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The necessity for sustainable agricultural practices has propelled a renewed interest in legumes such as faba bean (Vicia faba L.) as agents to help deliver increased diversity to cropped systems and provide an organic source of nitrogen (N). However, the increased cultivation of faba beans has proven recalcitrant worldwide as a result of low yields. So, it is hoped that increased and more stable yields would improve the commercial success of the crop and so the likelihood of cultivation. Enhancing biological N fixation (BNF) in faba beans holds promise not only to enhance and stabilize yields but also to increase residual N available to subsequent cereal crops grown on the same field. In this review, we cover recent progress in enhancing BNF in faba beans. Specifically, rhizobial inoculation and the optimization of fertilizer input and cropping systems have received the greatest attention in the literature. We also suggest directions for future research on the subject. In the short term, modification of crop management practices such as fertilizer and biochar input may offer the benefits of enhanced BNF. In the long term, natural variation in rhizobial strains and faba bean genotypes can be harnessed. Strategies must be optimized on a local scale to realize the greatest benefits. Future research must measure the most useful parameters and consider the economic cost of strategies alongside the advantages of enhanced BNF. [ABSTRACT FROM AUTHOR]

Abstract The necessity for sustainable agricultural practices has propelled a renewed interest in legumes such as faba bean (Vicia faba L.) as agents to help deliver increased diversity to cropped systems and provide an organic source of nitrogen (N). However, the increased cultivation of faba beans has proven recalcitrant worldwide as a result of low yields. So, it is hoped that increased and more stable yields would improve the commercial success of the crop and so the likelihood of cultivation. Enhancing biological N fixation (BNF) in faba beans holds promise not only to enhance and stabilize yields but also to increase residual N available to subsequent cereal crops grown on the same field. In this review, we cover recent progress in enhancing BNF in faba beans. Specifically, rhizobial inoculation and the optimization of fertilizer input and cropping systems have received the greatest attention in the literature. We also suggest directions for future research on the subject. In the short term, modification of crop management practices such as fertilizer and biochar input may offer the benefits of enhanced BNF. In the long term, natural variation in rhizobial strains and faba bean genotypes can be harnessed. Strategies must be optimized on a local scale to realize the greatest benefits. Future research must measure the most useful parameters and consider the economic cost of strategies alongside the advantages of enhanced BNF.

The relationship between the fate of nitrogen (N) fertilizer and the N application rate in paddy fields in Northeast China is unclear, as is the fate of residual N. To clarify these issues, paddy field and 15N microplot experiments were carried out in 2017 and 2018, with N applications at five levels: 0, 75, 105, 135 and 165 kg N ha−1 (N0, N75, N105, N135 and N165, respectively). 15N-labeled urea was applied to the microplots in 2017, and the same amount of unlabeled urea was applied in 2018. Ammonia (NH3) volatilization, leaching, surface runoff, rice yield, the N contents and 15N abundances of both plants and soil were analyzed. The results indicated a linear platform model for rice yield and the application rate of N fertilizer, and the optimal rate was 135 kg N ha−1. N uptake increased with an increasing N rate, and the recovery efficiency of applied N (REN) values of the difference subtraction method were 45.23 and 56.98% on average in 2017 and 2018, respectively. The REN was the highest at the N rate of 135 kg ha−1 in 2017 and it was insignificantly affected by the N application rate in 2018, while the agronomic efficiency of applied N (AEN) and physiological efficiency of applied N (PEN) decreased significantly when excessive N was applied. N loss through NH3 volatilization, leaching and surface runoff was low in the paddy fields in Northeast China. NH3 volatilization accounted for 0.81 and 2.99% of the total N application in 2017 and 2018, respectively. On average, the leaching and surface runoff rates were 4.45% and less than 1.05%, respectively, but the apparent denitrification loss was approximately 42.63%. The residual N fertilizer in the soil layer (0–40 cm) was 18.37–31.81 kg N ha−1 in 2017, and the residual rate was 19.28–24.50%. Residual 15N from fertilizer in the soil increased significantly with increasing N fertilizer, which was mainly concentrated in the 0–10 cm soil layer, accounting for 58.45–83.54% of the total residual N, and decreased with increasing depth. While the ratio of residual N in the 0–10 cm soil layer to that in the 0–40 cm soil layer was decreased with increasing N application. Furthermore, of the residual N, approximately 5.4% was taken up on average in the following season and 50.2% was lost, but 44.4% remained in the soil. Hence, the amount of applied N fertilizer should be reduced appropriately due to the high residual N in paddy fields in Northeast China. The appropriate N fertilizer rate in the northern fields in China was determined to be 105–135 kg N ha−1 in order to achieve a balance between rice yield and high N fertilizer uptake.

Soil residual N is a potential factor threatening the environment, but it is also an N fertilizer resource. Few studies have evaluated the fate of soil residual N under agronomic practice. The objective of this study was to investigate the distribution of residual N and its possible influencing factors with different irrigation regimes. Under three N residual situations created by the previous season using the 15N labeled urea, we employed lettuce as the plant material and three lower limits of drip irrigation including 75% (DR1), 65% (DR2), and 55% (DR3) accounting for the field water capacity as experimental treatments. A furrow irrigation treatment (FI) with the same irrigation regime as DR2 was used as control. Results showed that 2.1–4.8% of the residual 15N from the previous season was absorbed by the succeeding lettuce, 78.0–84.4% was still remained in the 0–80 cm soil, and 10.9–20.0% was unaccounted for. After harvest of succeeding lettuces, the soil residual 15N mainly existed in the mineral form. Moreover, the lettuce reuse efficiency for15N was positively correlated with the total residual 15N amount (p < 0.01) and the mineral 15N amount (p < 0.01). The overall results indicated that an appropriate irrigation regime (DR2) was conducive to promoting absorption of residual N by succeeding crop. [ABSTRACT FROM AUTHOR]

Nitrogen fertilizer is essential for the yield and quality of flue-cured tobacco. Honghuadajinyuan (i.e. Hongda) is a special flue-cured tobacco variety in Yunnan, which differs in nitrogen application rates from other varieties. In 2016 and 2017, different nitrogen application rates were established in Yunnan to compare, with other varieties, Hongda's agronomic, economic, chemical indicators and soil residual nitrogen. As nitrogen fertilizer rate increased, the ratio of fresh weight to dry weight (RFD) and the proportions of inferior tobacco (PIT) initially decreased and then increased in contrast to the proportions of superior tobacco (PST) and average price. Total sugar and reducing sugar contents in flue-cured tobacco leaves decreased as nitrogen fertilizer rate increased, while total nitrogen, nicotine, and protein contents increased. The highest sensory evaluation scores were obtained with 45 and 60 kg N ha−1. Soil nitrate contents increased with increasing nitrogen fertilizer rate and significantly increased when nitrogen application rate exceeded 60 kg N ha−1. A quadratic model was suitable for Hongda's response to nitrogen fertilizer rate and 60 kg N ha−1 can meet the needs of the growth of this flue-cured tobacco variety. Abbreviations: Hongda: Honghuadajinyuan; RFD: ratio of fresh to dry weight; PIT: proportion of inferior tobacco; PMT: proportion of medium tobacco; PST: proportion of superior tobacco; SPAD: soil and plant analyzer development. [ABSTRACT FROM AUTHOR]

Partial root-zone irrigation (PRI) has been practiced worldwide, but little information is available on nitrogen (N) supply methods influence on fate of applied N fertilizer for crop production under PRI. A field experiment was conducted to investigate effect of N supply methods on the uptake, residual, and loss of applied N fertilizer in maize (Zea mays L.) under alternate PRI at Wuwei, northwest China in 2014. 15N-labeled urea was used as N fertilizer. Two irrigation methods included alternate furrow irrigation (AI) and conventional furrow irrigation (CI). Two N fertilizer supply methods included conventional N supply (CN) and alternate N supply (AN), were applied in combination with each irrigation method. Grain yield, root length density (RLD), N uptake by maize at the maturity stage, and atom % of 15N excess, residual 15N and residual NO3-N in the 0-100 cm soil layer after maize harvest were determined. Results shown that compared to CI coupled with CN, AI coupled with AN or CN significantly increased the grain yield, harvest index, RLD, N uptake by maize, 15N accumulation in grain, atom % of 15N excess in the 0-60 cm soil layer, the residual 15N and 15N uptake rates; but significantly decreased the residual NO3-N in the 0-100 cm soil layers and 15N loss rate. Moreover, the synchronized rather than separation supply of N fertilizer and water enhanced the most above parameters under AI. 15N uptake rate was positively correlated with RLD in the 0-40 cm soil layer, suggesting that the enhanced RLD contributed to the improved 15N uptake rate. Therefore, alternate furrow irrigation coupled with conventional or alternate nitrogen supply (synchronized supply of N fertilizer and water) could help improve 15N uptake rate and reduce the 15N loss rate. [ABSTRACT FROM AUTHOR]

Nitrogen management is a challenging task and several methods individually and in combination are in use to manage, nevertheless, nitrogen use efficiency has not been ameliorated to a level as predicted by the researchers while developing nitrogen management tools and methods. The experiments were carried out from 2012 to 2014 on meadow-chestnut heavy loamy soil at "Bikesha" farm in Tarumovsky district of the Republic of Dagestan, Russia to study the influence of previous crops which include winter wheat for green manure and fodder production, row crops and alfalfa on the winter wheat. Six treatments used in the experiment were winter wheat-three years without rotation, winter wheat-two years without rotation + natural phytocenosis for green fertilizer, winter wheat-two years without rotation + natural phytocenosis for fodder production, corn for grain, sunflower for seeds and alfalfa for hay. Nitrogen concentration in the phytomass during harvesting of precursors was determined before ploughing and mowing the natural phytocenosis for fodder production. The results showed that the maximum content of plant material in soil (25.82 t/ha), the highest nitrogen concentration (2.18 to 3.32 %) and higher productivity of winter wheat (4.67 t/ha) were demonstrated when the previous crop was alfalfa and natural phytocenosis. These findings can be used to design crop rotations enriched with the main food crop of up to 80 to 100% without compromising crop yields and soil fertility in small farms, which have a small set of crops, as well as insufficient material and technical resources. [ABSTRACT FROM AUTHOR]

The fate of residual nitrogen (N) in specific soil layers under partial root‐zone irrigation (PRI) and fertilized with different N forms was studied using a soil column experiment with 15N‐labelled N (K15NO3) applied to 110‐cm‐deep soil layers. We found that alternate PRI (APRI) saved 34.3% more irrigation water but only decreased yield by an average of 6.2%, whereas fixed PRI (FPRI) and deficit irrigation (DI) reduced fruit yield by an average of 25.5 and 35.0%, respectively, compared to conventional sufficient irrigation (CI). Using the same irrigation mode, nitrate‐N application significantly promoted 15N‐utilization by the tomato fruit and crops for all irrigation modes. Compared to ammonium‐N application, nitrate‐N application increased the recovery rate of 15N‐labelled N in plants by 30.6% under CI, 14.3% under APRI, 22.8% under FPRI, and 10.6% under DI. The 15N accumulation peak was found at a depth of 40–60 cm, corresponding to an upward 15N migration distance of 65 cm for all treatments. However, a significant difference in the amount of residual N in the crop root zone (0–100 cm) was observed between CI and the other irrigation methods. Highlights: Effects of PRI on the fate of residual nitrate studied with the15N tracer technique and simulated soil column.APRI could save 34.3% irrigation water without significant effects on tomato yield.Nitrate‐N application significantly promoted the growth of tomato.The residual nitrate in deep subsoil mainly moved upward under all irrigation modes. [ABSTRACT FROM AUTHOR]

Non-optimal application of nitrogen (N) fertilizer in cotton (Gossypium hirsutum L.) production systems often results from a producer’s uncertainty in predicting the N rate that ensures maximum economic return. Residual soil nitrate-N (NO3-N) is also often unaccounted for in fertilizer management decisions. In this study, the lint yield and profitability of two cotton cultivars (FiberMax FM 958 and Deltapine DP 1646 B2XF) were compared across five N fertilizer treatments [0 kg ha−1 (control), 45 kg ha−1 (N-45), 90 kg ha−1 (N-90), 135 kg ha−1 (N-135), 180 kg ha−1 (N-180)] from 2018 to 2020. For both cultivars, additional N fertilizer on top of the control treatment did not increase the lint yield of cotton. For each year, both control and N-45 treatments resulted in the greatest revenue above variable costs (RAVC) values for all cultivars. The improved N partitioning efficiency in newer cultivars and the high levels of residual soil NO3-N allowed sustained plant growth and yield even with reduced N application. Overall, the results show the advantage of reducing N inputs in residual N-rich soils to maintain yield and increase profits. These findings are important in promoting more sustainable agricultural systems through reduced chemical inputs and maintained soil health.

Highlights • The 15N tracer technique and simulated soil column method were used to study the effects of APRI on the movement and utilization of residual nitrate. • APRI could save 38.8% irrigation water without significant effects on tomato yield. • APRI improved the absorption of residual nitrate and facilitated the transfer of nitrogen from the stems and leaves to the fruits. • Compared to residual nitrate in the upper layer, nitrate in the lower layer showed less potential for absorption and a diminished leaching distance. • Under APRI, the 15N loss rate significantly decreased, but the utilization did not significantly decrease. Abstract Alternate partial root-zone irrigation (APRI) can greatly affect water conservation and yield stabilization via its physiological regulation of plants. However, most studies have not distinguished the fate of residual nitrogen in specific soil layers, and little attention has been paid to the utilization and fate of residual nitrogen in different soil layers under APRI. The aim of this study is to evaluate the fate of nitrate accumulated in different soil profiles and its potential for utilization by crops under APRI. The 15N tracer technique and simulated soil column method were used to study the effects of APRI on the movement and utilization of residual nitrate. The results showed that, compared to conventional irrigation, APRI could save 38.8% irrigation water without significant effects on tomato yield, even though the total plant biomass significantly decreased. APRI improved the absorption of residual nitrate and facilitated the transfer of nitrogen from the stems and leaves to the fruits. Compared to residual nitrate (labeled by 15N) in the upper layer (10–20 cm), nitrate in the lower layer (40–50 cm) showed less potential for absorption by tomato plants and a diminished leaching distance, corresponding to a significantly increase loss (rate). Under APRI, the 15N loss rate significantly decreased, but the utilization did not significantly decrease, compared to conventional irrigation. Moreover, APRI promoted root development, especially fine root growth, and reduced the leaching of residual nitrate in different soil layers. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agronomica Sinica is the property of Crop Science Society of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Crop production alters nitrogen balance in double cropping of winter wheat-summer maize in grain nitrogen content, soil nitrogen pool and nitrogen loss, ultimately affecting nitrogen use efficiency and environmental health. In comparison to the information on crop responses only limited knowledge exists on the response of nitrogen balance to integrated agronomic practices management (IAPM, defined as a comprehensive management framework consisted of tillage method, plant density, seeding and harvest dates, and fertilizer application) under field. Planting pattern will affect crop production and environmental costs. And how the nitrogen balance change under IAPM? In order to answer this question, four treatments (T1, T2, T3 and T4) were conducted on double cropping of winter wheat-summer maize for 4 years in North China Plain. Annual grain yield of T2, T3, and T4 was 22.0%, 51.2%, and 33.3%, respectively, higher than T1. And single grain yield of winter wheat or summer maize had the same trend as the annual grain yield. Dry matter accumulation of T2, T3, and T4 in summer maize season were 8.3%, 42.0%, and 23.0%, and those in winter wheat season were 3.9%, 25.7%, and 12.1%, respectively, higher than T1 at harvest. The grain yield of T4 was lower than that of T3 but higher than that of T1 and T2, and net profit and nitrogen use efficiency of T4 were higher than that of T3. Meanwhile the highest current and residual nitrogen recovery efficiency ( C RE N and RE RE N ) were obtained by T4 treatment during the study period. The soil nitrogen content in 0–90 depth (SN), grain nitrogen content (GN), nitrogen apparent recovery efficiency (ARE N ) and fertilizer nitrogen loss (FNL) were measured for nitrogen balance. T4 treatment promoted nitrogen balance as higher GN, higher ARE N and lower FNL. The GN kept stable and FNL was increasing slowly in all treatments, which mean the contribution to soil nitrogen pool was decreasing with experimental years. The grain yield for T4 treatment of winter wheat, summer maize and annual increased by 36.4%, 31.3% and 33.3% averagely in the past 4 years, compared with T1 treatment. While maintaining crop production, T4 treatment made an important contribution to promoting nitrogen use efficiency, improving the situation of nitrogen balance, and reducing nitrogen loss about 39.1–54.4%, compared with other treatments. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Switchgrass, Panicum virgatum L., grown for biomass has been extensively researched where the annual precipitation >760 mm and the climate varies from humid to moist-subhumid. Research is needed for areas that receive <700 mm of precipitation, where the climate varies from dry-subhumid to semiarid. The objectives were to determine (1) the effect of nitrogen fertilization on biomass production, (2) the effect of residual nitrogen on biomass production, (3) the nitrogen yield from harvested biomass, and (4) the concentration of soil organic carbon (SOC) from switchgrass plots. Plots were fertilized annually with nitrogen at the rates of 0, 40, 80, and 120 kg ha from 2008 to 2011 and unfertilized from 2012 to 2015. The biomass yield varied with N rate × production year interactions ( P < 0.05), and biomass yield as a function of N rate was either linear or curvilinear depending upon production year. When fertilized, the biomass yield averaged 4.4, 9.4, 11.6, and 13.2 ± 0.4 Mg ha for the 0, 40, 80, and 120 kg ha N rates, respectively. Residual nitrogen sustained high biomass yields for 1 year after fertilization ceased. The nitrogen harvested in biomass varied with N rate × production year interactions ( P < 0.05), and the harvested nitrogen yield as a function of N rate was linear each year. Fertilization increased the concentration of SOC an average of 1.0 ± 0.2 mg g of soil. The data suggest that producers could occasionally skip a year of nitrogen fertilization without detrimentally impacting the production of switchgrass biomass. [ABSTRACT FROM AUTHOR]

Studies were conducted to evaluate response of dryland corn (Zea mays L.) along the upper Texas Gulf Coast to residual soil nitrate-nitrogen (NO3-N) measured to depths of 15, 30, and 61 cm. Residual soil NO3-N levels ranged from 3.4 to 31.6, 7.8 to 49.3, and 9.0 to 71.7 kg ha−1, respectively, in 0 to 15, 15 to 30, and 30 to 61 cm depth increments, with cumulative NO3-N ranging from 23.5 to 114.5 kg ha−1 across sites-years. Where N fertilizer was reduced due to N crediting, yields and bushel weights at all 13 site-years showed no difference from those receiving full recommended N rates. A yield response to any level of added fertilizer N above the control was observed for only 6 of 13 site-years. These results indicate a high potential for success in crediting carryover soil NO3-N to 61 cm as a means of reducing applied nitrogen fertilizer rates. [ABSTRACT FROM AUTHOR]

The use of high rates of nitrogen (N) fertilizers in irrigated potato crops may increase the risk of N losses to the environment. The aim of this study was to evaluate the effect of N rate (250,150, 100 and 0 kg N ha-1), source (urea and treated urea nBTPT), and timing (at planting and tuber initiation) on the N mass balance in potato crop of Villa Dolores, Córdoba. Nitrogen losses were estimated by quantifying N inputs (initial N, mineralized soil N and N fertilizer) and N outputs (N accumulated in tubers, in straw and residual soil N) in two production plots. No differences were determined between nBTPT and urea for any of the evaluated variables. Tuber yield was greater using 250 kg N ha-1 or with 150 and 100 kg N ha-1 at the start of tuberization. The tuber yield obtained by fractional fertilization of 100 kg N ha-1 was lower compared to this same rate applied at the start of tuberization. Estimated N losses ranged from 29 to 235 kg ha-1, and were significant even in the control treatment. Most of these losses were caused by nitrate leaching in the early stages of the season. [ABSTRACT FROM AUTHOR]

Background and aims The main objectives of this paper were to investigate the absorption and utilization of nitrogen applied at the panicle stage in rice for promoting and protecting spikelet and the effect of residual nitrogen on the utilization of nitrogen in the succeeding wheat crop in the rotation system. Methods A field experiment was combined with a mini-plot experiment with 15 N labelled urea applied at the panicle stage in rice. The experiments included three nutrient management treatments: F, S1 and S2. 126 kg N ha −1 , 120 kg N ha −1 , 72 kg N ha −1 labeled with 30 atom% excess 15 N were applied in rice, respectively. Results (1) Compare to conventional fertilizer management (F), the optimized fertilizer management (S1&S2) reduced the amount of nitrogen applications, whereas the rice and wheat yield did not decrease, and nitrogen use efficiency was improved. (2) At rice harvest, 4.7–10.7% of the fertilizer 15 N was found in the 0–20 cm profile. The fertilizer 15 N absorbed by the wheat during the period from jointing to heading accounted for 37.0%-51.1% of the total 15 N absorbed. (3) The sum of the ratio of nitrogen absorption from the rice panicle fertilizer applied to the crops (rice and wheat) and ratio of soil residue nitrogen in the wheat field were ordered S2 > S1 > F. Conclusion The optimized fertilization management reduced the loss of the rice nitrogen in the rice–wheat rotation system through improved recycling of rice panicle nitrogen applied in the crop-soil system. [ABSTRACT FROM AUTHOR]

Nutrients and nitrate move to the boundary of the wetted zone under drip-tape irrigation (DTI) of row crops, so irrigation depth, wetted width, and irrigation frequency are the most important factors in managing the wetting front and keeping N in the root zone. Many farmers in arid regions who have changed their irrigation systems to DTI, but they are still applying N in two splits as they are used for surface and sprinkler irrigation. Crop models can be used to optimize the timing and amount of nitrogen fertilizer applied to minimize both N leaching and the amount of N remaining in the soil after harvest. The objectives of this study were to calibrate the Cropping System Model (CSM)-CERES-Maize for two maize hybrids and to evaluate the model under DTI with two different soil wetting widths. The single cross Hybrid 704 (SC704) grown in two experimental fields (Exp-1 and Exp-2) and the single cross Hybrid 606 (SC606) grown in one experimental field and two farmer fields (Exp-3, Ff-1 and Ff-2) were evaluated during three years (2016, 2017 and 2019). Plant traits including leaf area index (LAI), total biomass (TB), soil moisture (SM), nitrogen uptake (NU) and water productivity (WP) were measured. Soil NO 3 -N was measured at three distances from the planting row and three soil depths in Exp-1 and Exp-3 during two maize growth stages. The fraction of the wetted width (fw) along drip-tape was 70% in Exp-1% and 100% in Exp-3 (referred to as fw-70 and fw-100, respectively). The results showed good performance of the model for simulating TB and LAI with NRMSE < 21.9% for the two hybrids in the applied N fertilizer treatments. The accuracy of the simulation of SM and WP in fw-100 was better than that of fw-70. Simulated NO 3 -N followed the observed trend for fw-100, while model performance varied for the different irrigation and N levels in fw-70. Model accuracy for soil NO 3 -N prediction decreased for the high N fertilizer application under deficit irrigation management. These differences were related to the wetting pattern volume, the distribution of N in the soil profile, and accumulation of soil N under DTI. Overall, the model can simulate TB and NU with high accuracy, SM with good accuracy, and soil NO 3 -N with an acceptable accuracy under DTI. The accuracy of the model was also higher for the unlimited wetting width, as compared to the limited one. This study showed that the CSM-CERES-Maize model can be used for evaluation of nitrogen management practices for drip irrigated maize grown under arid conditions. [Display omitted] • Model prediction for soil NO 3 -N and N uptake were affected by fraction of soil wetted width under DTI. • Model prediction was good for total biomass and N uptake in different wetting width via DTI. • Model accuracy for soil NO 3 -N prediction decreased in high N fertilizer application under deficit irrigation management. • Model accuracy for soil nitrogen was higher for 100% wetting width under DTI. • The soil nitrogen simulation accuracy was affected by nitrogen level. [ABSTRACT FROM AUTHOR]

A field experiment with wheat (Triticum aestivumL.) was established over two growing seasons where farmyard manure and sewage sludge, along with conventional fertilizer, were added to soil. We found that ammonium N was at greater concentrations in the organic amendments treatments, indicating more beneficial dynamics (i.e., it can be taken up by plants for a greater amount of time) and thus a longer lasting effect as a nutrient for the test crop. We found that nitrogen (N), phosphorus (P), and potassium (K) uptake increased with added organic amendments. This means that when organic matter along with nutrients are added to soil, productivity may increase beyond preset targets because soil conditions greatly improve, not only chemically but also physically. Nitrates left over at the end of the growing season (residual N) were greater in the high sewage sludge and manure treatments, but not proportionally. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effect of frequent and periodic applications of sewage sludge to the soil, on corn productivity. The experiment was carried out as part of an experiment that has been underway since 1999, using two types of sludge. One came from the Barueri Sewage Treatment Station (BS, which receives both household and industrial sludge) and the other came from the Franca Sewage Treatment Station (FS, which receives only household sludge). The Barueri sludge was applied from 1999 up to the agricultural year of 2003/2004. With the exception of the agricultural years of 2004/2005 and 2005/2006, the Franca sludge was applied up to 2008/2009. All the applications were made in November, with the exception of the first one which was made in April 1999. After harvesting the corn, the soil remained fallow until the next cultivation. The experiment was set up as a completely randomized block design with three replications and the following treatments: control without chemical fertilization or sludge application, mineral fertilization, and dose 1 and dose 2 of sludge (Franca and Barueri). The sludges were applied individually. Dose 1 was calculated by considering the recommended N application for corn. Dose 2 was twice dose 1. It was evident from this work that the successive application of sludge to the soil in doses sufficient to reach the productivity desired with the use of nitrogen fertilizers could cause environmental problems due to N losses to the environment and that the residual and cumulative effects should be considered when calculating the application of sludge to soil. [ABSTRACT FROM AUTHOR]

When carrots (Daucus carota L.) are mechanically harvested, sufficient nitrogen (N) must be balanced between the roots and carrot tops; weak tops reduce yield. A 2-year study was conducted in Montcalm County, Michigan, where four replications of four N treatments (45, 90, 135, and 180 kg ha−1), were arranged in a randomized complete block design. Results showed the importance of determining pre-existing N sources, in as much as the deep taproot of carrot accessed unmeasured N in the subsoil and nitrate concentrations in irrigation water added N. The greatest yield occurred at 153–189 kg ha−1available N while tops continued to take up N through 200–232 kg ha−1. When the last N application was made less than 35 days before harvest, the rate of N uptake exceeded dry-matter accumulation rate. [ABSTRACT FROM PUBLISHER]

Proper management of manure nitrogen (N) requires the ability to match the rate and extent of manure N availability with crop needs. This includes recognizing the potential importance of N contributions from residual manure N that accumulates with repeated applications. Nitrogen availability relative to barley needs was assessed in plots with 13-16 years continuous histories of contrasting manure-based (solid-bedded beef) and fertilizer-based soil treatments in the Maine Potato Ecosystem Project. Soil and barley samples were collected every 7-14 days during 2003-2005, and once in 2006. Barley dry matter and N content were equivalent between the two systems. In the manure-based system, temporal patterns of N availability were more synchronous with early season crop needs than in the fertilizer-based system, but continued mineralization after harvest was also observed. In 2004-2006, samples were collected from subplots where manure/fertilizer was withheld to estimate the proportion of available N originating from current versus previous manure applications. Apparent N recovery of current years' applications of manure organic N was 8-11% and less than predicted by a standard decay series model for beef manure (25%), highlighting the need to adjust manure N credits for crops with shorter growing seasons and lower N uptake capacities than corn. The relative contribution of residual manure N to total manure N uptake was greater than predicted from the decay series model, providing support for a residual N effect from repeated manure applications that is not accounted for in standard manure recommendations. [ABSTRACT FROM AUTHOR]

In recent decades, continuous increase of N fertilizer inputs made significant contributions to the wheat production increase in the Huang-Huai-Hai Plain, the largest wheat producing region of China. However, gradually the use efficiency of N fertilizer decreased, and the increasing N rate led to a series of environment problems. A better quantitative understanding of the fates of basal N and topdressing N under water-nitrogen interactions in a wheat-soil system is essential to increase yield and reduce environmental impacts. We conducted two-year wheat experiments combining field plots and micro-plots with the l5N-labeled method under two irrigation regimens (rainfall, irrigation in jointing and anthesis) and three N rates (0, 180, and 270 kg ha−1). The results showed that 54.9%− 70.4% of total wheat N accumulation was from soil native N, while 29.6%− 45.1% was from fertilizer N. Irrigation at joint and anthesis has increased wheat N accumulation more from fertilizer N than from soil native N. Compared with rainfed condition, irrigation significantly increased plant NNI at booting and anthesis. The contribution of pre-anthesis N translocation to grain N was 80.6%− 86.0%, and increased with increasing total N rate, but decreased with irrigation. The fertilizer N recovery rate increased as N rate and irrigation increased, and more N recovery occurred during jointing to anthesis period (13.1%−31.3%) than anthesis to maturity period (5.7%−10.8%) and sowing to jointing period (8.4%−8.9%). Residual fertilizer N in soil accounted for 24.5%− 38.6% and decreased with increasing total N rate and irrigation. 23.6%− 32.7% of fertilizer N was lost into the environment, and it decreased with increasing irrigation, but wasn't affected by total N rate. The recovery and residual for topdressing N were higher than those for basal N, whereas loss was lower. Moreover, the loss of basal N mainly occurred before jointing, and the loss of topdressing N mainly occurred from jointing to anthesis and contributed more to total N loss. These results indicated that the current wheat-soil system in Huang-Huai-Hai Plain has substantial potential to coordinate the synchronization of N demand and N supply, and finally reduce N loss. Also, this would provide critical insights to construct general crop N management models for precise N management. • Irrigation increased NUE due to its higher promoting effects for fertilizer N than soil native N. • Fertilizer N recovery increased as N rate and irrigation increased, while N residual was the opposite. • The N recovery and residual were higher for topdressing N than basal N, whereas N loss was lower. • Basal N loss mainly occurred before jointing and contributed more to total N loss than topdressing N. • Fertilizer N loss decreased with increasing irrigation, but wasn't affected by N rate. [ABSTRACT FROM AUTHOR]

Abstract: Experiments were conducted in lysimeters with sandy soil under an automatic rain-out shelter to study the effects of subsurface drip irrigation treatments, full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD), on nitrogen (N) dynamics in the soil-plant system of potatoes. In 2005, FI and PRD2 were investigated, where FI plants received 100% of evaporative demands, while PRD2 plants received 70% water of FI at each irrigation event after tuber initiation. In 2006, besides FI and PRD2 treatments, DI and PRD1 receiving 70% water of FI during the whole season were also studied. Crop N uptake and residual NH 4-N and NO3-N to a depth of 0–50cm, at 10cm intervals were analyzed. For both years, the PRD2 treatment resulted in 30% water saving and maintained yield as compared with the FI treatment, while when investigated in 2006 only, DI and PRD1 treatments resulted in significant (P <0.05) yield reductions. In 2005, the soil residual N content at harvest was significantly 29% lower with PRD2 than for FI in the whole root zone; and leaf N concentration for PRD2 was significantly higher than for FI. In 2006, soil residual N content at harvest was 33% lower with PRD2 than for FI, which was not significant however. In the late season, reflectance vegetation index and leaf area index for the water saving treatments were higher than for the FI treatment. For both years the PRD2 treatment had the lowest residual N content in the root zone. We conclude that: (1) of the investigated water saving irrigation strategies (PRD1 PRD2, DI) PRD imposed just after tuber initiation until maturity (PRD2) was the only strategy able to maintain yield; thus, soil drying induced by PRD or DI treatments should be avoided during early growth stages; (2) the PRD and DI treatments improved soil nitrogen availability late in the growing season maintaining top ‘greenness’ to a greater extent, as compared with FI. [Copyright &y& Elsevier]

Non-optimal application of nitrogen (N) fertilizer in cotton (Gossypium hirsutum L.) production systems often results from a producer's uncertainty in predicting the N rate that ensures maximum economic return. Residual soil nitrate-N (NO3-N) is also often unaccounted for in fertilizer management decisions. In this study, the lint yield and profitability of two cotton cultivars (FiberMax FM 958 and Deltapine DP 1646 B2XF) were compared across five N fertilizer treatments [0 kg ha−1 (control), 45 kg ha−1 (N-45), 90 kg ha−1 (N-90), 135 kg ha−1 (N-135), 180 kg ha−1 (N-180)] from 2018 to 2020. For both cultivars, additional N fertilizer on top of the control treatment did not increase the lint yield of cotton. For each year, both control and N-45 treatments resulted in the greatest revenue above variable costs (RAVC) values for all cultivars. The improved N partitioning efficiency in newer cultivars and the high levels of residual soil NO3-N allowed sustained plant growth and yield even with reduced N application. Overall, the results show the advantage of reducing N inputs in residual N-rich soils to maintain yield and increase profits. These findings are important in promoting more sustainable agricultural systems through reduced chemical inputs and maintained soil health. [ABSTRACT FROM AUTHOR]

The recovery of soil mineral nitrogen (N) by crops, and its subsequent utilisation for dry matter (DM) production may be increased when the application of N is postponed until after crop emergence. The significance of this strategy for silage maize was studied in nine field experiments on Dutch sandy soils from 1983 to 1988. In five experiments the effect of slurry applied before planting at a rate of circa 66 m3 ha-1, was compared to the effect of a similar rate of which half was applied before planting and half at the 4–6 leaf stage. In the 4-6 leaf stage slurry was either injected or banded. In four other experiments the effect of mineral fertilizer-N splitting was studied. In these experiments, 30 m3 ha-1 cattle slurry, applied before planting, was supplemented with mineral fertilizer-N at rates ranging from 40 to 160 kg ha-1, either fully applied before crop emergence or split. When split, 40 kg ha-1 of the mineral fertilizer-N rate was banded at the 4–6 leaf stage. According to balance sheet calculations, substantial losses of slurry N and mineral fertilizer-N occurred during the growing season. Losses were compensated for, however, by apparent mineralization, ranging from 0.34 to 0.77 kg N ha-1 day-1. Split applications of cattle slurry had a significant positive effect on the DM yield in two out of five experiments compared to the conventional non-split application, but only when the post-emergence slurry application was banded which is no longer in accordance with present legislation. Split applications of mineral fertilizer-N had a significant positive effect in one experiment where rainfall was excessive but not in the others. The results provide insufficient evidence to recommend farmers to split applications. Soil mineral N sampling at the 4–6 leaf stage should hence be considered a control on the appropriateness of early N applications after exceptional weather conditions rather than a routine observation on which the post-emergence N dressing is to be based in a deliberate splitting strategy. Our data suggest that the financial return of a 40 kg ha-1 supplementation with mineral fertilizer-N, was questionable when more than 175 kg N ha-1 were found in the upper 0.6 m soil layer at the 4–6 leaf stage. [ABSTRACT FROM AUTHOR]

• Cover crops reduced nitrate in the upper 60–120 cm soil depths in the fall. • Winter cereal monoculture covers resulted in low spring topsoil and subsoil nitrate. • Covers with radish or legume resulted in low subsoil but high topsoil nitrate. • Winter cereal monoculture covers immobilized N and restrained spring corn growth. • Fertilized corn yielded more after radish or no cover than after monoculture cereal. In the mid-Atlantic USA region, nitrogen uptake by crops ceases about four weeks prior to harvest maturity, leaving substantial mineral N in the soil profile, which is prone to leach during the winter. Deep-rooted cover crops planted by early-September can potentially take up residual N and recycle some of it for following cash crops. We performed experiments on 19 minimum-tillage, grain farms investigating four unfertilized cover crop systems (forage radish (Raphanus sativus L.), winter cereal or grass, forage radish + winter cereal + crimson clover (Trifolium incarnatum L.), and a no cover crop control). We measured cover crop biomass, N uptake, and inorganic N distribution within the upper 210 cm of soil in late-fall and early-spring, and the following corn (Zea mays L.) crop's growth and yield. In late-fall, radish reduced soil NO 3 in the upper 90 cm by 66 %, while winter cereal or mix cover crops reduced NO 3 in the upper 60 cm by 67 % and 56 %, respectively, compared to a no cover crop control. In the spring, the radish and mix cover crops resulted in comparable nitrate levels to the no cover crop control in the topsoil layer (> 30 kg ha−1) and less nitrate than the no cover crop control in subsoil layers. The winter cereal cover crop had low nitrate levels in the topsoil (∼20 kg ha−1) layer and subsoil layers. The biomass and N content of corn seedling (5 leaf) were influenced by the previous cover crop treatment in the order radish (4.0 g biomass plant−1) > mix (3.0 g biomass plant−1) = control (3.5 g biomass plant−1) > winter cereal (2.4 g biomass plant−1). At the farmers' standard N fertilizer application rate, corn yield following radish was higher than following the winter cereal or mixed species cover crop but corn yield following radish was not different than following no cover crop. Corn yield following the winter cereal cover crop was lower than following no cover crop. Cover crops can be fit within the framework of existing cropping systems to scavenge residual N, therein reducing subsoil inorganic N. Radish and mixed species cover crops can be used prior to corn without reducing the overall short-term N use efficiency of the cropping system. [ABSTRACT FROM AUTHOR]

• Residual nitrogen in cellulosics comes from bound amines from processing or washing. • The bound amines originate, e.g., from cellulose solvents, swelling agents or enzymes. • 2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ) is a cellulose key chromophore formed upon aging. • DHBQ has a high affinity to amines and binds them covalently. • DHBQ is a major cause of nitrogen fixation in aged cellulosics. • There is a direct, linear relationship between formed DHBQ and bound amine traces. Cellulosic material is capable of permanently retaining nitrogen compounds (mostly having amino functions), which is reflected in a residual nitrogen content (in the low per mille range to the low percent range) of some pulps and certain lab samples. Merely adsorptively bound compounds can be removed by mild acidic washing, but part of the nitrogen seems to be resistant and very tightly bound, and thus not accessible for removal by washing. Tertiary and aromatic amines are not retained in this way, but only primary and secondary amines. There is only a weak correlation between the "firmly bound nitrogen" and the carbonyl content in cellulosics (because of oxidative damage), so that possible aminal, Schiff base and enamine structures can hardly be relevant as major nitrogen sources. However, there is a very good linear correlation between the ISO brightness (chromophore content) in aged pulps and the residual nitrogen content. In particular the concentration of the cellulosic key chromophore 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) determines the permanent N -binding capacity of the pulp. DHBQ reacts very readily with primary and secondary amines under ambient conditions to 2,5-diamino-substituted [1,4]-benzoquinones, which have very low solubility (because of zwitterionic resonance contributions) and thus remain on/in the pulp. Examples of nitrogen fixation in pulps are the binding of piperidine (a common amine catalyst in derivatization reactions), amine degradation products of the cellulose solvent NMMO, dimethylamine in materials processed from the cellulose solvent DMAc/LiCl, imidazole (a degradation product of 1-alkyl-3-methylimidazolium ionic liquids), and of amino groups in proteins after enzymatic treatment. The nature of the respective DHBQ-amine addition compound has been verified by complete structure determination. [ABSTRACT FROM AUTHOR]