Soil nitrate-N Concentrations Research Articles

Effect of Poultry Compost on Productivity and Quality of Beets

One characteristic of compost that might provide greater incentive for use by vegetable growers is suppression of soil-borne diseases in crops grown on compost-amended soils. The mode of action of low rates of compost on vegetable growth may include stimulation of microbial activity for suppression of soil-borne diseases, enhanced plant resistance, and improved nutrient availability. Preliminary research on beets demonstrated that higher stands and decreased loss to root rot diseases in poultry compost-amended plots contributed to marketable yields which were twice that of the control plots. This presentation will summarize research results from studies to determine if compost reduced disease severity by changing in soil microbial activity or if these products primarily improved plant growth as a result of increased nutrient availability. Three field experiments explored impact of two commercially available poultry compost products (2 to 5 T/A) and two rates of chemical fertilizer, on growth and disease incidence on beets. Soil microbial activity was estimated using an enzyme assay, and soil nitrate-N and ammonium-N concentrations were also measured, three times over the season. Results indicated that these composts act primarily through a nutrient affect to enhance beet yield. Neither compost affected microbial activity in the top 8 inches of soil. Both products had significant, opposite effects on available soil nitrogen. One product significantly increased the amount of available soil nitrogen over the season and beet yields. The different methods of production of the two poultry composts tested in this research had significant implications for potential use in either greenhouse or field systems. The effects of these composts on crop fertility and composition will be discussed.

Cover Crop Response to Late-Season Planting and Nitrogen Application

Cover crops aid in reducing precipitation runoff, soil erosion, and N losses in highly sloped, mountainous regions. Corn (Zea mays L.) producers in states with late spring warmup and early winters have limited success when planting cover crops following harvest. Studies were conducted from 1992 through 1995 in southern and northern West Virginia to evaluate the groundcover ability of several late-planted cover crops and their dry weight response to fall N application. In most years, vetch (Vicia villosa Roth cv. Common) and Austrian winter pea (Pisum sativum var. arvense L. Poir cv. Austrian winter) produced the least groundcover and dry matter of all species evaluated. Rye (Secale cereale L. 'Abruzzi' and 'Wheeler') was the most reliable and winter-hardy cover crop, regardless of location. Initial soil nitrate-N concentrations at planting averaged 12 ppm in soils with continuous corn-production and no history of manure application (southern experiment) and 40 ppm in soils with similar rotation and a history of manure application (northern experiment). Nitrogen application did not consistently increase the likelihood of cover crop survival, but increased dry matter for some cover crops on soils with low initial N levels. At the southern location, Abruzzi rye planted alone and common rye in combination with common vetch responded positively to additional N application in 3 out of 3 and 2 out of 3 yr, respectively. 'Pastar' rye (1992-1993), common rye (1993-1994), wheat (Triticum aestivum L.) (1994-1995), and barley (Hordeum vulgare L. 'Barsoy') (1994-1995) also responded positively to N application at the southern location. Cover crops did not respond to additional N application at the northern location on soils high in initial N fertility. Corn producers in mountainous, highly sloped land should consider methods for planting cover crops earlier to ensure plant survival and to protect soil during the winter.

Denitrification with and without maize plants (Zea mays L.) under irrigated field conditions

The study was conducted under irrigated field conditions to examine the effect of maize plants on denitrification. Both planted and unplanted field plots received 150kgNha–1 as urea. In a third treatment, which was also planted and received urea at 150kgNha–1, the soil nitrate N content was brought up to equal to that in the unplanted plots by applying additional doses of N as calcium nitrate. Soil cores were collected 24 and 72h after irrigation and the denitrification rate was measured by the acetylene inhibition method. Nitrate-N content, aerobically mineralizable C, microbial biomass carrying capacity and denitrification potential were also studied on field-moist soil. Maize plants grown under field conditions always had the potential to increase denitrification in conditions of both high and low water-filled porosity. When nitrate-N content of the planted soil decreased due to plant uptake, denitrification was reduced in the planted soils. However, when nitrate-N uptake by plants was compensated through additional doses of nitrate fertilizer, denitrification was always higher in planted than unplanted soil. The stimulatory effect of plants on denitrification was observed at both high and low soil nitrate-N concentrations, though it was more pronounced at high nitrate-N levels. The effect of plants on denitrification and related parameters was confined to the root zone.

Cardamom, mandarin and nitrogen-fixing trees in agroforestry systems in India's Himalayan region. II. Soil nutrient dynamics

A study on seasonal soil nutrient dynamics was made in large cardamom (Amonum subulatum) and mandarin (Citrus reticulata) agroforestry systems in the Sikkim Himalaya, India. Alnus nepalensis was the N2-fixing associate in the large cardamom system, and Albizia stipulata in the mandarin agroforestry system. Sites without N2-fixing species in both agroforestry types comprised native non-symbiotic mixed tree species. Soil was acidic in the cardamom agroforestry and slightly acidic to neutral in the mandarin agroforestry system. Total-N in soils was the highest in the forest-cardamom stand and the lowest in the mandarin-based agroforestry systems. Soil ammonium-N and nitrate-N concentrations were highly seasonal, and the ratio of seasonal maximum and minimum varied up to six times. The C/N ratio was higher in cardamom agroforestry indicating lower N availability than in the mandarin agroforestry. Cardamom stand with Alnus showed a relatively narrower C/N ratio. N2-fixing species help in maintenance of soil organic matter levels with higher N-mineralization rate as land use change from natural-forest system to agroforestry systems with sparse tree populations. Ratios of inorganic-P/total-P were lower in cardamom agroforestry than the mandarin agroforestry. Seasonal fluctuation in Ca-PO4, Al-PO4 and Fe-PO4 contents regulated the availability of phosphates to some extent for plant uptake.

Fertilization Rate and Growth of `Hamlin' Orange Trees Related to Preplant Leaf Nitrogen Levels in the Nursery

Our objectives were to determine if leaf N concentration in citrus nursery trees affected subsequent growth responses to fertilization for the first 2 years after planting and how N fertilizer rate affected soil nitrate-N concentration. `Hamlin' orange [Citrus sinensis (L.) Osb.] trees on `Swingle' citrumelo rootstock [C. paradisi Macf. × P. trifoliata (L.) Raf.] were purchased from commercial nurseries and grown in the greenhouse at differing N rates. Three to five months later trees were separated into three groups (low, medium, high) based on leaf N concentration and planted in the field in Oct. 1992 (Expt. 1) or Apr. 1993 (Expt. 2). Trees were fertilized with granular material (8N–2.6P–6.6K) with N at 0 to 0.34 kg/tree yearly. Soil nitrate-N levels were also determined in Expt. 2. Preplant leaf N concentration in the nursery varied from 1.4% to 4.1% but had no effect on trunk diameter, height, shoot growth, and number or dry weight in year 1 (Expt. 1) or years 1 and 2 (Expt. 2) in the field. Similarly, N fertilizer rate had no effect on growth during year 1 in the field. However, trunk diameter increased with increasing N rate in year 2 and reached a maximum with N at 0.17 kg/tree yearly. Shoot number during the second growth flush in year 2 was much lower for nonfertilized vs. fertilized trees. Leaf N concentrations increased during the season for trees with initially low levels even for trees receiving low fertilizer rates. Soil nitrate-N levels were highest at the 0.34-kg rate, and lowest at the 0.11-kg rate. Nitrate-N levels decreased rapidly in the root zone within 2 to 3 weeks of fertilizing.

Preplant Manure on Alfalfa: Residual Effects on Corn Yield and Soil Nitrate

Overapplication of N from various sources can be partially attributed to the lack of proper N crediting when organic N sources, such as alfalfa (Medicago sativa L.) and manure, are part of a farm's cropping system. The objectives of this study were to evaluate: (i) the effect of manure applied prior to alfalfa establishment on subsequent corn (Zea mays L.) grain yield and soil nitrate-N concentrations; and (ii) grain yield response to alfalfa cutting management preceeding plowdown. Prior to alfalfa establishment, three preplant manure rates (3 000, 6 000, and 12 000 gal/acre) were applied at Rosemount MN, on a Waukegan silt loam (fine-silty over sandy or sandy-skeletal, mixed, mesic Typic Hapludolls) and at Waseca MN, on a Nicollet clay loam (fine-loamy, mixed, mesic Aquic Hapludolls). Fall alfalfa cutting management treatments consisted of either leaving or removing the fourth-cutting herbage before plowdown. First-year corn grain yields following alfalfa plowdown were similar for all manure treatments applied prior to alfalfa establishment. By the second and third year after alfalfa, corn yields declined and yield responses to the original manure treatments were less than those observed with 30 lb/acre of fertilizer N. Not harvesting the fourth-cutting herbage before mold board plowing significantly increased yields by an average of 4.2 bu/acre. In the first year after alfalfa plowdown, the N contribution of the alfalfa, whose N credit can be estimated by the in-season nitrate-N test, overshadowed the contribution of the manure, which can be partially estimated by the preplant residual N test or by the in-season nitrate-N test, in the first year after plowdown. By the third year of corn following alfalfa, the manure-N and alfalfa-N contributions to the mineralizable N pool are exhausted based on soil nitrate-N concentrations and corn grain yield response. Good stands of alfalfa can supply optimal N for corn in the year after plowing, regardless of whether preplant manure was applied prior to alfalfa seeding.

A deterministic evaluation analysis applied to an integrated soil-crop model

The WAVE-model (Water and Agrochemicals in the soil and Vadose Environment), simulating one-dimensional transport of water, solute and heat in the unsaturated zone, was used to simulate the behaviour of water and nitrogen in soils cropped with winter wheat and sugar beet. Soil water transport was modelled using the Richards equation, while solute transport was described with a convection equation. Soil mineral nitrogen transformations were simulated using first-order kinetics, while for the organic matter turnover three organic matter pools were considered. A summary model was used to simulate crop growth. The performance of the integrated model was evaluated in a deterministic way using field data for a three-year period. The data of the first year were used for the model calibration. The remaining set of data was used to evaluate the capacity of the model to predict soil water content, the soil nitrate-N content, the soil ammonia-N content, the soil temperature, the soil water pressure head, the leaf area development and the dry matter accumulation in different plant organs. A screening sensitivity analysis indicated that the calculated nitrogen balance was sensitive to the soil hydraulic properties and the crop K c-factors for the given scenario. The effect of uncertainty of the sensitive hydraulic properties on the calculated nitrogen balance was investigated using Monte Carlo simulation. Taken into consideration the variability on the soil hydraulic parameters, predicted nitrate-N flux out of the soil profile at a depth of one meter ranged for the simulated period (three years) between −10 and +10 kg ha −1.

Spring Wheat and Barley Response to Long-Term Fallow Management

Crop rotations with a high frequency of fallow remain the dominant cropping practice in the semiarid northern Great Plains. Tillage to control weeds during fallow periods increases soil exposure to erosion by wind. A fallow management study, initiated on a clay loam soil in 1955, has been used to compare tillage alone, herbicides alone, and combinations of tillage and herbicides on the yield and quality of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). From 1977 to 1991, average spring wheat and barley yields were similar regardless of tallow treatment, with a 3.1 bu/acre difference between highest (31.4 bu/acre) and lowest yielding (18.3 bu/acre) treatments for wheat, and a 4.1 bu/acre difference for barley (54.4-58.5 bu/acre). Fallow with summer herbicides and cultivation with wide blade in fall resulted in the highest grain and grain N yields for wheat and barley, and highest soil nitrate-N concentration. The use of herbicides alone resulted in the highest level of crop residue conservation and plant-available water (PAW) at seeding. When tillage was used alone, only the wide blade cultivator maintained sufficient crop residue cover to protect against wind erosion. Grain yields on fallow increased with precipitation in May and June, the period of tiller formation and stem elongation, and decreased with increasing evaporative demand in June and July, during grain filling. Environmental conditions prevailing from May to July explained 67 % of the yield variability observed in spring wheat and 83 % in barley. Producers using a cereal-fallow rotation are encouraged to explore herbicide-tillage combinations for fallow as a means of ensuring erosion protection and optimizing grain yield potential

Tillage effect on seasonal nitrogen availability in corn supplied with legume green manures

It has been shown that legume green manures have great potential for replacing a substantial amount of the N fertilizer required for corn (Zea mays L.) production. An experiment was conducted in central Pennsylvania (USA) to study seasonal fluctuation of nitrogen (N) availability in corn with conventional tillage (CT) and no-till (NT) following red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth) green manures double-cropped with winter wheat (Triticum aestivum L.). Samples of corn, weeds, and soil were taken periodically and analyzed for total N content in plant tissue and soil nitrate-N content. The sum of plant N (corn plus weed) and soil nitrate-N in the upper 45 cm profile was used as an indicator of total available N. Under CT, total available N increased rapidly upon legume incorporation and reached 80% of the maximum within 4 weeks. Under NT, total available N increased steadily after the legumes were killed with herbicides and reached a maximum within 7 to 8 weeks. Seasonal corn N accumulations with the legume N source were similar to those where corn followed fallow with 200 kg N ha−1 fertilizer with CT, but were less than those in the same fallow 200 kg N ha−1 treatment with no-till. Dry weather conditions together with weed competition reduced N availability to the no-till corn compared to the CT treatments. The seasonal fluctuations of total available N and corn N uptake suggest good synchronization between N availability from the legume green manures and N accumulation by corn plants in both tillage systems under the conditions of this study.

111 EFFECTS OF N SOURCE, APPLICATION FREQUENCY, AND SOIL NITRATE CONCENTRATION ON PEPPER YIELD AND QUALITY

Various applications of N fertilizer formulations to bell pepper plots were made to affect soil nitrate-N concentrations from 5 to 30 ppm throughout the growing season. Number and weight of marketable grades for the 1st and 3rd harvests were improved by increasing soil N from 5 to 30 ppm. In the final (4th) harvest, marketable yield was highest for applications maintaining soil N of 25 ppm. Earliness was enhanced by N sources with Ca(NO3)2 producing the earliest yield followed by NaNO3 and NH4NO3. Total marketable yield produced by Ca(NO3)2 or NaKNO3 was 3 t/ha higher than by NH4NO3 applications. High marketable quality was maintained with Ca(NO3)2 and NaNO3 treatments. The highest blossom-end rot (BER) incidence was associated with NH4NO3 applications. But the N source effect on BER was strongly influenced by soil nitrate levels. At 10-20 ppm soil N, leaf Ca decreased during the 8 to 12 week period, but at higher soil N, leaf Ca remained unchanged, indicating a constant Ca uptake during the critical growth period.

Nitrogen Fertilizer Effects on Soybean Growth, Yield, and Seed Composition

While previous research has been contradictory, potential grain yield responses and seed protein increases have led to continuing interest in N fertilizer application to soybean (Glycine max (L.) Merr.]. Field experiments were conducted at seven locations from 1990 to 1991 in Alabama to determine soybean response to N fertilization at vinous growth stages. Treatments included a factorial arrangement of soybean cultivar ('Stonewall' or 'Sharkey') and N rate/timing treatments in a split plot design. Nitrogen rate/timing treatments were: (i) no N, (ii) 30 Ib N/acre at planting, (iii) 50 Ib N/acre at first bloom (R1), and (iv) 50 Ib N/acre at early pod fill (R5). Plant samples were collected at R1 and R5 for dry matter yield and N determination. Grain yields were determined and grain samples were collected at harvest for protein and oil analyses [...]

Effects of stubble and N fertilization management on N availability and uptake under successive rice (Oryza sativa L.) crops

Experiments were conducted in fields which had a history of nil to four rice (Oryza sativa L.) crops during the previous four summers. Incorporating stubble after each harvest reduced soil nitrate-N content between crops, but increased soil N mineralization potential. During the fourth successive crop, plots where stubble had been incorporated after the previous three harvests had an average 21% more soil NH4N and 22% more N uptake than plots where stubble had been burnt.

CONCENTRATION CRITIQUE DES NITRATES DANS LES FEUILLES EN RAPPORT AVEC LE RENDEMENT ET LES RESIDUS DANS UNE CULTURE DE CHOUX

The objectives of this work were to determine the nitrate-N concentrations related to maximum ball cabbage (Brassica oleracea var capitata L.) yield and corresponding to the lowest soil nitrate level. Accordingly, field trials were carried out comparing four rates of N, P and K fertilization at six sites during 1978–1979. A relation was found between leaf nitrate-N concentrations and cabbage yields when the heading stage was approximately reached, or about 33 and 43 days after transplanting early and late cultivars, respectively. Soil nitrate-N concentration in samples taken at different periods during the growing season were significantly related to the rates of applied N fertilizer (r = 0.20* to 0.60**). The increase in soil nitrate-N with N fertilization seemed, however, to be confined to a depth of 25 and 50 cm. Nitrate-N accumulation seems possible with a rate of 180 kg N/ha during some growing seasons.