Timing Of Nitrogen Fertilizer Application Research Articles

Nitrogen fertilizer source, rate, placement, and application timing effect on sorghum (grain and forage) and corn grain yields

AbstractIdentifying the limiting nutrient, fertilizer source, rate, placement, additives, and timing of application are critical components of fertilizer management. The objective of this study was to quantify the impact of nitrogen (N) fertilizer source, rate, placement method, additives, application timing, and environment on yields of grain sorghum, forage sorghum [Sorghum bicolor (L.) Moench], and corn (for grain, Zea mays L.). Independent field experiments were conducted at 13 different environments in Kansas from 2008 through 2013 on grain sorghum, forage sorghum, and corn. Treatments were an incomplete factorial combination of four fertilizer placement methods, three fertilizer types, five fertilizer additives, three fertilizer application times, and six fertilizer rates that varied by location and across years. Results showed grain and forage sorghum yields responded to N fertilizer in environments that were not extremely dry (<136 mm) or wet (>651 mm). Corn responded to N fertilizer application only in high‐precipitation environments. For grain sorghum, where rate × placement × source × additive interaction was significant, broadcast application of urea (source) at high rates (67–134 kg N ha−1), with summer application timing, or with additive in winter (with environmentally smart nitrogen [ESN]) resulted in up to 43% greater yield compared with application of urea‐ammonium nitrate (UAN; source) and surface band (placement) at 67 kg ha−1 without additives. In the one site‐year where forage sorghum responded to fertilizer application, forage yields with preplant application of UAN at 56–140 kg ha−1 were 164% greater than the control. For corn, application of either urea or UAN fertilizer, UAN in coulter or surface band, with ESN blend, applied at planting, and at highest rates (160 kg ha−1) resulted in best yields compared with the alternatives and 110% greater yield compared with the unfertilized control. We concluded that fertilizer rate is an important management component as it consistently affected yield regardless of crop considered. Fertilizer placement and timing have crop‐specific importance as they were significant for only corn, but the main effect of additives (N stabilizers) was not significant for any of the crops. Environment and crop type influenced crop response to N fertilizer rate, timing, placement, and additives.

Annual Urea Nitrogen Contribution to the Nutrition of Cabernet Sauvignon Grapevine Grown in Sandy and Clayey Soil

The timing of nitrogen fertilizer application in vineyards can determine the amount of nitrogen (N) absorbed, distributed, and accumulated in grapevine organs. The study aimed to evaluate the annual contribution of N from urea, applied at different times in Cabernet Sauvignon, grown in sandy and clayey soil in a subtropical climate. The sandy soil received 21.42 kg N ha−1 and the clayey soil 30 kg N ha−1, both enriched with 3% excess 15N atoms, applied at different times. The N derived from the fertilizer in grapevines, at all times of N application, and in sandy and clayey soil did not exceed 8%, with the highest values being observed in annual organs, especially in the leaves. The application of N marked at the phenological stages of IBB (50% at beginning of budbreak + 50% at full budbreak) enabled greater absorption of N derived from the fertilizer by the vines grown in both sandy and loamy soil. The N present in the annual organs (leaves, berries, stalks, and shoots) and in the perennial organs (stems and canes) of Cabernet Sauvignon grown in sandy and clayey soil was derived in greater percentages from the soil.

NITROGEN FERTILIZER APPLICATION TIME EFFECT ON THE SENESCENCE AND GRAIN YIELD OF DURUM WHEAT (TRITICUM DURUM DESF.)

The experiment progressed to evaluate the effects of time nitrogen fertilizer application on the senescence of durum wheat and its association with grain yield and its components. The experimental treatments, set up in a split-plot design, used five durum wheat cultivars (Adnham, Grecale, Duma, Sardar, Svevo) as the main plots, and the time nitrogen fertilizer application (100% tillering, 100% stem elongation, and 50% tillering + 50% stem elongation stages) under two locations in Northern Iraqi conditions. The results of this study indicated that late senescence cultivars (Grecale and Svevo) produced the highest flowering date (123.89 and 123.61 days), number of spikes/m2 (267.2 and 265.6 spikes), number of grains/10 spikes (330.5 and 323.6 grains), grain yield g/m2 (532.2 and 511.6 g), and harvest index% (38.72% and 39.86%). Moreover, the time of nitrogen fertilizer application at the tillering stage (early application) influenced most of the studied traits. Finally, extending photosynthesis capacity during the grain-filling phases by delaying the rate of senescence could be a better approach to improving the grain yield of wheat cultivars.

Interaction of the coupled effects of irrigation mode and nitrogen fertilizer timing on rice yield in different regions

AbstractThe production efficiency of water and nitrogen is affected by irrigation and the nitrogen rate. However, it is unclear whether there is a coupling effect of irrigation mode and the timing of nitrogen fertilizer application on rice. Therefore, a two‐year field experiment was conducted at two sites with varying cumulative temperatures from 2018 to 2019. The effects of irrigation mode and nitrogen fertilization timing on rice yield and related physiological parameters were examined in different regions. The results showed that sites with different average temperatures had different coupling effects of water and nitrogen on crop growth. The impact of irrigation mode on yield was greater than that of nitrogen fertilizer timing at the site with a 2800 °C annual cumulative temperature (Wanchang). Alternate wetting and drying irrigation increased yield, water production efficiency and nitrogen production efficiency by 8%–10%, 31%–37% and 8%–10%, respectively. In the site with a 2500 °C annual cumulative temperature (Longjing), the coupling effect of irrigation method and nitrogen fertilization timing was significant, and continuously flooded irrigation combined with nitrogen fertilizer (40%:30%:20%:10%) improved rice yield and production efficiency by delaying senescence of leaves and increasing dry matter translocation. The results indicate that combining temperature to explore the optimal coupling mode of irrigation and nitrogen is a promising cropping technique to improve crop productivity and production efficiency in northeastern China.

Corn optimum nitrogen fertilizer rate and application timing when following a rye cover crop

Corn optimum nitrogen fertilizer rate and application timing when following a rye cover crop

Determination of Appropriate Time of Nitrogen Fertilizer Application for Maize in the Central Highlands of Ethiopia

Excessive nitrogen fertilization and improper management can cause a decrease in NUE in the maize cropping system. Most nitrogen fertilizers are applied when the corn is 4-5 weeks after planting. However, recent studies have shown that modern hybrids take up high amounts of nitrogen at the flowering stage. This suggests that a nitrogen fertilization strategy that starts at the beginning of vegetative growth and later in the flowering phase is needed to maximize the yield of hybrid maize in upland. The study was conducted in 2018-2019 in Liban, Jawi, and Toke Kutaye Districts in the West Showa Zone of the Central Highlands of Ethiopia. The research design used a randomized block design with the one-time treatment of fertilizer application consisting of six levels, namely 1/3 at planting + 1/3 at 4-5 weeks after an emergency (WAE) + 1/3 at 70-80 days after planting (DAP ); 1/3 part at planting + 2/3 part at 4-5 WAE; 2/3 share at 4-5 WAE + 1/3 at 70-80 DAP; 1/4 at planting + 1/2 at 4-5 WAE + 1/4 at 70-80 DAP; 1/2 at 4-5 WAE + 1/2 at 70-80 DAP; and full at 4-5 WAE). Nitrogen fertilization on2/3part at 4-5 WAE + 1/3 part at 70-80 DAP significantly affected plant height, cob length, grain yield, and biomass yield, but it did not influence root and stem lodging. When the data were combined over the two years, the treatment of 2/3part N application at 4-5 WAE (knee height) + 1/3 part at 70-80 DAP (before tasseling) resulted in the highest grain yield with a yield advantage of 1,598 kg/ha and gave maximum net benefit over the typically used full application at 4-5 WAE (knee height). This fertilizer management strategy could be advised for the Liban Jawi, Toke Kutaye areas, and other similar agro-ecosystem environments.

Determination of Appropriate Rate and Time of Nitrogen Application to Improve Productivity of Malt Barley (Hordium disticum L.) in Arsi Highland of Ethiopia

Barley is produced in Ethiopia in a wide range of environments and it is produced on 0.95 million hectares. But production of malt barley is quite low in Ethiopia which is 2378010.3 tones per year. There are many reasons for low yield of barley in Ethiopia, among which low soil fertility is a major reason for low productivity of this crop. This experiment was conducted to determine the appropriate rate and time of nitrogen fertilizer application for malt barley at Kofele district of Arsi zone under rain fed condition for three years. The treatments consisted of four nitrogen fertilizer rates (23kg/ha, 46kg/ha, 69kg/ha and 92kg/ha) and three different times of nitrogen application (½ at planting and ½ at tillering, 1/3 at planting and 2/3 at tillering and all at planting). Malt barley variety Ebon was used for this experiment. Randomized complete block design with split plot arrangement of treatments with three replications was used. The three years combined data indicated that biological yield and grain yield was not significantly affected by both nitrogen fertilizer rate and time of nitrogen application. But the highest biological yield (25624 kg/ha) and grain yield (7316.0kg/ha) of malt barley were recorded at the (92 kg/ha) and 46kg/ha of nitrogen fertilizer application, respectively. The combined data analysis indicated that nitrogen application rate significantly affected harvest index. The highest harvest index of malt barley 36.7 was obtained at 23 kg/ha of nitrogen application. Plant height showed highly significant difference and significance difference to nitrogen rate and timing of nitrogen application, respectively. The highest plant height (97.2cm) was recorded at 69 kg/ha of nitrogen. From timing of nitrogen application treatments, all at planting gave the highest plant height of malt barley which is 96.7cm. Spike per 50cm showed significant difference to nitrogen fertilizer rate and highest spike per 50cm of malt barley was recorded at 69 kg/ha. Even though, economic analysis was not done, 46kg/ha of nitrogen fertilizer and ½ at planting and ½ at tillering application time of nitrogen can be recommended for improving yield of malt barley at Kofele district. Keywords: Experiment, Nitrogen fertilizer, Malt barley, Yield DOI: 10.7176/JBAH/12-12-02 Publication date: June 30 th 2022

Productivity, Nitrogen Use Efficiency and Economic Benefits of Food Barley (Hordium vulgare L.) as Influenced by Stages of Nitrogen Split-Application in Central Highlands of Ethiopia

This experiment was initiated to evaluate the appropriate nitrogen fertilizer split application timing for food barley using for HB-1307 food barley variety. This experiment was done at Holeta Agricultural Research center, West Shoa, Ethiopia. The split nitrogen application times were ½ at planting + ½ at mid tillering, ½ at planting + ½ at anthesis, nil at planting + ½ mid tillering + ½ at anthesis, nil at planting + full at mid tillering, nil at planting + full at anthesis, ½ at planting + 2/3 at mid tillering, 1/3 at planting + 1/3 mid tillering + 1/3 at anthesis, nil at planting + 1/3 mid tillering + 2/3 at anthesis, 2/3 at planting + 1/3 mid tillering, 2/3 at planting + 1/3 at anthesis, full at planting and negative control. The experiment was laid out randomized complete block design with three replications. Timing of split nitrogen fertilizer applications has significant effect on the yield and yield component barley. Application of nitrogen fertilizer one third at sowing plus two third at mid tillering gave the highest grain yield. This application method gave a yield advantage of 10.7 % over the commonly practiced 1/2 at sowing and 1/2 at mid tillering. It also gave the highest economic return and agronomic Nitrogen Use Efficiency. Keywords: nitrogen fertilizer, split application timing, Nitisols, food barley DOI: 10.7176/JNSR/13-11-04 Publication date: June 30 th 2022

Nitrogen Fertilizer Application Timing Effects on Nitrous Oxide Emissions from Simulated Furrow-Irrigated Rice on a Silt-Loam Soil in the Greenhouse

Furrow-irrigation represents a growing alternative water management strategy for rice (<em>Oryza sativa</em>) production. However, optimal nitrogen (N) fertilization rates and timing for furrow-irrigated rice are still in question. Though methane emissions may be minimized without a prolonged flood, concern exists that furrow-irrigated rice may increase nitrous oxide (N₂O) production and release from frequent alternating wet and dry soil conditions.

Nitrous Oxide Consumption Potential in a Semi-Arid Agricultural System: Effects of Conservation Soil Management and Nitrogen Timing on nosZ Mediated N2O Consumption

Agricultural soils account for less than 10% of the total greenhouse gas (GHG) emissions in the United States but about 75% of nitrous oxide (N2O) emissions. Soil conservation practices, such as no-tillage, have the potential to mitigate GHG emissions. We examined the short-term consequences of no-tillage with a winter wheat cover crop (NTW) and no-tillage winter fallow (NT) on N2O emissions, N2O reducing bacterial populations, and overall soil bacterial abundance during the summer growing season in the southern Great Plains, United States. Conservation practices were coupled with nitrogen (N) fertilizer application timing (100% pre-plant, 100% mid-season, 40% pre-plant 60% mid-season, 100% pre-plant with N stabilizer). In addition, N2O emissions were measured to determine any functional effects of altering N fertilizer timing and changing bacterial populations. The combination of N treatment and conservation practice affected nosZ clade II abundance in the second year of the study. Diversity of nosZ clade II was evaluated to determine effects on non-typical N2O reducers which were highly abundant in this study. No nosZ clade II diversity effects were determined, although some clustering of conservation system and N treatments was observed in the second year. Nitrogen treatment affected N2O-N emissions during the summer of both years, likely related to overall increased microbial activity and N fertilizer application. Negative fluxes (consumption) of N2O-N were observed in every treatment and tillage combination and were most pronounced in the control (0 kg N ha−1). Negative fluxes are likely due to a combination of low inorganic-N concentrations at various points during the year and a robust clade II population driving N2O consumption. Altering conservation system and the timing of N fertilizer application affects the microbial community and will likely continue to select for unique communities as the system matures. This will also likely further impact N2O emissions from the system and may increase the rate and frequency of N2O consumption.

Effects of Nitrogen Fertilizer Quantity and Time of Application on Sorghum (Sorghum bicolor (L.) Moench) Production in Lowland Areas of North Shewa, Ethiopia

This research was conducted to assess the effect of rates and time of nitrogen fertilizer application on yield and yield components of sorghum in lowland areas of North Shewa. The treatments contained three rates of nitrogen (N) (46, 92, and 138 kg·ha−1) and three times of N application (1/2 dose at sowing and 1/2 dose at tillering (timing one); 1/3 dose at sowing and 2/3 dose at tillering (timing two); and 1/3 dose at sowing, 1/3 dose at early tillering, and 1/3 dose at tillering (timing three) including one control. Days to 50% maturity, plant height, head length, head weight, and grain yield were significantly affected by treatment effect, while days to emergency, days to heading, and thousand kernel weight showed nonsignificant effect. The maximum grain yield was 5.060, 5.169, 5.836, and 5.555 t·ha−1 from T2, T5, T8, and T10, respectively, and statistically similar yield was recorded at combination of different rates in two split applications (1/2 dose at sowing and 1/2 dose at tillering). By considering the economic status of the farmers, the applications of 46 kg·N·ha−1 in two split doses (1/2 dose at sowing and 1/2 dose at tillering stage) gave 87,122 Birr·ha−1 with a MRR of 475.61%, which gave best economic benefit. Therefore, it can be concluded that use of 46 kg·N·ha−1 in two split applications (1/2 dose at sowing and 1/2 dose at tillering stage) can be recommended for farmers for production of sorghum in the study area and other areas with similar agroecological conditions.

Optimizing Top Dressing Nitrogen Fertilization Using VENμS and Sentinel-2 L1 Data

Environmental and economic constraints are forcing farmers to be more precise in the rates and timing of nitrogen (N) fertilizer application to wheat. In practice, N is frequently applied without knowledge of the precise amount needed or the likelihood of significant protein enhancement. The objective of this study was to help farmers optimize top dress N application by adopting the use of within-field reference N strips. We developed an assisting app on the Google Earth Engine (GEE) platform to map the spatial variability of four different vegetation indices (VIs) in each field by calculating the mean VI, masking extreme values (three standard deviations, 3σ) of each field, and presenting the anomaly as a deviation of ±σ and ±2σ or deviation of percentage. VIs based on red-edge bands (REIP, NDRE, ICCI) were very useful for the detection of wheat above ground N uptake and in-field anomalies. VENµS high temporal and spatial resolutions provide advantages over Sentinel-2 in monitoring agricultural fields during the growing season, representing the within-field variations and for decision making, but the spatial coverage and accessibility of Sentinel-2 data are much better. Sentinel-2 data is already available on the GEE platform and was found to be of much help for the farmers in optimizing topdressing N application to wheat, applying it only where it will increase grain yield and/or grain quality. Therefore, the GEE anomaly app can be used for top-N dressing application decisions. Nevertheless, there are some issues that must be tested, and more research is required. To conclude, satellite images can be used in the GEE platform for anomaly detection, rendering results within a few seconds. The ability to use L1 VENµS or Sentinel-2 data without atmospheric correction through GEE opens the opportunity to use these data for several applications by farmers and others.

Timing matters: Distinct effects of nitrogen and phosphorus fertilizer application timing on root system architecture responses.

Although different plant foraging responses to the two macronutrients nitrogen (N) and phosphorus (P) are well researched, the effect of timing of fertilizer application on root system architecture (RSA) remains largely unknown. We, therefore, aimed to understand how RSA of Hordeum vulgare L. responds to timing of N and P application. Plants were grown in rhizoboxes for 38days in nutrient-poor soil and watered with nutrient solution, lacking either N or P, with the absent nutrient applied once either 2/3/4weeks after sowing. Positive controls were continuously receiving N and P and a negative control receiving both N and P only after 3weeks. We tracked root growth over time, measured plant biomass and nutrient uptake. Late N application strongly reduced total root biomass and visible root length compared with continuous NP and late P application. Root mass fractions (total root biomass/total plant biomass) remained similar over all treatments, but relative allocation (% of total root biomass) was higher in lower depth with late N application. Shoot P concentrations remained relatively stable, but the plants receiving P later had higher N concentrations. Late N application had overall more negative effects on early plant growth compared with late P. We propose that future studies under field conditions should try to disentangle the effect of timing from the nutrient availability on RSA responses and hence ultimately plant performance.

Effects of timing of nitrogen fertilizer application on responses by tropical grasses

Timing of nitrogen (N) fertilizer application can influence grass regrowth, so it is important to identify how tropical grasses respond to delays in applying fertilizer after defoliation. Our objective was to identify the effects of timing of N fertilizer application after harvest on the productive, morphogenic and structural characteristics of 3 tropical grasses: ‘Xaraés’ (Urochloa brizantha [Hochst. ex A. Rich.] Stapf cv. Xaraés), ‘Marandu’ (Urochloa brizantha [Hochst. ex A. Rich.] Stapf cv. Marandu) and ‘Tanzânia’ (Megathyrsus maximus [Jacq.] cv. Tanzânia). The experiments were performed in a greenhouse, in a completely randomized design, with 5 delays in applying N after harvesting (0, 3, 6, 9 and 12 days). Delaying fertilizer application did not affect the forage mass of Xaraés and Marandu palisade grass (7.4 and 7.8 g/pot, respectively). There was a linear decrease in number of leaves per tiller and leaf appearance rate, but tiller population density and phyllochron increased linearly as fertilizer application was delayed. Grass forage mass (12.2‒10.6 g/pot), number of leaves per tiller (3.1‒2.6 leaves/tiller) and forage accumulation rate (0.47 to 0.41 g DM/d) of Tanzânia guinea decreased linearly as N application was delayed, but tiller population density was unaffected (25 tillers/pot). Based on our results, N fertilizer should be applied to Tanzânia guinea grass pastures as soon as possible after harvest and certainly before 3 days, while there is not the same urgency with Xaraés and Marandu where fertilization could be delayed up to 12 days without significant detriment. These suggestions need to be tested in a field study before being recommended widely.

Effect of Timing of Nitrogen Split Application on Productivity, Nitrogen Use Efficiency and Economic Benefits of Food Barley (Hordium vulgare L.) in Central Highlands of Ethiopia

This study was planned to identify the appropriate nitrogen fertilizer split application timing for food barley using 'HB-1307' food barley variety. This experiment was done at Holeta Agricultural Research center, West Shoa, Ethiopia. The split nitrogen application times were ½ at planting + ½ at mid tillering, ½ at planting + ½ at anthesis, nil at planting + ½ at mid tillering + ½ at anthesis, nil at planting + full at mid tillering, nil at planting + full at anthesis, ½ at planting + 2/3 at mid tillering, 1/3 at planting + 1/3 mid tillering + 1/3 at anthesis, nil at planting + 1/3 mid tillering + 2/3 at anthesis, 2/3 at planting + 1/3 mid tillering, 2/3 at planting + 1/3 at anthesis, full at planting and negative control. The experiment was laid out randomized complete block design with three replications. Timing of split nitrogen fertilizer applications has significant effect on the yield and yield component of food barley. Application of nitrogen fertilizer one third at sowing plus two third at mid tillering gave the highest grain yield. This application method gave a yield advantage of 9.96 % over the commonly practiced 1/2 at sowing and 1/2 at mid tillering. It also gave the highest economic return and agronomic Nitrogen Use Efficiency. Keywords: split application timing ,nitrogen fertilizer, nitisols, food barley DOI: 10.7176/JNSR/12-9-02 Publication date: May 31 st 2021

Timing and Splitting of Nitrogen Application to Increase Tef (Eragrostic Tef (Zucc.) Trotter) Yield and Nitrogen Use Efficiency at Central Highlands of Ethiopia

ABSTRACT A field experiment was conducted for three consecutive years (2017 to 2019) to determine the appropriate time of nitrogen (N) fertilizer application during the crop growth cycle for increased tef productivity and nitrogen use efficiency (NUE) at central highlands of Ethiopia. A split-plot experimental design was used with two varieties and eight timings of N application at different growth stages. The results showed that variety and time of N application had a significant effect on growth parameters, NUE traits, yield, and yield components of tef at both locations. Kora variety gave higher growth parameters of tef at both locations and higher yield at Ude. Regarding time of N application, the highest yield was obtained when N was applied 50% at planting +25% at tillering + 12.5% at flag leaf +12.5% at heading, though not significantly different from other split applications at Ude. Split application increased grain yield and NUE traits as compared to full N application at once. However, at Minjar, split application didn’t show any significant difference of grain yield and NUE traits with that of full application. Partial budget analysis at Ude also showed that N application of 50% at planting +25% at tillering + 12.5% at flag leaf +12.5% at heading gave the highest net benefit and MRR. Therefore, four times (50% at planting +25% at tillering + 12.5% at flag leaf +12.5% at heading of split N fertilizer application can be recommended for higher economic yield and NUE of tef at Ude area, but split application is not advantageous at Minjar area.

Comparative analyses of variable and fixed rate irrigation and nitrogen management for maize in different soil types: Part I. Impact on soil-water dynamics and crop evapotranspiration

Understanding the soil-water dynamics and maize evapotranspiration (ETc) under variable rate irrigation (VRI) and variable rate fertigation (VRF) management with respect to soil spatial variability constitutes the basis for developing effective variable rate water and nitrogen management strategies. This long-term research was designed to quantify and compare the soil-water dynamics, including available water (AW), and ETc during vegetative and reproductive growth periods of VRI, fixed rate irrigation (FRI) and no-irrigation (NI) under fixed rate fertigation (FRF), VRF and pre-plant (PP) nitrogen management in three different soil types [Crete silt loam (S1); Hastings silty clay loam (S2) and Hastings silt loam (S3)] with different topography in the same field under the same environmental and management conditions. The research was conducted in the Irmak Research Laboratory in south central Nebraska, U.S.A., in 2015, 2016 and 2017 maize (Zea mays L.) growing seasons under a variable-rate linear move sprinkler irrigation system. No effect of irrigation and nitrogen fertilizer on AW was observed in the vegetative period. Overall, greater AW was observed in S3 as compared with S1 and S2 due to lower elevation. Maize ETc during the vegetative period was significantly (P < 0.05) impacted by soil type in all three years and by nitrogen treatment in two of the three years. The vegetative ETc in S1 was 27 and 19 mm greater than S2 and S3, respectively, for the pooled 2015, 2016 and 2017 data. During the reproductive period, both ETc and AW were impacted by nitrogen and irrigation treatments, but differently in different soil types and years. Average reproductive ETc for FRI and VRI in 2015, 2016 and 2017 was 175 and 178 mm; 294 and 241 mm; 258 and 206 mm, respectively. Averaged across three years, ETc under FRI was significantly (P < 0.05) greater than in VRI; however, in 2015, no significant difference (P > 0.05) in ETc between FRI and VRI was observed in any soil type. Similarly, in 2017, no significant difference in reproductive ETc was observed between VRI and FRI in S1. During reproductive period, averaged across years, soil types and irrigation treatments, the PP nitrogen treatment had greater ETc and lower AW than VRF and FRF. The results indicate that vegetative period ETc was primarily affected by soil type, weather conditions (evaporative demand and soil wetting) and nitrogen fertilizer application timing. The findings of this research showed that soil-water dynamics is a strong function of not only management practices (irrigation and nitrogen treatments), but also soil type, topography and soil physical properties, which all need to be taken into account for effective management of VRI and FRI under VRF, FRF or PP nitrogen management in different soil types. This research quantified the impact of these management practices on soil-water dynamics and ETc which can be used as a guidance.

Impacts of Nitrogen Application on Ammonia Volatilization During Maize Season in Northern China

Ammonia volatilization is one of the major paths of nitrogen (N) loss and may exert a substantial impact on air quality. This study aims to explore the effects of nitrogen (N) fertilizer types, fertilization rate, and application timing and gas collection method on NH3 volatilization during the maize season in Northern China. This study collected the publications on the NH3 volatilization from maize farming which were conducted in Northern China from 1980 to 2018, and undertook a systematic analysis. The study found that with the increase of N rate, the total and net NH3 volatilization at the basal and topdressing fertilization stages increased at exponential and power function, respectively. When the ratio of basal/topdressing N rate was 1/1, the total and net NH3 volatilization during the topdressing stage (58.4% of the whole season emission) was significantly higher than that in the basal fertilization stage (41.6%) (P<0.05). The priming effect first showed a negative effect and then gradually turned into a positive effect with the increase of N rate. Due to the positive priming effect, the net NH3 volatilization, without considering the priming effect, was overestimated under the conventional N application (>297 kg·hm-2). There is a significant difference between the NH3 volatilization measured by the venting method and the sponge absorption method, and the data from the venting method are more stable (P<0.01). Compared with conventional urea, slow-release urea may reduce NH3 volatilization by 20% to 50%. Control fertilizer N rate at the topdressing stage is more efficient in reducing the NH3 volatilization from maize production in Northern China, and the venting method is more suitable for the quantification of NH3 volatilization than the sponge absorption method under a high rate of fertilizer N.

Scheduling of nitrogen fertilizer topdressing during panicle differentiation to improve grain yield of rice with a long growth duration

Topdressing at panicle differentiation (PF) according to soil fertility and regularity of rice nutrient absorption is an important agronomic practice used in cultivation of rice cultivars with a long growth duration. We studied the impacts of timing of nitrogen fertilizer application during PF on photosynthesis and yield-related agronomic traits in ‘Y-Liang-You 900’ and ‘Y-Liang-You 6’, which are representative rice cultivars with a long growth duration. Data for two years showed that timing of topdressing application during PF affected panicles per unit area, percentage grain set, spikelets per panicle, and leaf photosynthetic traits during the grain-filling period. Topdressing at the initial stage of flag-leaf extension resulted in higher grain yield (typically by 10.55–19.95%) than in plants without topdressing. Grain yield was significantly correlated with flag leaf photosynthetic rate and leaf SPAD value (r = 0.5640 and r = 0.5589, respectively; p < 0.01) at an advanced grain-filling stage (30 days after heading). Surprisingly, grain yield was not correlated with carbohydrate remobilization from the stem and sheath. For rice cultivars with a long growth duration, nitrogen-fertilizer topdressing must be applied at the initial stage of flag-leaf extension to delay leaf senescence during the grain-filling stage and realize the enhanced yield potential.

Timing and rate of nitrogen fertilization influence maize yield and nitrogen use efficiency.

Timing and rate of nitrogen (N) fertilizer application can influence maize (Zea mays L.) grain yield, N uptake, and nitrogen use efficiency (NUE) parameters, but results have been inconsistent across the upper Midwest. This study compared single (fall and preplant) and split applications of differing N rates for maize under irrigated conditions on loamy sand at Becker, MN and under rainfed conditions on loam and clay loam soils at Lamberton, MN and Waseca, MN, respectively, in 2014 to 2016. Fall and preplant applications of N were applied at recommended and 125% of recommended rates (RN) according to University of Minnesota guidelines. Split-application treatments included a two-way (Sp, applied at 75% and 100% of RN) and a three-way split (TSp applied at 50%, 75%, and 100% of RN), with the total N rate equally split among application times. At Becker, maize grain yield with TSp was 12.6 to 15.7 Mg ha-1 among years and significantly greater than that with fall or preplant treatments. The TSp treatment also improved agronomic efficiency (AE) and recovery efficiency (RE) by an average of 30% over fall or preplant treatments. At Lamberton, maize grain yield, AE and RE did not differ among treatments. However, TSp75 improved AE by 8.3 kg kg-1 while producing comparable yields to fall and preplant treatments. At Waseca, Sp or TSp improved grain yield and AE compared with fall treatments. These results suggest that split applications of N can increase maize grain yield, AE, and RE on irrigated coarse-textured soils and applying N fertilizer near planting or as a split application can improve N management on non-irrigated clay loam soils.