N Derived From Fertilizer Research Articles

Long-term N fertilization reduces uptake of N from fertilizer and increases the uptake of N from soil

Long-term supply of synthetic nitrogen (N) has the potential to affect the soil N processes. This study aimed to (i) establish N response curves to find the best balance between inputs and outputs of N over four ratoons; (ii) use 15N-labeled fertilizer to estimate the N recovery efficiency of fertilizer applied in the current season as affected by the N management in the previous three years. Nitrogen rates (control, 60, 120, and 180 kg ha−1 N) were applied annually in the same plots after the 1st, 2nd, 3rd, and 4th sugarcane cycles. Sugarcane yield, N uptake, and N balance were evaluated. In the final season, 100 kg ha−1 of 15N was also applied in the microplots to evaluate the effect of previous N fertilization on N derived from fertilizer (NDF) and N derived from soil (NDS). Sugarcane yields increased linearly with the N rates over the four sugarcane-cycles. The best balance between the input of N through fertilizer and N removal by stalks was 90 kg ha−1 N in both the 1st and 2nd ratoons, and 71 kg ha−1 N in both the 3rd and 4th ratoons. Long-term application of N reduced NDF from 41 to 30 kg ha−1 and increased NDS from 160 to 180 kg ha−1 N. A key finding is that long-term N fertilization has the potential to affect soil N processes by increasing the contribution of soil N and reducing the contribution of N from fertilizer.

Grain yield, efficiency and the allocation of foliar N applied to soybean canopies

Soybean [Glycine max (L.) Merr.] grain yield is closely associated with the level of optimal nitrogen (N) supply, especially during the reproductive stages. Foliar fertilization with low rates of N have been considered as a strategy for furnishing additional N and enhancing grain yields. Field studies using 15N tracer were conducted over two growing seasons to investigate the impact of foliar N fertilization on grain yield, plant N content, the amount of N derived from fertilizer (NDFF) and N recovery efficiency (NRE). Four foliar N rates (0, 1300, 2600 and 3900 g ha−1) were supplied by two equal split applications at the R1 and R3 stages. Foliar N fertilization of soybean canopies did not affect grain yield, grain N content, shoot N content nor plant N content. Total NDFF was increased from 0.7 to 2.0 kg ha−1 across the N rates. Nonetheless, NRE was unaffected by foliar N fertilization, which averaged 53 %. Soybean plants allocated the same amount of N fertilizer to both grains and shoots. No significant effects of low rate foliar N fertilization were registered on soybean grain yield nor plant N content, despite considerable N fertilizer recovery by plant organs.

Competition for 15N-labeled nitrogen in a jujube tree (Zizyphus jujuba Mill.)/wheat (Triticum aestivum L.) agroforestry system in northwestern China

The degree of tree-crop competition for nitrogen (N) and its effect on fertilizer-use efficiency and N movement were examined in a jujube tree (Zizyphus jujuba Mill.)/wheat (Triticum aestivum Linn.) agroforestry system during 2011–2012. Assessment of competition was accomplished via the installation of an experiment with five imbedding depths (20, 40, 80, 120 and 200 cm) of 15N-enriched CO(NH2)2 and two configuration patterns (sole and intercropped treatment). The percentage of N derived from fertilizer (NDFF) and fertilizer-use efficiency (UFN) were determined using 15N-enriched CO(NH2)2 (5.22% atom enrichment) applied at 8 g N per plant. Land equivalent ratios of the jujube/wheat intercropping system reached maximum ratios of 1.45 for grain (fruit) yield and 1.67 for biomass in 2011 and 1.38 for grain (fruit) yield and 1.59 for biomass in 2012. The alley cropping yield decreased significantly compared to sole-cropped plants in both years, as did the biomass of intercropped wheat in 2012. This study showed a significant difference in nitrogen acquisition between intercropping and the expected value for the various depths in both years. The %NDFF of the two plants showed significant differences between intercropping and the expected value at various depths in both years, and the intercropped %NDFF was higher than the expected value. The total UFN data, which represented an increase in response to intercropping, indicate that plants in the intercropping treatment had a higher UFN than the expected value. The UFN for jujube trees in all treatments was lower than that for wheat, indicating less uptake and utilization of N fertilizer. Management interventions, particularly those that increase fertilizer in the shallow layer may be critical for the success of this system.

Understanding N timing in corn yield and fertilizer N recovery: An insight from an isotopic labeled-N determination.

Early fertilizer nitrogen (N) application on cover crops or their residues during the off-season is a practice adopted in Brazil subtropical conditions under no-tillage corn (Zea mays L.) systems. However, the effect of early N application on yield, plant N content, and N recovery efficiency (NRE) for corn is not yet well documented. Five fertilizer N timings in an oat-corn system were evaluated in two studies utilizing an isotopic-labeled N determination, 15N isotope. The N fertilization timings were: (i) oat tillering, (ii) 15 days before corn planting time, over the oat residues, (iii) at corn planting time, (iv) in-season at the three-leaf growth stage (V3), and (v) in-season split application at V3 and six-leaf (V6) growth stages. Based on the statistical analysis, the N fertilization timings were separated into three groups: 1) N-OATS, designated to N applied at oat; 2) N-PLANT, referred to pre-plant and planting N applications; and 3) N-CORN, designated to in-season corn N applications. Corn yield was not affected by the N fertilization timing. However, the N-CORN N fertilization timings enhanced NRE by 17% and 35% and final N recovery system (plant plus soil) by 16% and 24% all relative to N-OATS and N-PLANT groups, respectively. Overall, N-OATS resulted in the largest N derived from fertilizer (NDFF) amount in the deeper soil layer, in overall a delta of 10 kg N ha-1 relative to the rest of the groups. Notwithstanding corn yield was not affected, early N fertilization under subtropical conditions is not a viable option since NRE was diminished and the non-recovery N increased relative to the in-season N applications.

Spring Nitrogen Uptake, Use Efficiency, and Partitioning for Growth in Iris germanica ‘Immortality’

This study investigated how spring nitrogen (N) application affects N uptake and growth performance in tall bearded (TB) iris ‘Immortality’ (Iris germanica L.). Container-grown iris plants were treated with 0, 5, 10, 15, or 20 mm N from 15NH415NO3 through fertigation using a modified Hoagland’s solution twice a week for 6 weeks in Spring 2013. Increasing N rate increased plant height, total plant dry weight (DW), and N content. Total N content was closely related to total plant DW. The allocation of N to different tissues followed a similar trend as the allocation of DW. In leaves, roots, and rhizomes, increasing N rate increased N uptake and decreased carbon (C) to N ratio (C/N ratio). Leaves were the major sink for N derived from fertilizer (NDFF). As N supply increased, DW accumulation in leaves increased, whereas DW accumulation in roots and rhizomes was unchanged. This indicates increasing N rate contributed more to leaf growth in spring. Nitrogen uptake efficiency (NupE) had a quadratic relationship with increasing N rate and was highest in the 10 mm N treatment, which indicates 10 mm was the optimal N rate for improving NupE in this study.

Uptake and allocation of nitrogen applied at low rates to soybean leaves

Foliar nitrogen (N) fertilization of soybean crops is a practice that is being adopted in Brazil because soybean crops require N during the reproductive stages and certain soils have low N availability and reduced biological N fixation (BNF). Thus, low rates of leaf N are being used without scientific evidence for supporting the practice. The aim of this study was to analyze the uptake efficiency and allocation of N provided by foliar applications of low rates of urea-N during the soybean reproductive stage. The study was conducted in Taquarituba, Sao Paulo State (SP), Brazil during the 2012/13 and 2013/14 crop seasons. Rates of 0, 650, 1300 and 1950 g N ha−1 applied at the R1 or R3 growth stage were analyzed. Grain yield, N extraction by the grains, shoots (including leaves + stems + pod husks), total plants (grains + shoots), N derived from fertilizer (NDFF), 15N accumulation in grains or shoots, and fertilizer N-use efficiency by plant (NUE) were measured using 15N. Foliar application of 1950 g ha−1 of N increased the N content in the shoots by up to 22 kg ha−1. Regardless of the year, the application during R3 yielded the highest NDFF values in the grains that were, on average, 20 % higher than in R1. However, the highest mean values of NDFF and NUE were obtained from the R3 or R1 applications when there was less rainfall. Despite the high NUE (64 %), foliar applications of low rates of N on soybean crops did not increase the seed yield. Most of the fertilizer N was allocated to the grains, especially when applied at the R3 growth stage. The NUE of the soybean crop ranged from 51 to 72 %, and it was dependent on the phenological stage of the crop and climate conditions during crop growth in addition to the timing of fertilizer application. Foliar application of low rates of N on soybean crops did not increase seed yield.

Fertilizer N uptake of paddy rice in two soils with different fertility under experimental warming with elevated CO2

Only limited information is available in the research area on the effect of elevated CO2 concentration ([CO2]) and air temperature (Tair) on the fertilizer N uptake by rice. This study was conducted to investigate changes in rice uptake of N derived from fertilizer (NDFF) and soil (NDFS) as well as fertilizer N uptake efficiency (FUE) with elevated [CO2] and Tair in two soils with different fertility. Rice (Oryza sativa L.) plants were grown with 15N-urea for two growing seasons (2007 in the less fertile and 2008 in the more fertile soil) in temperature gradient chambers under two (ambient and elevated) levels of [CO2] and Tair regimes. At harvest, dry matter (DM) and N uptake amount of rice compartments (root, shoot, and grain) were determined. The DM of whole rice increased (P < 0.01) with co-elevation of [CO2] and Tair in both years (by 28.0 % in 2007 and by 27.4 % in 2008). The DM in 2008 was greater than that in 2007 by 48.1 to 63.1 % probably due to better soil fertility as well as longer sunshine hours (456 h vs. 568 h). Co-elevation of [CO2] and Tair increased total N uptake, NDFF, and NDFS by 19.4 to 29.1 % in general compared to the ambient conditions. The FUE increased with co-elevation of [CO2] and Tair from 46.5 to 59.5 % in 2007 and from 36.7 to 43.8 % in 2008. The projected global warming with elevated [CO2] is expected to increase FUE via enhanced DM accumulation with less increments in the soils that have higher indigenous soil N availabilities.

Nitrogen in sugarcane derived from fertilizer under Brazilian field conditions

Nitrogen (N) fertilization of sugarcane crops is a common practice used to reach sustainable levels of productivity, both for plant cane and especially for the ratoon. However, when evaluating the amount of N in the plant derived from fertilizer (NDDF) at harvest, this contribution is approximately 20% of total plant biomass N, which raises questions regarding the efficiency of N fertilization. The goal of this study was to evaluate the N derived from fertilizer (NDFF) during the sugarcane crop development, for both plant cane and first ratoon crop cycles. Two field experiments were performed in São Paulo State, Brazil, in Arenic Kandiustults and in Typic Eutrustox. The sugarcane was mechanically harvested without burning. N fertilizer for both the plant cane (doses of 40, 80 and 120 kg ha −1 of N as urea) and the first ratoon (doses of 50 and 100 kg ha −1 of N as ammonium sulfate) was labeled 15N. The results showed that NDFF contributed up to 40% of the total N in the plant cane at initial stages of development. The magnitude of this contribution decreased during stages of maturity to approximately 10% of total N at harvest. In the first ratoon, application of N fertilizer was more effective for crop nutrition, constituting up to 70% of total N in initial stages of development and decreasing through the cycle, reaching approximately 30% at harvest. Therefore, studies that evaluate NDDF only at harvest can lead to underestimating the role of N fertilizer for sugarcane nutrition. The higher NDFF in ratoon explains why this crop cycle presents a more consistent response to N fertilization than plant cane, as observed in several studies developed under Brazilian conditions in the last decades.

Retranslocation, Plant, and Soil Recovery of Nitrogen‐15 Applied to Bareroot Black Walnut Seedlings

Although retranslocation or nitrogen (N) derived from plants (NDFP) may account for more than 50% of the annual N demand in new growth of conifer seedlings, the proportional contribution of NDFP vs. current uptake or N derived from fertilizer (NDFF) in new growth of hardwood seedlings is relatively unknown. The current uptake was labeled with ammonium sulfate [(15NH4)2SO4] at the rate of 1.56 g N plant−1 and reared for 90 days in sand culture under greenhouse conditions, and NDFP vs. NDFF was quantified in new growth of half‐sib bareroot black walnut (Juglans nigra L.) seedlings. Nitrogen derived from plants accounted for 68 to 83% of the total N demand in new shoot growth of black walnut seedlings vs. NDFF (17 to 32%). Recovered applied fertilizer was 43% in soil and 9% in plants. The greater proportion of NDFP in new growth demonstrates the importance of retranslocation in meeting early N demand of transplanted black walnut seedlings.

Influence of Unflooded Mulching Cultivation on Nitrogen Uptake and Utilization of Fertilizer Nitrogen by Rice

Through unflooded mulching in field plots and 15nitrogen microplot tracer experiments, nitrogen (N) uptake of rice and N utilization have been studied compared with normal irrigation cultivation. The results showed that N uptake of unflooded rice and N derived from fertilizer (NDFF) of root, stem, and grain under mulching cultivation were lower than that under cultivation without mulching. However, the NDFF of rice under unflooded cultivation was higher than that under normal irrigation cultivation. The N utilization has been greatly enhanced under unflooded cultivation without mulching and unflooded plastic film cultivation with mulching as compared with normal irrigation. At the same time, there was no significant difference on the N uptake of unflooded rice among different ways of mulching cultivations. During the growth period of rice, no prominent differences were found in the soil residue, recovery, and N losses of fertilizer except the N uptake of rice between unflooded mulching and normal irrigation. The yield of rice under film mulching and straw mulching cultivation was higher than that of cultivation without mulching in the condition of unflooded cultivation, whereas the yield of rice under irrigation cultivation was higher than that under unflooded cultivation.

Nitrogen Uptake in a Range of Alternative Orchard Floor Management Systems

The percentage of N from fertilizer removed from the field by fruit trees is low. Overapplication of N in orchards has been a common practice and is a concern due to environmental and tree growth problems caused by excess N. Orchard floor management practices (OFMP) can improve the physical and chemical properties of the soil and may alter the soil biological community. Biological activity can affect mineralization rate and thus nutrient availability. The purpose of this study was to determine the effect of alternative OFMP on fertilizer N uptake. Research plots were located in Corvallis, Ore. (COR) (7-year-old `Fuji'), and Hood River, Ore. (HR) (3-year-old `Red Delicious'). Treatments were begun in 2001 in a split-plot completely randomized design with three replications. Main plot treatments were herbicide or cultivation. Subplot treatments were no amendment, bark mulch, compost, and barley/vetch mown and blown into the tree row. Depleted NH3SO4 was applied to single-tree replicates at budbreak. Trees were destructively harvested at harvest of 2003. At HR, the percentage of N derived from fertilizer (NDFF) was significantly lower in the whole tree, leaves, new wood, old wood, spurs, and roots of trees from compost than from unamended plots (P &lt; 0.05). At COR, the NDFF in the leaves, fruit, new wood, spurs and roots was significantly lower in trees from compost plots than unamended plots (P &lt; 0.05). The NDFF also tended to be lower in trees from bark mulch-treated plots than control plots, although differences were not always significant. Vetch/barley amendment resulted in NDFF similar to no amendment. There were no significant differences between the total N of trees from unamended and compost plots. Trees from compost-treated plots appear to be acquiring N from sources other than fertilizer.

Competition for15N-labeled fertilizer in a pecan (Carya illinoensis K. Koch)-cotton (Gossypium hirsutum L.) alley cropping system in the southern United States

The degree of tree-crop competition for nitrogen (N) and its effect on fertilizer-use efficiency and N movement were examined in a pecan (Carya illinoensis K. Koch)-cotton (Gossypium hirsutum L.) alley cropping system. Assessment of competition was accomplished via the installation of a belowground polyethylene root barrier in half the number of plots in order to provide two treatments–barrier and non-barrier. The percentage of N derived from fertilizer (NDF) and fertilizer-use efficiency (UFN) were determined using 15N-enriched ammonium sulfate (5% atom enrichment) applied at 89.6 kg N ha−1. In cotton, the barrier treatment resulted in higher leaf (38%), stem (66%), seed cotton (55%) and total (58%) biomass compared to the non-barrier treatment. Total N content in leaf, stem and seed cotton was 67% higher in barrier compared to non-barrier treatment. Percentage of NDF in cotton leaf and stem was significantly lower in barrier (15.8% and 17.3%, respectively) compared to non-barrier treatment (20.4% and 21.2%, respectively). For UFN, this trend was reversed, with plants in barrier treatment having a higher percentage of UFN. Root trenching did not affect pecan foliar N concentration, canopy N content, NDF or UFN. In soil, N recovery at 90–120 cm depth was lower in non-barrier treatment, indicating tree root uptake of fertilizer N. Although tree roots in non-barrier treatment had access to fertilizer N, competition was mainly for N already in the soil, since fertilizer was applied after major seasonal nutrient demands of the trees had been met. Overall, the alley cropping system in this study exhibits potential for efficient N cycling, given the apparent ability of pecan trees to intercept and uptake N fertilizer from deeper soil layers and return to surface soil via litterfall.

15N-labelled urea fertilization of a tamarack/black spruce mixed stand on a drained minerotrophic peatland: 15N in soil and tree uptake

15N-Labelled urea fertilizer was used to examine initial uptake patterns of nitrogen (N) into foliage of tamarack ( Larix laricina (Du Roi) K. Koch.) and black spruce ( Picea mariana ) Mill.) BSP.), and movement of N from point of placement through live moss and organic soil on a drained minerotrophic peatland in central Alberta, Canada. The site was ditched in Fall 1987 and 15N-labelled urea fertilizer was applied on 1 June 1989. Tree foliage and soil samples were taken periodically during the 1989 growing season. A greater proportion of fertilizer N was retained (immobilized) in peat residue of surface soil layers (0–20 cm depth) and this did not change during the study period. However, mineral- 15N concentration decreased from 76 to 19 mg 15N kg −1 between Week 2 and Week 13 following fertilizer application. Foliar % NDFF (the percentage of total N derived from fertilizer) and 15N content (amount of 15N per needle) increased rapidly for both species during the growing season. A higher proportion of fertilizer N taken up by trees was allocated to tissues of high metabolic activity, i.e. current needles. The foliar %NDFF was higher for black spruce compared with that of tamarack. This may be related to a greater size (amount of foliage and associated photosynthetic organelle) and strength (rate of biological activity) of the sink for N associated with black spruce relative to that of tamarack.