Maricopa and Safford, AZ, from 2014 to 2018. Irrigation type in Maricopa was overhead sprinkler irrigation (OSI) (2014–2015) and subsurface drip irrigation (SDI) (2016–2018). In Safford (2014–2017), surface irrigation (SI) was used. Petiole NO3 in SDI was dramatically lower than with SI or OSI, mostly in the deficient range. Lower lint yields in zero‐N treatments compared with pre‐plant soil NO3 test–based reference treatments occurred in eight site‐years (Safford 2016 crop lost to late hailstorm) and were considered N deficient. Critical petiole NO3–N levels from 1984 were revised downward 1 g N kg−1 because several N‐fertilized treatment means of petiole NO3 were in that range and did not exhibit an N rate–related yield depression. Sampling cotton plants for petiole NO3 analysis should start within 1 wk of first bloom. Petiole NO3 dynamics and critical levels in SDI cotton required further study.

Hyperspectral imagery to monitor crop nutrient status within and across growing seasons

Imaging spectroscopy provides the opportunity to monitor nutrient status of vegetation. In crops, prior studies have generally been limited in scope, either to a small wavelength range (e.g., 400–1300 nm), a small number of crop cultivars, a single growth stage or single growing season. Methods that are not time- or site-specific are needed to use imaging spectroscopy for routine monitoring of crop status. Using data from four cultivars of potatoes (Solanum tuberosum L.), three growth stages and two growing seasons, we demonstrate the capacity of full-range (400–2350 nm) imaging spectroscopy to quantify nutrient status (petiole nitrate, whole leaf and vine total nitrogen) and predict tuber yield in potatoes across cultivars, growth stages and growing seasons. We specifically tested the capabilities of: (1) ordinary least-squares regression (OLSR) using traditional hyperspectral vegetation indices (VIs); (2) partial least-squares regression (PLSR) using full spectrum (400–2350 nm), VNIR- (visible-to-near infrared: 400–1300 nm) or SWIR-only (shortwave infrared: 1400–2350 nm) wavelengths; (3) predictive models developed for one potato type or planting season on withheld data from a different type or season. Our results show that OLSR models produced poor predictions with data from all dates pooled together (validation R2 < 0.01). Single-date OLSR models performed better (R2 = 0.20–0.60, relative RMSE = 15–30%). PLSR models performed well and were comparable using different spectral regions (full-spectrum, VNIR-only and SWIR-only), with validation R2 = 0.68–0.82 and RRMSE = 12–25%. Testing across potato types, models produced reliable predictions (R2 = 0.45–0.75, RRMSE = 13–30%), but with some bias. Cross-season models had validation R2 = 0.46–0.75 and RRMSE = 17–100%, with a more significant bias than the cross-potato type models. To achieve models that are generalizable and robust, we recommend: (1) obtaining ground measurements that capture the full range of plant growth conditions and developmental stages, and (2) ensuring that image processing approaches minimize spectral discrepancies among dates.

Cover crops prove effective at increasing soil nitrogen for organic potato production

Many farms in northeast California are experimenting with organic production to take advantage of price premiums and niche markets. A common challenge in organic farming is finding dependable nitrogen sources to meet the needs of vegetable and grass crops, especially in fields with low soil nitrogen. This study assessed the use of cover crops and organic amendments for increasing soil nitrogen for potato production at the Intermountain Research and Extension Center in Tulelake. Researchers evaluated several cover crop species, three planting dates and multiple cover crop mixes. Amendments included composts, manures, bloodmeal and soymeal. The data collected in the study included total nitrogen from cover crops and amendments, plant-available nitrogen in the soil, potato petiole nitrate and crop yield and quality. Vetches and field peas, managed as green manure, were successful at satisfying potatoes' in-season nitrogen demand. These cover crops, grown alone or in mixes with non-legume species, produced potato crops whose yield and quality were similar to crops grown with conventional fertilizers. The cover crops' influence on potato pest pressure was neutral. Chicken manure was the most cost-effective amendment for satisfying potatoes' in-season nitrogen demand.

Native grass ground covers provide multiple ecosystem services in Californian vineyards

Abstract Mechanisms responsible for the success or failure of agricultural diversification are often unknown. Most studies of arthropod pest management focus on enhancing natural enemy effectiveness. However, non‐crop plants can also change crop host quality by reducing or adding soil nutrients or water, and therefore improve or hamper pest suppression. Native perennial ground covers may provide food or habitat to natural enemies and, in terms of competition for soil nutrients or water, be more compatible with crop management than exotic annuals. We conducted a 3‐year vineyard study to examine the impacts of native perennial grasses on pests, natural enemies, crop plant condition and soil properties. We included three ground cover treatments: bare soil with a grower standard drip irrigation; native grasses with drip irrigation; and native grasses with drip irrigation as well as an additional flood irrigation to keep the grasses green and growing during the season. Numbers of leafhopper pests Erythroneura spp. decreased in both native grass treatments, where parasitism rates were higher. Vine petiole nitrate levels were lower in grass treatments, indicating competition for soil nitrogen, which is most often considered to be detrimental. Berry weight was higher in the irrigated treatment but did not differ between the bare soil and non‐irrigated grass treatment. Grape °Brix was similar in the bare soil and native grass treatments, suggesting native grasses did not compromise grape quality. In fact, leaf water stress was lower and soil moisture higher not only in the irrigated grass treatment but, at times, in the non‐irrigated grass treatment, compared with the bare soil treatment. Synthesis and applications. Our work shows that native grasses contribute to a reduction in vineyard leafhopper pests by reducing host quality through competition for soil nitrogen and providing food resources and/or habitat for natural enemies. Native grasses also improve soil water content and may be part of a water conservation program for perennial crops in dry climate regions.

Comparative Efficacy of White Mustard (Sinapis alba L.) and Soybean (Glycine max L. Merr.) Seed Meals as Bioherbicides in Organic Broccoli (Brassica oleracea Var. Botrytis) and Spinach (Spinacea oleracea) Production

White mustard and soybean seed meals were compared for weed control and yield of organically grown broccoli and spinach. The meals were incorporated into the soil 2 weeks before crop planting at two rates (1.24 and 4.48 t ha−1). Weed densities and hand-weeding time were recorded twice during the growing seasons and weed biomass was measured at crop harvest. Compared to the 1.24 t ha−1 soybean treatment, weed densities were 52 to 95% and 41 to 45% less at 3 and 6 weeks after planting, respectively, in both crops with the 4.48 t ha−1 white mustard seed meal treatment. Time required for hand weeding at these times was also reduced by up to 82% and 48%, respectively. Broccoli yield was similar in all the treatments, but spinach yield was greatest in the 4.48 t ha−1 treatments for both seed meals. Petiole nitrate and nutrient concentrations in both crops were generally similar in all the treatments.

Efficacy and Cost of Cultivators, Steam, or an Organic Herbicide for Weed Control in Organic Vineyards in the San Joaquin Valley of California

Weed management is an important problem faced by organic grape (Vitis vinifera) growers as there are few effective and economic options available. However, new organically acceptable weed control products have become available in recent years. Several studies were conducted to compare the efficacy of two mechanical weed control methods (French plow and Bezzerides tree and vine cultivator) with steam, and an organic herbicide (d-limonene) in organic raisin and wine grape vineyards. The experiments were designed as split plots with the aforementioned treatments as main plots with additional weed control treatments (handhoeing and no handhoeing in the raisin grape vineyards; hoeing, no hoeing, steam, and d-limonene in the wine grape vineyard) one month after the main plot treatment as subplots. The plow provided the greatest level of weed control among the treatments followed by the cultivator. The time required to hoe mechanically cultivated plots was also generally lower than the other treatments. Steam and herbicide only suppressed weeds for 2–3 weeks, and the time needed to hoe plots in these treatments was generally similar to the untreated control at all sampling dates. The mechanical treatments also were two to four times more cost-effective than steam or herbicide. Therefore, mechanical treatments were the most effective and economical weed control methods, though none of the treatments affected vine growth, midday stem water potential, petiole nitrate concentration at bloom, grape yield, or quality.

Measurement of Nitrate Efflux from Roots and Its Relation to Nitrate Accumulation in Two Oilseed Rape Cultivars

Studies have reported significant differences in nitrate accumulation among genotypes within a crop species, but the reason for these differences is not clear. This study investigated nitrate (NO3) efflux from roots of two oilseed rape cultivars (Brassica napus L. cvs. ZY821 and D89) and the relationship between nitrate efflux and plant nitrate accumulation. Nitrate efflux was estimated by measuring nitrate released from roots into nitrate-free nutrient solutions 58 days after sowing. The solutions were buffered with either 2.0 mM (n-morpholino) ethanesulfonic acid (MES) or 0.05 mM phosphate. Whole-plant and petiole nitrate accumulations were significantly greater for ZY821 compared to D89. Nitrate efflux varied diurnally, and the difference between cultivars was greater in the morning than in the afternoon. Data suggested that the relatively high pH of the phosphate-buffered solutions increased nitrate efflux rates from oilseed rape plants; therefore phosphate buffer should not be used when making direct determinations of nitrate efflux. Maximum cumulative nitrate efflux was 0.97 μmol g−1 fresh-weight (FW) root for ZY821 and 1.9 μmol g−1 FW root for D89. Maximum nitrate efflux rate was 0.084 μmol g−1 FW min−1 for ZY821 and 0.097 μmol g−1 FW min−1 for D89. These results indicated that between the two cultivars, ZY821 had the greatest petiole nitrate nitrogen concentration and the lowest total nitrate efflux. We suggest that cultivars with low nitrate efflux rates are able to translocate and store greater amounts of nitrate in aboveground plant organs, especially in petioles.

Nitrate and potassium concentrations in cotton petiole extracts as influenced by nitrogen fertilization, sampling date and cultivar

The effect of nitrogen fertilization levels on seed cotton yield responses of cultivars from Andalusia was studied during two consecutive years. To obtain preliminary information for improving nutrient management, the analysis of nitrate and potassium (K) was performed in petiole extracts at critical times (flowering, boll-setting, boll growth) during the growth cycle. Signif icant differences among cotton cultivars were found for petiole nitrate and K concentrations. The highest petiole nitrate and K concentrations were found in cultivar "Crema 111" with 4.140 and 14.180 mg/kg respectively. These concentrations were affected by N treatment and sampling date. The relationships among petiole nutrient concentrations and seed cotton yield depended on sampling date, cultivar and year. The highest association between petiole nitrate and yield was found early in the season in 2003 (r = 0.918 and r = 0.965 for "Crema 111" and "Sor Angela" respectively). The analysis of petiole extracts for controlling plant nutritional status and optimize seed cotton yield requires a systematic assessment as critical values in nutrient concentration for seed cotton yield may differ depending on cultivar, soil type, sampling date and crop management. The technique of petiole analysis used in this paper might be useful for detecting genotypes with improved nutrient uptake or use efficiency.

Detection of Nitrogen Sufficiency in Potato Plants Using Gene Expression Markers

In-season chemical or optical measures of crop N status can be effective tools in optimizing potato fertilizer N management. The feasibility of using a gene expression as an alternative approach for early detection of potato nitrate deficiency was examined using three potato cultivars (Shepody, Russet Norkotah, and Red Pontiac) with abundant (7.5 mM NO3), limited (0.75 mM NO3) or deficient (0 mM NO3) nitrate supply in nutrient culture over a 7 d period. RNA was extracted from the last fully expanded leaf and quantified using realtime RT-qPCR. Reduced nitrate supply had no measurable effect on shoot dry weight or leaf chlorophyll concentration, but decreased petiole nitrate concentration. Under deficit nitrate supply, down-regulation of nitrate reductase and nitrite reductase was measured within 3 days for all cultivars, and down-regulation of asparagine synthetase was measured in two cultivars. Nitrate supply had no effect on expression of ammonium transporter. In this experimental system, plant gene expression markers detected a reduction of nitrate supply prior to measureable reductions in plant growth or in N status measured using common chemical or optical methods.

Indicators of Cotton Nitrogen Status

ABSTRACT Nitrogen (N) deficiency limits cotton yields, while too much N causes excessive vegetative growth hurting yields, wastes expensive inputs, and causes environmental pollution. Diagnostic indicators are needed to assess cotton N status so that yields can be optimized as efficiently as possible. This study evaluated selected tools for predicting cotton responses to N fertilizer application. Petiole nitrate (NO3)-N (PNN) concentration was found to correlate with cotton N status and a good indicator of potential for response to N application. Critical PNN concentrations for irrigated cotton in subtropical South Texas at first bloom, and 10, 20 and 30 d later were determined to be 15.0, 9.0, 4.5, and 2.0 g kg− 1, respectively. These critical PNN levels are higher than in more humid areas of the traditional southern US Cotton Belt, probably due to the effects of the subtropical climate. Cotton plants in this area tend to be less vegetative, possibly due to shorter growing season day lengths, and therefore need to be “pushed” slightly harder with greater N fertilization. Leaf total N concentrations were found to be less responsive to changes in applied N than were PNN levels. Although leaf N tended to be more stable over time, there was no consistent pattern between years. Leaf N values of 35 g kg− 1 or less appear to represent a deficiency at any time, and optimum levels may be slightly higher. Nodes above white flower showed very small responses to N fertilization and the differences occurred late in the bloom period. Chlorophyll meter readings showed a good relationship with N fertilizer application within a given sampling date, but much greater variability occurred between dates and due to other factors. The most effective indicator of cotton N status was found to be PNN, and to a lesser extent leaf N, but none of other parameters could be recommended for purposes of making inferences as to N status of cotton.

Effects of Various Preplant and In‐Season Nitrogen Management Practices for Potatoes on Plant and Soil Nitrogen Status

Adequate availability of nitrogen (N) to satisfy potato crop N requirement is critical for production of optimal tuber yields with high processing qualities, which will contribute to maximum net returns. The agroclimatic conditions in the Columbia Basin region in the Pacific Northwest (PNW) supports high potato tuber yields with high processing qualities. Best management of N fertilization is important to increase N uptake efficiency and to minimize N losses. Monitoring soil and petiole N provides a basis to evaluate available N in the soil and N status in the plants. This study was conducted on a Quincy fine sand (mixed, mesic Xeric Torripsamments; >95% sand) using ‘Ranger Russet’ potato cultivar. Potato followed by 2 years of sweet corn rotation was adapted in this study. Treatments included the following preplant (PP) + in‐season (IS) N rates in kg ha−1: (i) 56 + 280, (ii) 112 + 224, or (iii) 112 + 336 in 2004 or 112 + 112 in 2005. The IS N was applied in five equally divided doses at 2‐week intervals, 3 weeks after seedling emergence. An additional treatment was included with treatment (ii) N rates, except that IS N was delivered in 10 weekly applications. Total tuber yield ranged from 54 to 64 and 78 to 90 Mg ha−1, respectively, in 2004 and 2005. In 2004, during the first 65 days after emergence (DAE), petiole nitrate (NO3) concentration was lower in the treatment (i) than that in the other treatments. This difference was not evident in 2005. The petiole NO3 concentrations were lower in 2005 than that in 2004, particularly during latter part of the growing period. Soil available N [nitrate NO3‐N + ammonium (NH4) N in the top 30 cm] concentrations were also greater in 2004 than those in 2005. Soil N appeared to increase toward the end of the growing season in 2004, which has negative effects on tuber yield and quality. Across all treatments, total tuber yield and that of >340‐g grade tubers were greater in 2005 than that in 2004.

Effect of Straw and Fertilizer Nitrogen Management for Spring Barley on Soil Nitrogen Supply to a Subsequent Potato Crop

The effect of straw management (straw removed or retained) and fertilizer N rate (0, 80 or 160 kg N ha-1) on a preceding barley rotation crop on N availability to the subsequent potato crop was evaluated in two years. Nitrogen fertilizer application increased barley grain and straw yield and N uptake, and generally decreased straw C:N ratio. Barley N rate increased residual soil nitrate at harvest in one year, but not in the subsequent spring. Barley management had no effect on assays of soil N supply or on total tuber yield, tuber specific gravity, plant dry matter accumulation or petiole nitrate concentration for an unfertilized potato crop. However, straw retention reduced potato plant N accumulation in both years, and reduced soil nitrate content in vegetation-free plots in one year, compared with straw removal. In this cool, humid environment, management of a barley rotation crop has limited short-term effects on N supply to a subsequent potato crop.

Efeito da adubação azotada, fosfatada e potássica na cultura da batata.: Produtividade e eficiência de uso dos nutrientes

Results from fertilisation field trials with nitrogen, phosphorus and potassium on potato crop are presented. The study was carried out in Sta Apolonia farm, NE Portugal, in 2002. Three independent experiments, one for each nutrient, were organized in completely randomized designs. Phosphorus treatments included 0, 50, 100 and 200 kg P2O5/ha. Potassium treatments were 0, 50, 100, 200 kg K2O/ha and N treatments 0, 50, 100, 200 and 400 kg N/ha. Calcium superphosphate (18 % P2O5), potassium chloride (60 % K2O) and urea (45 % N), in rates according to the above-mentioned treatments, were broadcast and incorporated in their respective plots with pre-planting tillage. The higher tuber yield recorded for all treatments reached 42 Mg/ha. Phosphorus rate did not significantly (a < 0,05) influence tuber yield, while with potassium and nitrogen fertilisation a significant increase of 8 Mg/ha above the control was recorded. Exponential asymptotic equations were used to fit the crop response to applied K and N. The response curves show an initial increase on tuber yield, followed by a progressive attenuation as the nutrient rate increase and stabilising in an extended plateau for the higher nutrient rates. None of the elements influenced the size and the dry matter percentage of the tubers. Petiole nitrate concentrations and chlorophyll SPAD readings, performed with the portable tools: RQflex reflectometer and SPAD-502 chlorophyll meter, showed correspondence with fertiliser-N treatments. Thus, they can be used to diagnose the N nutritional status of crop. The N, P and K use efficiency was very low, stressing the importance of sowing catch crops in the fall, following the harvest of the potato, in order to minimize environmental impacts mainly associated with residual N.

Assessing organic potato cropping systems at the end of the first cycle of four-year rotations using principal component analysis

A single or a few variables may not be sufficient to evaluate management practice effects in a complicated cropping system, so six plant and 13 soil variables were integrated using principal component analysis (PCA) to examine nine 4-yr organic potato rotations. The rotations were combinations of three forage levels (0, 1, and 2 yr of forages) with three soil amendments (monogastric compost, ruminant compost, and alfalfa meal). Quantities of amendments were estimated by soil test recommendations and amendment nutrient availabilities. In the 4th potato year, one half of each original plot was not amended ("the 4th year unamended plots"), while the other half received soil amendments ("4th year amended plots"). The first three principal components explained 67 and 63% of the overall variation for the 4th-yr amended and unamended plots, respectively. PCA ordination plots indicated that, overall, the type of soil amendments had larger effects on soil and plant variables, but forage frequencies were influential for the amendments showing weaker effects. PCA loading plots indicated that plant nutrient uptake and potato total tuber weight would be the best single variables for characterizing the current cropping systems. Plant variables, except for potato petiole nitrate, were closely displayed, but they were not strongly correlated with soil variables, which may reflect the high background fertility of this site. Applications of soil amendments in the 4th yr affected the relationships among variables, most notably the strength of relationships between soil pH and soil N variables. The results suggest that PCA provides an effective way to compare complex cropping systems, especially in situations with high site heterogeneity. Key words: Principal component analysis, soil amendment, livestock system, forage, potato, organic crop rotation

Nitrate transporters and peptide transporters

In higher plants, two types of nitrate transporters, NRT1 and NRT2, have been identified. In Arabidopsis, there are 53 NRT1 genes and 7 NRT2 genes. NRT2 are high-affinity nitrate transporters, while most members of the NRT1 family are low-affinity nitrate transporters. The exception is CHL1 (AtNRT1.1), which is a dual-affinity nitrate transporter, its mode of action being switched by phosphorylation and dephosphorylation of threonine 101. Two of the NRT1 genes, CHL1 and AtNRT1.2, and two of the NRT2 genes, AtNRT2.1 and AtNRT2.2, are known to be involved in nitrate uptake. In addition, AtNRT1.4 is required for petiole nitrate storage. On the other hand, some members of the NRT1 family are dipeptide transporters, called PTRs, which transport a broad spectrum of di/tripeptides. In barley, HvPTR1, expressed in the plasma membrane of scutellar epithelial cells, is involved in mobilizing peptides, produced by hydrolysis of endosperm storage protein, to the developing embryo. In higher plants, there is another family of peptide transporters, called oligopeptide transporters (OPTs), which transport tetra/pentapeptides. In addition, some OPTs transport GSH, GSSH, GSH conjugates, phytochelatins, and metals.

Nitrogen Utilization, Yield, Quality and Soil Properties In a Sugarbeet Crop Amended With Municipal Solid Waste Compost

The aim of this research was to study different ways of nitrogen (N) fertilization and soil tillage management to ensure high yield, quality and correct usage of the available resources. Therefore, a two-year field experiment (2001 and 2003) was carried out on a sugarbeet crop grown in a Mediterranean environment to evaluate the effects of two soil tillage depths (10-15 and 40-45 cm) and of a municipal solid waste (MSW) compost application, compared to mineral N fertilization. The following fertilization treatments were compared: MSW compost at 100 kg N ha−1 (Ncom); mineral N fertilizer at 50 kg ha−1 (N50) and at 100 kg ha−1 (N100); MSW compost combined with mineral N fertilizer (Nmix) (50 kg ha−1 as organic N plus 50 kg ha−1 as mineral N); slow release organic-mineral fertilizer (Nslow) and an unfertilized control (Contr). In each trial year, growth parameters, plant and soil N indicators, yield, quality, N uptake and N efficiency, soil chemical characteristics and N mineral deficit in the soil were determined. The findings of this research highlighted that MSW compost was an important N source for sugarbeet, especially when MSW compost was combined with mineral N fertilizer. In fact, the Nmix treatment did not determine any significant reduction in root (32.5 vs. 36.4 t ha−1 of N100) and sucrose yields (3.56 and 3.65 ha−1). Furthermore, it presented a significantly lower amount of one of the most important qualitative parameters, the alfa amino N (1.74 and 1.97 meq 100 g−1 of N100), and ensured the least soil N deficit in 2003. The application of MSW compost significantly increased the extracted organic carbon in both 2001 (37% of increase for compost treatment in respect to unfertilized control) and 2003 (24%). Higher values were also recorded for total organic carbon in 2001 (20% of increase) and for humified organic carbon in 2001 (27%) and in 2003 (16%), whereas its application did not increase the total content of heavy metals. Finally, among plants and soil N indicators tested, the petiole nitrate content was the only one significantly and positively correlated with root and sucrose yields, indicating that it was an effective tool to monitor N supply.

Petiole and Soil Nitrogen Concentrations during the Growing Season of Two Potato Cultivars as Influenced by Different Nitrogen‐Management Practices

Fine‐tuning potato nitrogen (N) management for irrigated sandy soils is a desirable goal to optimize the production and minimize negative impacts on the environment. Effects of different rates of preplant N (PP‐N) applications and different rates and frequencies of in‐season N (IS‐N) for two potato cultivars were evaluated for 2 years (2001 and 2002) in a Quincy fine sand (mixed, mesic, Xeric Torripsamments) in the Pacific Northwest (PNW). In the 2001 experiment, the petiole nitrate (NO3‐N) concentrations in both the cultivars were in the optimum range in the samples taken 22 days after emergence (DAE). In the subsequent sampling, the petiole NO3‐N concentrations showed a wide range proportional to the rates of IS‐N. In the 2002 experiment, the petiole NO3‐N concentrations were in the excess range in most treatments until about 51 DAE in both the cultivars, followed by a decline in concentrations to the low range. The petiole phosphorus (P) and potassium (K) concentrations were mostly above the excess range in both the cultivars over the entire sampling period. The soil N data showed that the transformation of urea N was quite rapid and that the extractable ammonium (NH4‐N) and NO3‐N concentrations in the soil returned to the background levels within 90 days after the PP‐N application. The results of this study demonstrate a rapid transformation of preplant applied urea N into NH4‐N and NO3‐N and depletion of the available N in the top 120 cm of soil. This, in turn, supports the need for IS‐N applications to meet the crop N requirement during the later growing period.