Mineral Nitrogen Availability Research Articles

Nitrogen balance during growth of cauliflower

The potential for loss of nitrogen to the environment during growth of cauliflower was investigated. A comparison was made between cauliflower growth and nitrogen uptake without, and with, nitrogen application of the recommended amount (=225 kg ha −1 minus mineral nitrogen in the soil layer 0–60 cm, applied at planting) on sandy clay soils under natural rainfall conditions. In two experiments, with low mineral nitrogen availability at planting, the quality and yield were reduced when no nitrogen was applied. The rate of nitrogen uptake by the crop rapidly increased from about four weeks after planting. Concurrently the amount of mineral nitrogen in the soil started to decrease. Most of the nitrogen was taken up from the 0–30 cm soil layer. The amount of nitrogen in the crop at harvest with the recommended amount of nitrogen applied ranged from 170 to 250 kg ha −1, while 7–100 kg ha −1 mineral nitrogen remained in the soil (0–60 cm layer). Crop residues contained about 95–140 kg ha −1 nitrogen. No evidence was found for leaching of fertilizer nitrogen during crop growth. With the recommended amount of nitrogen applied, during crop growth the measured amount of nitrogen in the crop and soil (0–60 cm), generally, was lower than the amount of available nitrogen (calculated as the amount of nitrogen in the crop and soil without nitrogen application plus the amount of fertilizer nitrogen applied). No period could be indicated in which there was a particularly great difference between the measured and calculated amount of nitrogen in the crop + soil system. It is concluded that the potential for loss of nitrogen to the environment is greater after crop harvest, when nitrogen may be lost from crop residues and soil, than during growth. Perspectives to reduce nitrogen fertilizer input by split application are discussed.

Soil mineral nitrogen availability was unaffected by elevated atmospheric pCO2 in a four year old field experiment (Swiss FACE).

The effect of elevated (60 Pa) atmospheric carbon dioxide partial pressure (pCO2) and N fertilisation on the availability of mineral N and on N transformation in the soil of a Lolium perenne L. monoculture was investigated in the Swiss FACE (Free Air Carbon dioxide Enrichment) experiment. The apparent availability of nitrate and ammonium for plants was estimated during a representative, vegetative re-growth period at weekly intervals from the sorption of the minerals to mixed-bed ion-exchange resin bags at a soil depth of 5 cm. N mineralisation was measured using sequential coring and in situ exposure of soil cores in the top 10 cm of the soil before and after the first cut in spring 1997. High amounts of mineral N were bound to the ion exchange resin during the first week of re-growth. This was probably the combined result of the fertiliser application, the weak demand for N by the newly cut sward and presumably high rates of root decay and exudation after cutting the sward. During the first 2 weeks after the application of fertiliser N at the first cut, there was a dramatic reduction in available N; N remained low during the subsequent weeks of re-growth in all treatments. Overall, nitrate was the predominant form of mineral N that bound to the resin for the duration of the experiment. Apparently, there was always more nitrate than ammonium available to the plants in the high N fertilisation treatment for the whole re-growth period. Apparent N availability was affected significantly by elevated pCO2 only in the first week after the cut; under high N fertilisation, elevated pCO2 increased the amount of mineral N that was apparently available to the plants. Elevated pCO2 did not affect apparent net transformation of N, loss of N or uptake of N by plants. The present data are consistent with earlier results and suggest that the amount of N available to plants from soil resources does not generally increase under elevated atmospheric pCO2. Thus, a possible limiting effect of N on primary production could become more stringent under elevated atmospheric pCO2 as the demand of the plant for N increases.

GRIZZLY BEAR DIGGING: EFFECTS ON SUBALPINE MEADOW PLANTS IN RELATION TO MINERAL NITROGEN AVAILABILITY

Grizzly bears (Ursus arctos horribilis) affect plant distributions and mineral nitrogen availability when they forage by digging for the bulbs of glacier lilies (Erythronium grandiflorum) growing in subalpine meadows of Glacier National Park, Montana, United States. Our working hypothesis is that grizzly bears structure plant communities and in- fluence nitrogen availability when they selectively dig for preferred plants. In this paper, we report on differences found in recently disturbed digs (<5 yr old) when compared to adjacent, undisturbed meadow. We used ion exchange resin bags to determine the availability of mineral nitrogen in grizzly bear digs compared to undisturbed meadow. Soil in digs contained significantly more ammonium-N and nitrate-N than adjacent, intact meadow. Glacier lily bulbs reve- getating bear digs had higher tissue nitrogen and water-soluble carbohydrate concentrations than lilies in undisturbed meadow. Mature glacier lilies in digs produced twice as many seeds as did those in adjacent meadow. Glacier lily seedlings establish best on bare mineral soil, which in these meadows is found primarily in bear digs. Therefore, grizzly bear digging may benefit old, deeply seated plants that survive digging and reproduce. Digs overlapped spatially, meaning that grizzly bears were returning to dig in patches disturbed in previous years, perhaps in response to easier digging conditions and more nutritious glacier lily bulbs. To test the idea that the observed increase in mineral nitrogen was due to the physical disturbance of grizzly bear digging and not bear choice of sites already high in nitrogen or bear excretion, we created experimental digs. Ammonium-N and nitrate-N levels in- creased significantly following our digging treatment, just as we had observed in the natural bear digs. Although we do not know how a bear chooses an initial digging site, this disturbance has the potential for influencing long- and short-term plant community structure.

Grizzly Bear Digging: Effects on Subalpine Meadow Plants in Relation to Mineral Nitrogen Availability

Grizzly Bear Digging: Effects on Subalpine Meadow Plants in Relation to Mineral Nitrogen Availability

Mineralization of nitrogen in a clayey loamy soil amended with organic wastes enriched with Zn, Cu and Cd

This paper deals with the evaluation of the availability of mineral nitrogen in soil amended with different organic wastes (sewage sludges, farm manure, and compost of municipal solid wastes) and the impact of an additional amount of Cu, Zn and Cd on N-mineralization. Net rates of mineralization fluctuated in the soil amended with organic wastes between 11·67 and 33·61 mg kg −1. The decreasing order of mineralization, expressing a decreasing order of microbiological activity, was: soil+sludges > soil+manure > soil+compost > soil. From the kinetic study, it was seen that the mineralization process could be divided into two main periods: the first was from soil moistening up to the fourth week and the second from week 8 to week 16. The first phase of incubation was a period of microbial adaptation to the new environment of soil amended with organic wastes and enriched with Cu, Zn and Cd. This phase was often marked by N consumption-immobilization. The second phase was characterized by active kinetics of mineralization and intense microbial activity. The influence of the organic amendments according to the value of N 0 (the N-mineralization potential) was: N 0 (soil) < N 0 (compost) < N 0 (manure) < N 0 (sludges). The inhibitory effect of the added metals on N-mineralization was: Cd > Cu > Zn. For many reasons, the global effect of metals on N-mineralization was very variable. A sufficiently long latent time (i weeks) was needed for tolerant microorganisms to release or to start N-mineralization.

Foliar macronutrient concentrations of forest understorey species in relation to Ellenberg's indices and potential relative growth rate

In order to investigate broad patterns of variation of the foliar mineral nutrient concentrations of herbaceous plant communities in the ground layer of W Europe forests, correlations were examined between Ellenberg's indices (N-index: mineral nitrogen availability, R-index: pH, F-index: soil moisture and L-index: light intensity) and literature values of macronutrient concentrations for 84 forbs and 39 graminoid species. Significant, positive correlations were found between the R-index and the plants' concentration of Ca and K (forbs only) and between the N-index and the plants' concentration of K, P (forbs only) and N (forbs and graminoids). Multiple regressions showed that the N-index was the best predictor of the plants' concentration of N (forbs and graminoids), P (forbs) and Ca (graminoids) and the R-index of the plants' concentration of Ca and K (forbs). The mineral nutrient concentrations of graminoids were lower and less strongly correlated with Ellenberg's indices than those of forbs. It is argued that the mineral nutrient concentrations in the plants match the availability of mineral nutrients in the soil for N, P (N-index) and Ca (R-index), but not for K and Mg. Significant, positive correlations were found between potential relative growth rate and the concentration of some elements (N, P, K and Ca in forbs, Ca and Mg in graminoids). This suggests that the increase in the concentration of these elements in plants along fertility gradients is due, at least partly, to genetically controlled alterations of leaf anatomy associated with increasing potential relative growth rate.

Elevated CO2 alters belowground exoenzyme activities in tussock tundra

A three-year exposure to a CO2 concentration of 680 μmol mol-1 altered the enzymic characteristics of root surfaces, associated ectomycorrhizae, and in soils surrounding roots in a tussock tundra ecosystem of north Alaska, USA. At elevated CO2, phosphatase activity was higher on Eriophorum vaginatum root surfaces, ectomycorrhizal rhizomorphs and mantles associated with Betula nana roots, and in Oe and Oi soil horizons associated with plant roots. Also, endocellulase and exocellulase activities at elevated CO2 were higher in ectomycorrhizal rhizomorphs and lower in Oe and Oi soil horizons associated with roots. These results suggest that arctic plants respond to raised CO2 by increasing activities associated with nutrient acquisition, e.g. higher phosphatase activities on surfaces of roots and ectomycorrhizae, and greater cellulase activity in ectomycorrhizae. Changes in enzyme activities of surrounding soils are consistent with an increase in carbon exudation from plant roots, which would be expected to inhibit cellulase activities and stimulate phosphatase activities of soil microflora. These data were used to modify existing simulation models describing tussock phosphatase activities and litter decay. Model projections suggest that observed increases in phosphatase activities at 680 μmol mol-1 CO2 could augment total annual phosphorus release within tussocks by more than 40%, at present levels of root and ectomycorrhizae biomass. This includes a nearly three-fold increase in potential phosphatase activity of E. vaginatum roots, per unit of surface area. Observed reductions in cellulase activities could diminish cellulose turnover by 45% in soils within rooting zones, which could substantially increase mineral nitrogen availability in soils due to lowered microbial immobilization.

Soil mineral nitrogen availability to young maize plants as related to root length density distribution and fertilizer application method

Minirhizotron observations from 4 experiments in 1992 and 1993 with maize on a sandy soil in the Wageningen Rhizolab, Netherlands, showed strong vertical and lateral root density gradients during the first 9 weeks after emergence. Root length density (Lrv), as determined in core samples 9 weeks after emergence, was positively related (P

Comparison of legume-based cropping systems at Warra, Queensland. 2. Mineral nitrogen accumulation and availability to the subsequent wheat crop

Mineral nitrogen release following legume-based cropping systems for restoring the fertility of a Vertisol and the yield response and N uptake of subsequent wheat crops was studied. Legume phases of pastures, including a 4 year grass+legume ley, and lucerne and medic leys (~1 year) were terminated in October 1988 or 1989 and rotated with wheat. Chickpea-wheat rotations matched those of lucerne and medic leys. Mineral N accumulations during a subsequent fallow period were determined by core sampling to 1.5 m in October, February and May. Grain yield and N uptake of wheat enabled comparisons of the fertility restorative effects of the various systems relative to continuous wheat cropping. Averaged for two fallow periods, increases in mineral N down to 1.2 m depth were 93, 91, 68, and 37 kg/ha following grass+legume, lucerne and medic leys, and chickpea, respectively, compared with the continuous wheat treatment. Wheat yields were generally lower in 1989 (1.85–2.88 t/ha) than in 1990 (2.08–3.59 t/ha) following all leys and crops due to seasonal conditions. There was a grain yield increase of 0.11 and 0.52 t/ha in 1989 and 1.23 and 1.26 t/ha in 1990 following lucerne and medic leys, respectively and 0.85 t/ha in 1990 following a 4 year grass+legume ley. Following chickpea there was a yield increase of 0.81 and 1.36 t/ha in 1989 and 1990 respectively. Nitrogen uptake by wheat was increased by 40 and 49 kg/ha in 1989 and 48 and 58 kg/ha in 1990 following lucerne and medic leys respectively and 63 kg/ha in 1990 following a 4 year grass+legume ley. Following chickpea N uptake by wheat was increased by 27 and 32 kg/ha in 1989 and 1990 respectively. Grain protein concentration of wheat was substantially higher following all pasture leys (11.7–15.8%) than following wheat (8.0–9.4%) or chickpea (9.4–10.1%). Therefore, there was substantial evidence of the effectiveness of pasture leys in soil fertility restoration, as reflected in mineral N, yield response and N uptake by subsequent wheat crops.

Vinyl-film mulch: a practice for sweet potato ( Ipomoea Batatas Lam. var. Edulis Makino) cultivation to reduce nitrate leaching

Under conventional cultivation practices in Southern Kyushu, Japan, a considerable amount of nitrate-N is leached from agricultural fields into ground water. The leaching processes are accelerated by high permeability of the volcanic ash soil, high rainfall and high summer temperatures. The present work was instigated to study the possibilities of controlling nitrate-N leaching by regulating the infiltration of rain water in the soil, the source of percolation below the root zone. Nitrate-N leaching from the root zone of sweet potatoes to deeper soil layers was compared in three treatments: maximum soil surface mulching with 0.03 mm vinyl-film with holes at ridge tops to supply plants with enough soil moisture to meet the crop water requirement (maximum vinly-film mulch, MVM); applications of fertilizer containing a nitrification inhibitor dicyaniamide (DCD); and conventional cultivation practices. NPK compound fertilizer (N 8P 5.2K 16.6) containing the ammonium form of nitrogen 900 kg·ha −1 and PK compound fertilizer P 8.7K 16.6 600 kg·ha −1 were applied in the MVM and conventional plots. DCD-fertilizer (N 15P 6.5K 12.5), maintaining the same rate of absolute N with adjustment of P and K using fused magnesium phosphate (P 8.6) and potassium chloride (K 41.5), were applied to the DCD plots. MVM increased surface run-off, resulting in least percolation among the treatments. The highest nitrate-N concentration, taken as an average for 2 years, in soil-water periodically sampled throughout the growing period at 210 cm depth below surface, was found 1.8 ppm in MVM, whereas in DCD and in conventional treatments the same was measured as 8.7 and 5.2 ppm, respectively, indicating the lowest level of nitrate leaching to be in the MVM treatment. The highest availability of mineral nitrogen in the root zone of the MVM treatment was confirmed by the highest plant-top-uptake of nitrogen, Leaf Area Index and vine growth. DCD fertilizer did not contribute to the control nitrate-N leaching. There was no significant difference in root yields among the three treatments.

Simulated effects of precipitation and nitrogen on Serengeti grassland productivity

In the Serengeti National Park, Tanzania, precipitation and soil nitrogen vary greatly between northwestern tallgrass areas and southeastern shortgrass areas, with the tallgrass having higher total precipitation and lower soil fertility. We used a model of grassland productivity, carbon/nitrogen cycling, and abiotic factors to test the hypothesis that tallgrass productivity is limited primarily by nitrogen availability while shortgrass productivity is limited by water. Under observed grazing intensities and ungrazed conditions, precipitation exerted primary control over grassland productivity for both regions, with differences in soil texture mediating soil water availability to the grasses. Mineral nitrogen availability interacted with water availability to influence productivity at precipitation levels ⩾ 130% of the mean. Nitrogen mineralization and precipitation were positively related for each grassland type, however, nitrification varied both between grassland types and between grazed and ungrazed conditions. Combined mineralization and nitrification could not maintain soil mineral nitrogen levels in the face of plant nitrogen uptake stimulated by increased precipitation, thus providing the mechanism by which nitrogen becomes a secondary limiting factor for both grasslands. Model experiments indicated that the pattern of primary limitation by precipitation and secondary limitation by nitrogen was robust to model assumptions concerning ungulate deposition of urine and dung nitrogen to the soil.

Site-factor Influence on Barley Response to Fertilizer in On-farm Trials in Northern Syria: Descriptive and Predictive Models

SummaryThe effects of site and rate of application of fertilizer on the grain and straw production of barley were investigated in 75 trials on representative farmers' fields. Grain and straw production were strongly but curvilinearly correlated with growth-period rainfall over the range 136–568 mm, almost irrespective of soil type, previous crop or fertilizer rate, and responded positively to applied nitrogen and/or phosphorus in 74 of the trials. Responses to nitrogen increased and those to phosphorus decreased with increasing rainfall. Yields tended to be lower but responses to nitrogen were higher where barley followed barley and were influenced by the availability of phosphate and mineral nitrogen in the soil at planting time.These results are summarized in regression equations, which express yield quadratically in terms of fertilizer rates, seasonal rainfall and their interactions over the full 75-trial data set and within representative sub-sets. The wide differences in crop response to fertilizer highlight the problem of recommending fertilizer rates for a low and variable rainfall environment. Simple second-order multiple regressions for different geographical areas, rainfall zones, crop rotations etc., based on mean rainfall values, account for around 40% of the variance in yield response to nitrogen and phosphorus fertilizer; only a small proportion of the remaining variance appears attributable to rainfall variability. Alternatively, yield may be expressed as a function of fertilizer rate and rainfall using rainfall probability values derived from long-term records. This can be used to estimate the probabilities of predetermined yield responses for specified sites and fertilizer rates and to produce maps of those probabilities.

Factors influencing the availability of mineral nitrogen in clay soils of the brigalow (Acacia harpophylla) region of Central Queensland

Microbiological and chemical assays were performed on clay soils from woodland (Acacia harpophylla-Casuarina cristata), grassland (Panicurn maximum var trichoglume-Chloris gayana) and cropland (Vigna mungo) in the brigalow region of Central Queensland. Over a 15 month period, the microbial biomass C in the top 3.5 cm of native brigalow woodland soil was on average 3630 8g C g-l, 50% more than an associated perennial pasture and over 400% more than an annually cropped soil. Microbial biomass N (575 8g N g-l) in woodland soil was on average 41% and 270% higher than in pasture and cropped soils respectively and highly correlated with seasonal soil moisture content. Viable counts of bacteria were consistently lower (average 69.2%) in the 0-3.5 cm and 3.5-7.5 cm strata of woodland soil compared with pasture and annual crop sites. Soil NO-3- N levels increased two fold in the upper 3.5 cm of the woodland site during low rainfall periods. This increase may be attributed to a more efficient distribution of mineral N mediated by the increased presence of a fungal population in this community. Leaching may also play a significant role in the distribution of plant available N in the brigalow region as suggested by the inverse relationship N = 54.11-0.67 R (P&lt;0.01), where N is soil NO-3-N (8g N g-l) and R is rainfall in the preceding 3 month period (mm month-1).

Nitrogen status and mineralization in natural and disturbed mediterranean forests and coppices

Past and current work on biological processes related to nitrogen fluxes and cycling in natural and disturbed Mediterranean forest sites are discussed. In natural conditions, the main point reviewed is mineral nitrogen availability in the soil, and particularly the process of mineralization (ammonification, nitrification) in the field as well as nitrogen uptake by Pinus pinea. Some aspects of nitrogen translocation within the trees are also considered. Perturbation of the nitrogen status, and especially nitrogen mineralization, as a result of manipulation of forest sites are discussed by comparing both a holm oak coppice with a clearcut and a Pinus halepensis woodland before and after prescribed fire.

Nutrient Availability Under Trickle Irrigation: II. Mineral Nitrogen

AbstractThe effects of irrigation and fertilizer application on nitrate, nitrite, and ammonium concentration in a Chromic Luvisol were studied in an orchard that had been trickle irrigated for 5 years. Immediately before the first irrigation of the season, mean plot nitrate‐N was 5 ppm; 8 h of irrigation reduced this to 0.5 ppm. Nitrite concentration fell from 0.8 to 0.4 ppm in the same period. During irrigation ammonium concentration rose from 7.1 to 13.5 ppm (the average rate of increase being 0.8 ppm/h) in the surface 6‐cm depth of soil extending up to a distance varying from 30 to 65 cm from the outlet. There was no evidence that nitrate or nitrite accumulated at the A/B horizon boundary and it is likely that the loss was due to denitrification.Ammonium concentration decreased rapidly as the soil dried out and 8 h after the end of irrigation it had fallen from 13.5 to 8.5 ppm. As there was no change in the nitrate concentration in this region during the same 8‐h period the ammonium was being immobilized rather than nitrified. The only place where nitrification took place during the first 3‐d cycle was immediately below the fertilizer band at site D where nitrate concentration rose from 0 to 15 ppm in 3 d. Mean plot nitrate‐N at the end of the first cycle was 2.6 ppm. Some 32 cycles later at the beginning of the midseason 3‐d cycle nitrate‐N had fallen to 0.6 ppm. Neither nitrate nor nitrite varied with time during the midseason 3‐d cycle. Ammonium concentration rose significantly over the region extending from at least 12 cm below the surface under the outlet to the 3‐ to 6‐cm depth 65 cm away from the outlet. Over this volume of soil ammonium‐N increased from 3.9 to 19.4 ppm during irrigation. In the 4 h after the end of irrigation the ammonium concentration decreased and there was no significant difference between the pre‐ and post‐irrigation ammonium concentrations within the volume defined above. Apparently all the ammonium released during irrigation and not taken up by plants was immobilized by the soil microbial population. The amount of ammonium released was greater in the midseason (15.5 ppm) than in the first 3‐d cycle (6.4 ppm). Ammonium release rate during the midseason irrigation was 1.3 ppm N · h−1. There were no significant changes in nitrate, nitrite, or ammonium during the midseason 1‐d cycle.The results obtained for five 3‐d irrigation cycles in early summer again demonstrated that the decrease in nitrate during the irrigation cycle was accompanied by an increase in ammonium. The phenomena was part of a continuous cycle which increased the mineral nitrogen availability during the wet portion of every 3‐d cycle.

Response of Native Grassland Legumes to Water and Nitrogen Treatments

The response of native shortgrass prairie legumes to water and nitrogen additions was evaluated utilizing a replicated factorial design of two water and two nitrogen treatments. Responses measured were densities and aboveground biomass by species. Water treatment greatly increased both density and biomass of legumes, presumably because of more favorable conditions for nitrogen fixation and increased competitive advantage under nitrogen deficient conditions. The availability of nitrogen, more than any other mineral element, is a critical determinant of both the structure and productivity of grassland plant communities (Date 1973). Additionally, mineral nitrogen supplies to the plant community largely determine the value of the biomass produced as forage for consumers. In native grasslands nitrogen-fixing plants are presumed to occupy an important position in nitrogen cycling although for most grasslands very little is known about the ecology or functional significance of native legumes (Becker and Crockett 1976). This is particularly true of the semiarid grasslands of the Great Plains of North America. The majority of the information available concerning the ecology of legumes in these grasslands is available as an incidental portion of the data collected on the dominant grassland plants (Albertson 1937; Hanson and Whitman 1938; Dyksterhuis 1946; Brown 1971; Hyder et al. 1975). As a first step in understanding the functional role of legumes in a shortgrass prairie, we provide basic phytosociological data for legumes under ambient environmental conditions and results from experimental manipulation of soil water and mineral nitrogen availability.

The availability of mineral nitrogen in a wheat soil from southern New South Wales

In a red-brown earth soil from Wagga Wagga the fluctuations in the level of mineral nitrogen (ammonia plus nitrate-nitrogen) and its availability to wheat under growing period rainfalls of 6 inches and 16 inches were studied. Ammonia-nitrogen did not exceed 8 lb nitrogen per acre 6 inches but showed statistically significant short term fluctuations. Mineral nitrogen decreased steadily from the 4-5 leaf stage of plant growth, reaching minimum values in the ear-emergence period when a temporary nitrogen deficiency occurred. Following rainfalls of about one inch or more, conditions favoured biological activity and nitrogen was mineralized, absorbed by the crop and/or leached down the profile. In one season a release of mineral nitrogen about two weeks before flowering contributed an estimated 20-30 per cent of the total nitrogen uptake of the crop. Nitrogen uptake by the wheat crop ceased after flowering and subsequent changes in mineral nitrogen level reflect the net result of mineralization and demineralization processes, and nitrogen uptake by weeds, particularly skeleton weed. Absorption of nitrogen from the profile depended upon seasonal conditions, with the surface 18 inches suppling the greater part of the nitrogen absorbed by the crop. This indicates the need to sample regularly to at least a depth of 18 inches, particularly during the period from 4-5 leaf to flowering, when studying the relation between mineral nitrogen and crop growth. The data suggest that the response of wheat, as measured by grain yield and protein content, to the higher levels of mineral nitrogen in the improved soils of southern New South Wales is determined by soil moisture levels, particularly in the post-flowering period.