Long-term nitrogen balance for pearl millet (Pennisetum glaucum L.) in an acid sandy soil of Niger

On acid sandy soils of Niger (West Africa) fertilizer N recovery by pearl millet (Pennisetum glaucum L.) is often more than 100 per cent in years with normal or above average rainfall. Biological nitrogen fixation (BNF) by N₂-fixing bacteria may contribute to the N supply in pearl millet cropping systems. For a long-term field experiment comprising treatments with and without mineral fertilizer (F) and with and without crop residue application (CR) a N balance sheet was calculated over a period of six years (1983-1988). After six years of successive millet cropping total N uptake (36-77 kg N ha^?1 yr^?1) was distinctly higher than the amount of fertilizer N applied (30 kg N ha^?1 yr^?1). The atmospheric input of NH₄-N and NO₃-N in the rainwater was about 2 kg N ha_?1 yr^?1, 70 % in the form of NH₄-N. Gaseous NH₃ losses from urea (broadcast, incorporated) were estimated from other experiments to amount to 36 % of the fertilizer N applied. Nitrogen losses by leaching (15 to > 25 kg N ha^?1 yr^?1) were dependent on the treatment and on the quantity and distribution of single rainfall events (>50 mm). Decline in total soil N content (0-60 cm) ranged from 15 to 48 kg N ha^?1 yr^?1. The long-term N balance (1983-1988) indicated an annual net gain between 6 (+CR-F) and 13 (+CR+F) kg N ha^?1 yr^?1. For the control (-CR-F) the long-term N balance was negative (10 kg N ha^?1 yr^?1). In the treatment with crop residues only, the N balance was mainly determined by leaching losses, whereas in treatments with mineral fertilizer application the N balance depended primarily on N removal by the millet crop. The annual net gain in the N balance increased from 7 kg ha^?1 with mineral fertilizer to 13 kg ha^?1 in the combination mineral fertilizer plus crop residues. In both the rhizosphere and the bulk soil (0-15 cm), between 9 and 45% of the total bacterial population were N₂-fixing (diazotrophic) bacteria. The increased N gain upon crop residue application was positively correlated with an increase in the number of diazotrophic and total bacteria. The data on bacterial numbers suggest that the gain of N in the longterm N balance is most likely due to an N input by biological nitrogen fixation. In addition, evidence exists from related studies that the proliferation of diazotrophs and total bacteria in the rhizosphere due to crop residue application stimulated root growth of pearl millet, and thus improved the phosphorus (P) acquisition in the P deficient soil.     

Carbon dioxide and gaseous nitrogen emissions from biochar‐amended soils under wastewater irrigated urban vegetable production of Burkina Faso and Ghana

To quantify carbon (C) and nitrogen (N) losses in soils of West African urban and peri‐urban agriculture (UPA) we measured fluxes of CO₂‐C, N₂O‐N, and NH₃‐N from irrigated fields in Ouagadougou, Burkina Faso, and Tamale, Ghana, under different fertilization and (waste‐)water regimes. Compared with the unamended control, application of fertilizers increased average cumulative CO₂‐C emissions during eight cropping cycles in Ouagadougou by 103% and during seven cropping cycles in Tamale by 42%. Calculated total emissions measured across all cropping cycles reached 14 t C ha^?1 in Ouagadougou, accounting for 73% of the C applied as organic fertilizer over a period of two years at this site, and 9 t C ha^?1 in Tamale. Compared with unamended control plots, fertilizer application increased N₂O‐N emissions in Ouagadougou during different cropping cycles, ranging from 37 to 360%, while average NH₃‐N losses increased by 670%. Fertilizer application had no significant effects on N₂O‐N losses in Tamale. While wastewater irrigation did not significantly enhance CO₂‐C emissions in Ouagadougou, average CO₂‐C emissions in Tamale were 71% (1.6 t C ha^?1) higher on wastewater plots compared with those of the control (0.9 t C ha^?1). However, no significant effects of wastewater on N₂O‐N and NH₃‐N emissions were observed at either location. Although biochar did not affect N₂O‐N and NH₃‐N losses, the addition of biochar could contribute to reducing CO₂‐C emissions from urban garden soils. When related to crop production, CO₂‐C emissions were higher on control than on fertilized plots, but this was not the case for absolute CO₂‐C emissions.     

Soil Factors Affecting Yield,Quality, and Response to Nitrogen of Sugar Beets Grown on Light-Textured Soils in Northern Greece

For 7 years (1997–2003), five nitrogen (N) rates (0, 60, 120, 180, and 240 kg N ha^?1) were applied to sugar beets arranged in randomized complete block (RCB) design experiments with six replications and grown on light soils (sand content >50 g kg^?1) in northern Greece. The aim of this work was to identify soil characteristics that affect yield, quality, and sugar beet response to N fertilization. Before sowing, soil analyses were conducted in control plots (0 kg N ha^?1) at two depths (0–30 and 30–60 cm). Soils differed in their physical and chemical properties and especially in sand content, which ranged from 500 to 732 g kg^?1. Quantitative (root number, RN; root yield, RY; and sugar yield, SY) and qualitative (percentage sucrose content in fresh root weight, SC; potassium, K; sodium, Na; and α-amino N) traits of control plots were used as soil fertility index. The RN was positively affected by clay content, and RY and SY were positively related with sand and negatively with silt content. The SC was negatively affected by soil (NO₃)-N and sodium (Na) concentrations. Also, soil (NO₃)-N concentration was positively related with root impurities (K, Na, α-amino N). In combined data over years, N rates had a negative effect on the RN. The RY was the only trait affected by years, N rates, and their interaction. The SC and SY differed significantly between years, and N rates affected significantly the former but not the latter. In combined data over years, N rates were curvilinearly related with Na concentration in roots, whereas a strong, linear relationship was found between α-amino N concentration and N rates. To study the significant years × N rates interaction evidenced for the RY, the relative response (RR) of the RY to N was introduced. Actually, the RR expresses the increase or decrease of the RY for a 150 kg N ha^?1 rate compared to the control (0 kg N ha^?1). The RR was strongly related with soil K concentration at the 0- to 30-cm depth (y = –0.00002x² + 0.0082x + 0.5085, r² = 0.92, P < 0.01, n = 7) and with total N concentration at the deeper layer (y = 1.8335x² – 3.5312x + 2.6614, r² = 0.88, P < 0.05, n = 6). Thus, the RY response to a rate of 150 kg N ha^?1, which is the commonly applied to the sugar beet crop in Greece, can be predicted reliably by soil characteristics (K and total N concentration) determined before sowing. The strong relationship between soil K concentration and sugar beet response to N merits further research.     

Fate of fertilizer nitrogen.

Results are presented from a three year lysimeter investigation, employing single (¹⁵NH₄NO₃) and double (¹⁵NH₄¹⁵NO₃) labelled ammonium nitrate to study the uptake of soil and fertilizer nitrogen by cut ryegrass at 250, 500 and 900 kg N ha^?1 a^?1. Average annual recoveries of nitrogen were equivalent to 99,76 and 50% of the nitrogen added at 250, 500 and 900 kg N ha^?1, respectively. At 250 kg N ha^?1 the difference between the overall nitrogen recovery and the fertilizer recovery was almost entirely attributable to pool substitution resulting from mineralization/immobilization turnover (MIT). At 900 kg N ha^?1 both the low overall recovery of nitrogen and the low fertilizer recovery reflected the large excess of available nitrogen over crop requirements. No evidence of ‘priming’ was obtained. Analysis of the results from single and double labelled lysimeters using simultaneous equations indicated that at 250 kg N ha^?1,～70% of the nitrogen in the crop was derived from the ammonium pool. At 500 kg N ha^?1 this dropped to 64%, while at 900 kg N ha^?1 the figure was 59%. There was a suggestion that at the lower application rates, preferential uptake of ammonium was occurring but that as N supply exceeded crop requirements, nitrate was the major N source. Despite the preferential exploitation of the ammonium pool, at 250 and 500 kg N ha^?1 pool substitution resulting from MIT resulted in lower recoveries of fertilizer ammonium compared with fertilizer nitrate.     

Reaktion der Zuckerrübe (Beta vulgaris var. altissima) auf die Kaliumdüngung – ein 20‐jähriger Feldversuch

Response of sugar beet ( Beta vulgaris var. altissima ) to potassium fertilization—a 20‐year field experiment A long‐term fertilizer experiment was performed to develop a K fertilization strategy to achieve highest extractable sugar yields (BZE). Sugar beet was grown in a crop rotation with wheat and barley on an alluvial soil (clayic silt) in Lower Saxony with annual recycling of straw and beet tops, respectively. Since 1983, the treatments were as follows: 1) K fertilization with 0, 29, 58, 87,174, and 524 kg K ha^–1 a^–1 corresponding to 0, 0.5, 1, 1.5, 3, and 9 times the average annual K removal by the marketable products of the crop rotation—since 1995, the two highest treatments (3 and 9 times the removal) received only 174 kg ha^–1 every third year; 2) K fertilization according to the average K removal, given each year (58 kg K ha^–1) or every third year (174 kg ha^–1) to sugar beet; 3) annual K fertilization of 87 kg K ha^–1 (1.5 times the removal) applied in autumn or spring, respectively; 4) annual K fertilization, applied as mineral fertilizer or as organic material (recycling of grain and straw or root and leaves); 5) application of 29 kg NaCl ha^–1 to sugar beet supplemental to a yearly application of 58 kg K ha^–1. Both root yield and soil concentration of lactate‐soluble K increased with K fertilization up to the highest K treatment. The extractable sugar content reached a maximum at a yearly application of 174 kg K ha^–1. Averaged over years, the extractable sugar yield (BZE) increased up to the highest K application. The time of K application (autumn or spring) and the source of K (mineral fertilizer or organic material) had no effect on BZE. An additional fertilization with NaCl increased BZE only slightly in single years. Low‐grade muriate of potash containing 33% K and 3% Na can thus be used. The economically optimal K‐fertilization rate was 174 kg K ha^–1 given once in the crop rotation to sugar beet. A soil K concentration of about 110 mg (kg soil)^–1 (lactate‐extractable K) is sufficient in this soil to achieve a high BZE.     

Improving dryland cropping system nitrogen balance with no‐tillage and nitrogen fertilization

Studies on N balance due to N inputs and outputs and soil N retention to measure cropping system performance and environmental sustainability are limited due to the complexity of measurements of some parameters. We measured N balance based on N inputs and outputs and soil N retention under dryland agroecosystem affected by cropping system and N fertilization from 2006 to 2011 in the northern Great Plains, USA. Cropping systems were conventional tillage barley (Hordeum vulgaris L.)–fallow (CTB‐F), no‐tillage barley–fallow (NTB‐F), no‐tillage barley–pea (Pisum sativum L.) (NTB‐P), and no‐tillage continuous barley (NTCB). In these cropping systems, N was applied to barley at four rates (0, 40, 80, and 120 kg N ha^?1), but not to pea and fallow. Total N input due to N fertilization, pea N fixation, soil N mineralization, atmospheric N deposition, nonsymbiotic N fixation, and crop seed N and total N output due to grain N removal, denitrification, volatilization, N leaching, gaseous N (NO_x) emissions, surface runoff, and plant senescence were 28–37% greater with NTB‐P and NTCB than CTB‐F and NTB‐F. Total N input and output also increased with increased N rate. Nitrogen accumulation rate at the 0–120 cm soil depth ranged from –32 kg N ha^?1 y^?1 for CTB‐F to 40 kg N ha^?1 y^?1 for NTB‐P and from –22 kg N ha^?1 y^?1 for N rates of 0 kg N ha^?1 to 45 kg N ha^?1 y^?1 for 120 kg N ha^?1. Nitrogen balance ranged from 1 kg N ha^?1 y^?1 for NTB‐P to 74 kg N ha^?1 y^?1 for CTB‐F. Because of increased grain N removal but reduced N loss to the environment and N fertilizer requirement as well as efficient N cycling, NTB‐P with 40 kg N ha^?1 may enhance agronomic performance and environmental sustainability while reducing N inputs compared to other management practices.     

Nitrate leaching in an organic dairy/crop rotationas affected by organic manure type, livestock densityand crop

Abstract. In dairy farming systems the risk of nitrate leaching is increased by mixed rotations (pasture/arable) and the use of organic manure. We investigated the effect of four organic farming systems with different livestock densities and different types of organic manure on crop yields, nitrate leaching and N balance in an organic dairy/crop rotation (barley–grass-clover–grass-clover–barley/pea–winter wheat–fodder beet) from 1994 to 1998. Nitrate concentrations in soil water extracted by ceramic suction cups ranged from below 1 mg NO₃-N l^?1 in 1^st year grass-clover to 20–50 mg NO₃-N l^?1 in the winter following barley/pea and winter wheat. Peaks of high nitrate concentrations were observed in 2^nd year grass-clover, probably due to urination by grazing cattle. Nitrate leaching was affected by climatic conditions (drainage volume), livestock density and time since ploughing in of grass-clover. No difference in nitrate leaching was observed between the use of slurry alone and farmyard manure from deep litter housing in combination with slurry. Increasing the total-N input to the rotation by 40 kg N ha^?1 year^?1 (from 0.9 to 1.4 livestock units ha^?1) only increased leaching by 6 kg NO₃-N ha^?1. Nitrate leaching was highest in the second winter (after winter wheat) following ploughing in of the grass-clover (61 kg NO₃-N ha^?1). Leaching losses were lowest in 1^st year grass-clover (20 kg NO₃-N ha^?1). Averaged over the four years, nitrate concentration in drainage water was 57 mg l^?1. Minimizing leaching losses requires improved utilization of organic N accumulated in grazed grass-clover pastures. The N balance for the crop rotation as a whole indicated that accumulation of N in soil organic matter in the fields of these systems was small.     

Life cycle inventory-based analysis of greenhouse gas emissions from arable land farming systems in Hokkaido,northern Japan

Abstract

To assess their impacts on net global warming, total greenhouse gas emissions (mainly CO₂, N₂O and CH₄) from agricultural production in arable land cropping systems in the Tokachi region of Hokkaido, Japan, were estimated using life cycle inventory (LCI) analysis. The LCI data included CO₂ emissions from on-farm and off-farm fossil fuel consumption, soil CO₂ emissions induced by the decomposition of soil organic matter, direct and indirect N₂O emissions from arable lands and CH₄ uptake by soils, which were then aggregated in CO₂-equivalents. Under plow-based conventional tillage (CT) cropping systems for winter wheat, sugar beet, adzuki bean, potato and cabbage, on-farm CO₂ emissions from fuel-consuming operations such as tractor-based field operations, truck transportation and mechanical grain drying ranged from 0.424 Mg CO₂ ha^?1 year^?1 for adzuki bean to 0.826 Mg CO₂ ha^?1 year^?1 for winter wheat. Off-farm CO₂ emissions resulting from the use of agricultural materials such as chemical fertilizers, biocides (pesticides and herbicides) and agricultural machines were estimated by input–output tables to range from 0.800 Mg CO₂ ha^?1 year^?1 for winter wheat to 1.724 Mg CO₂ ha^?1 year^?1 for sugar beet. Direct N₂O emissions previously measured in an Andosol field of this region showed a positive correlation with N fertilizer application rates. These emissions, expressed in CO₂-equivalents, ranged from 0.041 Mg CO₂ ha^?1 year^?1 for potato to 0.382 Mg CO₂ ha^?1 year^?1 for cabbage. Indirect N₂O emissions resulting from N leaching and surface runoff were estimated to range from 0.069 Mg CO₂ ha^?1 year^?1 for adzuki bean to 0.381 Mg CO₂ ha^?1 year^?1 for cabbage. The rates of CH₄ removal from the atmosphere by soil uptake were equivalent to only 0.020–0.042 Mg CO₂ ha^?1 year^?1. From the difference in the total soil C pools (0–20 cm depth) between 1981 and 2001, annual CO₂ emissions from the CT and reduced tillage (RT) soils were estimated to be 4.91 and 3.81 Mg CO₂ ha^?1 year^?1, respectively. In total, CO₂-equivalent greenhouse gas emissions under CT cropping systems in the Tokachi region of Hokkaido amounted to 6.97, 7.62, 6.44, 6.64 and 7.49 Mg CO₂ ha^?1 year^?1 for winter wheat, sugar beet, adzuki bean, potato and cabbage production, respectively. Overall, soil-derived CO₂ emissions accounted for a large proportion (64–76%) of the total greenhouse gas emissions. This illustrates that soil management practices that enhance C sequestration in soil may be an effective means to mitigate large greenhouse gas emissions from arable land cropping systems such as those in the Tokachi region of northern Japan. Under RT cropping systems, plowing after harvesting was omitted, and total greenhouse gas emissions from winter wheat, sugar beet and adzuki bean could be reduced by 18%, 4% and 18%, respectively, mainly as a result of a lower soil organic matter decomposition rate in the RT soil and a saving on the fuels used for plowing.     

Nitrous oxide emissions after incorporation of winter oilseed rape (Brassica napus L.) residues under two different tillage treatments

The aim of this study was to investigate the effect of crop residues from winter oilseed rape on N₂O emissions from a loamy soil and to determine the effect of different tillage practices on N₂O fluxes. We therefore conducted a field experiment in which crop residues of winter oilseed rape (Brassica napus L., OSR) were replaced with ¹⁵N labelled OSR residues. Nitrous oxide (N₂O) emissions and ¹⁵N abundance in the N₂O were determined for a period of 11 months after harvest of OSR and in the succeeding crop winter wheat (Triticum aestivum L.) cultivated on a Haplic Luvisol in South Germany. Measurements were carried out with the closed chamber method in a treatment with conventional tillage (CT) and in a treatment with reduced soil tillage (RT). In both tillage treatments we also determined N₂O fluxes in control plots where we completely removed the crop residues. High N₂O fluxes occurred in a short period just after OSR residue replacement in fall and after N‐fertilization to winter wheat in the following spring. Although N₂O emissions differed for distinct treatments and sub‐periods, cumulative N₂O emissions over the whole investigation period (299 days) ranged between 1.7 kg and 2.4 kg N₂O‐N ha^?1 with no significant treatment effects. More than half of the cumulative emissions occurred during the first eight weeks after OSR replacement, highlighting the importance of this post‐harvest period for annual N₂O budgets of OSR. The contribution of residue N to the N₂O emission was low and explained by the high C/N‐ratio fostering immobilization of mineral N. In total only 0.03% of the N₂O‐N emitted in the conventional tillage treatment and 0.06% in the reduced tillage treatment stemmed directly from the crop residues. The ¹⁵N recovery in the treatments with crop residues was 62.8% (CT) and 75.1% (RT) with more than 97% of the recovered ¹⁵N in the top soil. Despite our measurements did not cover an entire year, the low contribution of the OSR residues to the direct N₂O emissions shows, that the current IPCC tier 1 approach, which assumes an EF of 1%, strongly overestimated direct emissions from OSR crop residues. Furthermore, we could not observe any relationship between tillage and crop residues on N₂O emission, only during the winter period were N₂O emissions from reduced tillage significantly higher compared to conventional tillage. Annual N₂O emission from RT and CT did not differ.     

Co-incorporation of biodegradable wastes with crop residues to reduce nitrate pollution of groundwater and decrease waste disposal to landfill

Return of high nitrogen (N) content crop residues to soil, particularly in autumn, can result in environmental pollution resulting from gaseous and leaching losses of N. The EU Landfill Directive will require significant reductions in the amounts of biodegradable materials going to landfill. A field experiment was set up to examine the potential of using biodegradable waste materials to manipulate losses of N from high N crop residues in the soil. Leafy residues of sugar beet were co‐incorporated into soil with materials of varying C:N ratios, including molasses, compactor waste, paper waste, green waste compost and cereal straw. The amendment materials were each incorporated to provide approximately 3.7 t C per hectare. The most effective material for reducing nitrous oxide (N₂O) production and leaching loss of NO₃^? was compactor waste, which is the final product from the recycling of cardboard. Adding molasses increased N₂O and NO₃^? leaching losses. Six months following incorporation of residues, the double rate application of compactor waste decreased soil mineral N by 36 kg N per hectare, and the molasses increased soil mineral N by 47 kg N per hectare. Compactor waste reduced spring barley grain yield by 73% in the first of years following incorporation, with smaller losses at the second harvest. At the first harvest, molasses and paper waste increased yields of spring barley by 20 and 10% compared with sugar beet residues alone, and the enhanced yield persisted to the second harvest. The amounts of soil mineral N in the spring and subsequent yields of a first cereal crop were significantly correlated to the lignin and cellulose contents of the amendment materials. Yield was reduced by 0.3–0.4 t/ha for every 100 mg/g increase in cellulose or lignin content. In a second year, cereal yield was still reduced and related to the cellulose content of the amendment materials but with one quarter of the effect. Additional fertilizer applied to this second crop did not relieve this effect. Although amendment materials were promising as tools to reduce N losses, further work is needed to reduce the negative effects on subsequent crops which was not removed by applying 60 kg/ha of fertilizer N.     

Nitrous oxide, methane and ammonia emissions following slurry spreading on grassland

In Sweden, 90% of ammonia (NH₃) emissions to the atmosphere originate from agriculture, predominantly from animal manure handling. It is well known that incorporation of manure into soil can reduce NH₃ emissions after spreading. However, there is a risk of increased nitrous oxide (N₂O) and methane (CH₄) emissions caused by bacterial activity and limited oxygen availability under these conditions. A full‐scale injector was developed and evaluated in a field experiment on grassland. Cattle slurry was either injected in closed slots 5 cm below ground or band spread on the soil surface above the crop canopy at a rate of 25 t ha^?1. In a control treatment, no slurry was applied. During a 5‐day period after application, NH₃ emissions were measured using an equilibrium concentration method. Gas samples for estimating CH₄ and N₂O emissions were also collected during 7 weeks following slurry application. Injection in closed slots resulted in no detectable NH₃ emissions. After band spreading, however, NH₃ emissions corresponded to nearly 40% of the total ammoniacal nitrogen in the applied slurry. The injection of slurry gave rise to a broad peak of N₂O emissions during the first 3 weeks after application. In total, for the measuring period, N₂O emissions corresponded to 0.75 kg N ha^?1. Band spreading resulted in only a very small N₂O release of about 0.2 kg N ha^?1 during the same period. Except for the first sampling occasion, the soil was predominantly a sink for CH₄ in all the treatments. The use of the injector without slurry application reduced grass yield during unfavourable growing conditions. In conclusion, shallow injection in closed slots seems to be a promising technique to reduce negative environmental impacts from NH₃ emissions with a limited release of N₂O and CH₄.     

Effect of cattle slurry application techniques on N2O and NH3 emissions from a loamy soil

We determined N₂O fluxes from an unfertilized control (CON), from a treatment with mineral N‐fertilizer (MIN), from cattle slurry with banded surface application and subsequent incorporation (INC), and from slurry injection (INJ) to silage maize (Zea mays, L.) on a Haplic Luvisol in southwest Germany. In both years, amount of available N (total N fertilized + N_min content before N application) was 210 kg N ha^?1. In the slurry treatment of the 1^st year, 140 kg N ha^?1 were either injected or incorporated, whereas 30 kg N ha^?1 were surface applied to avoid destruction of the maize plants. In the 2^nd year, all fertilizers were applied with one single application. We calculated greenhouse gas emissions (GHG) on field level including direct N₂O emissions (calculated from the measured flux rates), indirect N₂O emissions (NH₃ and ${\mathrm{NO}}_3^{-}$ induced N₂O emission), net CH₄ fluxes, fuel consumption and pre‐chain emissions from mineral fertilizer. NH₃ losses were measured in the 2^nd year using the Dräger‐Tube Method and estimated for both years. NH₃ emission was highest in the treatment without incorporation. It generally contributed less than 5% of the greenhouse gas (GHG) emission from silage maize cultivation. The mean area‐related N₂O emission, determined with the closed chamber method was 2.8, 4.7, 4.4 and 13.8 kg N₂O‐N ha^?1 y^?1 for CON, MIN, INC, and INJ, respectively. Yield‐related N₂O emission showed the same trend. Across all treatments, direct N₂O emission was the major contributor to GHG with an average of 79%. Trail hose application with immediate incorporation was found to be the optimum management practice for livestock farmers in our study region.     

Nitrous oxide emissions from arable soils in Germany — An evaluation of six long‐term field experiments

In this study emissions of N₂O from arable soils are summarized using data from long‐term N₂O monitoring experiments. The field experiments were conducted at six sites in Germany between 1992 and 1997. The annual N‐application rate ranged from 0 to 350 kg N ha^—1. Mineral and organic N‐fertilizer applications were temporarily split adapted to the growth stage of each crop. N‐fertilizer input and N‐yield by the crops were used to calculate the In/Out‐balance. The closed chamber technique was applied to monitor the N₂O fluxes from soil into the atmosphere. If possible, plants were included in the covers. Annual N₂O emission values were based on flux rate measurements of an entire year. The annual N₂O losses ranged from 0.53 to 16.78 kg N₂O‐N ha^—1 with higher N₂O emissions from organically fertilized plots as compared to minerally fertilized plots. Approximately 50% of the total annual emissions occurred during winter. No significant relationship between annual N₂O emissions and the respective N‐fertilization rate was found. This was attributed to site‐ and crop‐specific effects on N₂O emission. The calculation of the N₂O emission per unit N‐yield from winter cereal plots indicates that the site effect on N₂O emission is more important than the effect of N‐fertilization. From unfertilized soils at the sites Braunschweig and Timmerlah a N‐yield of 60.0 kg N ha^—1 a^—1 and N₂O emissions of 2 kg N ha^—1 a^—1 were measured. This high background emission was assigned to the amount and turnover of soil organic matter. For a crop rotation at the sites Braunschweig and Timmerlah the N In/Out‐balance over a period of four years was identified as a suitable predictor of N₂O emissions. This parameter characterizes the efficiency of N‐fertilization for crop production and allows for N‐mineralization from the soil.     

Nitrous oxide emissions under a four-year crop rotation system in northern Japan: impacts of reduced tillage,composted cattle manure application and increased plant residue input

In the context of their role in global warming, nitrous oxide (N₂O) emissions from agricultural soil under different management practices were studied in Hokkaido, northern Japan. To assess the impacts of reduced tillage, composted cattle manure-based fertilization and amendments with crop residues and green manure on N₂O emissions from soil, a field experiment was conducted under a four-year crop rotation on a well-drained Andisol. The crop rotation included potato (Solanum tuberosum L.) or sweet corn (Zea mays L.), winter wheat (Triticum aestivum L.), sugar beet (Beta vulgaris L. subsp. vulgaris) and soybean (Glycine max (L.) Merr.). The cumulative N₂O emissions for the four-year study period differed widely (0.33 to 4.90?kg?N?ha^?1), depending on the treatments imposed, being the greatest for a combination of conventional moldboard plow tillage, composted cattle manure-based fertilization and increased plant residue input, and the lowest for a combination of conventional tillage, chemical fertilizer-based fertilization and normal plant residue input treatments. The cumulative N₂O emissions under reduced tillage were all small, irrespective of fertilization and plant residue input treatments. Composted cattle manure-based fertilization (P?≤?0.01) and increased plant residue input (P?≤?0.01) significantly increased cumulative N₂O emissions. Tillage showed a significant interaction with fertilization and plant residue input, indicating that N₂O emissions were enhanced when composted cattle manure, crop residues and green manure were incorporated by conventional tillage. In the present study, the N₂O emission factors for chemical fertilizer, composted cattle manure and crop residues were 0.26?±?0.44, 0.11?±?0.16 and ?0.03?±?0.52%, respectively, all much lower than the country-specific emission factor for Japan's well-drained soils (0.62%) and the default emission factor used in the IPCC guideline (1%).     

Lysimeterstudie zum Einfluss von Düngung und Bewirtschaftung auf die Ertragsbildung,den Wasserhaushalt und die Nährstoffauswaschung im Trockengebiet der Uckermark

Lysimeter study about the effect of fertilization and management on yield, water balance, and solute leaching in the dry region of the Uckermark Results are presented of a lysimeter study on the effects of fertilization and management on yield, seepage rate, and solute leaching in the dry region of the Uckermark (Northeast Germany) from 1992 to 1999. The crop rotation included sugar beet, summer barley, pea, and winter wheat with fertilization of 280 and 400 kg N ha^—1 within the crop rotation. Additionally to the mineral fertilization, sugar beet was fertilized with the sugar beet leaf or slurry. The average annual seepage rate was 13.7 mm, the nitrogen leaching was 4.3 kg N ha^—1, and the phosphorus leaching was 0.008 kg P ha^—1. Differences between the treatments were negligible and insignificant. The amount of the precipitation from April to September had a significant influence on yields. Furthermore, results of water use efficiency and the effect of different nitrogen rates on yields are presented.     

Efficiency of Potassium Fertilization and Salicylic Acid on Yield and Nutrient Accumulation of Sugar Beet Grown on Saline Soil

Rising soil salinity has been a major problem in the soils of Egypt in recent decades. Potassium fertilization and salicylic acid (SA) play an important role in promoting plants to tolerate salt stress and increased the yield of sugar beet crop. A field experiment on sugar beet (Beta vulgaris L.) grown on saline soil was carried out during 2014 growing season in Port Said Governorate, Egypt, to study the effect of potassium fertilization of the soil at applications of 0, 100, 150, and 200 kg potassium (K) ha^?1 and foliar spray of SA by solution of 1000 mg L^?1, twice (1200 L ha^?1 each time) on yield and nutrient uptake. Application of 200 kg K ha^?1 in combination with salicylic foliar spray gave the highest root length, root diameter, shoot and root yield, sucrose, juice purity percentage, gross sugar yield, and white possible extractable sugar, nitrogen (N), phosphorus (P), and potassium (K) content, and uptake of sugar beet. The highest increase in sucrose (20%) as well as white possible extractable sugar (184%) was obtained by 200 kg K ha^?1 in combination with salicylic foliar spray compared with untreated soil with potassium fertilization and without salicylic foliar spray.     

Eucalyptus biochar application enhances Ca uptake of upland rice,soil available P,exchangeable K,yield, and N use efficiency of sugarcane in a crop rotation system

It was hypothesized that the application of eucalyptus biochar enhances nutrient use efficiencies of simultaneously supplied fertilizer, as well as provides additional nutrients (i.e., Ca, P, and K), to support crop performance and residual effects on subsequent crops in a degraded sandy soil. To test this hypothesis, we conducted an on‐farm field experiment in the Khon Kaen province of Northeastern Thailand to assess the effects of different application rates of eucalyptus biochar in combination with mineral fertilizers to upland rice and a succeeding crop of sugarcane on a sandy soil. The field experiment consisted of three treatments: (1) no biochar; (2) 3.1 Mg ha^?1 biochar (10.4 kg N ha^?1, 3.1 kg P ha^?1, 11.0 kg K ha^?1, and 17.7 kg Ca ha^?1); (3) 6.2 Mg ha^?1 biochar (20.8 kg N ha^?1, 6.2 kg P ha^?1, 22.0 kg K ha^?1, and 35.4 kg Ca ha^?1). All treatments received the same recommended fertilizer rate (32 kg N ha^?1, 14 kg P ha^?1, and 16 kg K ha^?1 for upland rice; 119 kg N ha^?1, 21 kg P ha^?1, and 39 kg K ha^?1 for sugarcane). At crop harvests, yield and nutrient contents and nitrogen (N) use efficiency were determined, and soil chemical properties and pH₀ monitored. The eucalyptus biochar material increased soil Ca availability (117 ± 28 and 116 ± 7 mg kg^?1 with 3.1 and 6.2 Mg ha^?1 biochar application, respectively) compared to 71 ± 13 mg kg^?1 without biochar application, thus promoting Ca uptake and total plant biomass in upland rice. Moreover, the higher rate of eucalyptus biochar improved CEC, organic matter, available P, and exchangeable K at succeeding sugarcane harvest. Additionally, 6.2 Mg ha^?1 biochar significantly increased sugarcane yield (41%) and N uptake (70%), thus enhancing N use efficiency (118%) by higher P (96%) and K (128%) uptake, although the sugar content was not increased. Hence, the application rate of 6.2 Mg ha^?1 eucalyptus biochar could become a potential practice to enhance not only the nutrient status of crops and soils, but also crop productivity within an upland rice–sugarcane rotation system established on tropical low fertility sandy soils.     

The crop as indicator for sidedress nitrogen demand in sugar beet production — limitations and perspectives

In 2‐years field experiments near Nienstädt (60 km west of Hannover, northern Germany), the effects of rate and timing of nitrogen (N) application on leaf N‐concentration, leaf greenness (SPAD chlorophyll meter readings), canopy greenness (canopy light reflectance), leaf area development, photosynthetic activity of leaves, and yield and quality of sugar beet were studied. In 1999 (pre‐planting soil mineral N: 15 kg ha^—1), N fertilizer was applied at rates of 0, 105, 125, 145, 165 and 205 kg N ha^—1. In 2000 (pre‐planting soil mineral N: 60 kg ha^—1), an N rate of 100 kg ha^—1 was applied at planting (100/0/0/0) or split applied at planting and 8 (60/40/0/0), 12 (60/0/40/0), and 16 (60/0/0/40) weeks after planting (WAP), respectively. In both years, canopy greenness as indicated by ”︁sensor values” (a combination of the reflectance of visible and near infrared light) changed with crop age. However, at each time of measurement, sensor values precisely reflected the different N application treatments and were significantly correlated with leaf N‐concentrations and SPAD chlorophyll meter readings. Beet yield and processed white sugar yield increased up to an N supply (fertilizer N + pre‐planting soil mineral N) of 160 kg ha^—1. Split N application slightly retarded leaf growth but had no effect on photosynthetic activity per unit leaf area. Beet yield and beet quality were not systematically affected by the timing of N application. Certain application schemes tended to favor either beet yield or beet quality, resulting in similar processed white sugar yields. Our data suggest that moderate N topdressing can be integrated in site‐specific N management systems in sugar beet production. Canopy light reflectance might serve as a useful diagnostic tool to assess the N status and sidedress N demand of sugar beets. However, due to changing sensor values over time, on‐site calibration (using established standard methods or reference plots receiving extra N at planting) will be necessary. The applicability of this approach has to be tested in further field studies.<?show $6#>     

Soil and nutrient losses due to root crops harvesting: a case study from southwestern Iran

Although root crops are widely cultivated in Iran, little is known about soil loss due to crop harvesting (SLCH). We assessed the annual exported soil, soil organic matter (SOM) and nutrients from 47 farms under root crops in southwestern Iran. Soil losses for garlic, potato, sugar beet, radish and beetroot were estimated as 6.27, 2.52, 2.26, 4.10 and 6.95, Mg ha^?1, respectively, which on average was of the order of soil losses by water erosion in the watershed basins of Iran. Total N, P₂O₅ and K₂O losses were estimated as 36.61, 1.10 and 31.50 kg ha^?1 and their costs as 18.24, 0.74 and 19.93 USAlthough root crops are widely cultivated in Iran, little is known about soil loss due to crop harvesting (SLCH). We assessed the annual exported soil, soil organic matter (SOM) and nutrients from 47 farms under root crops in southwestern Iran. Soil losses for garlic, potato, sugar beet, radish and beetroot were estimated as 6.27, 2.52, 2.26, 4.10 and 6.95, Mg ha^?1, respectively, which on average was of the order of soil losses by water erosion in the watershed basins of Iran. Total N, P₂O₅ and K₂O losses were estimated as 36.61, 1.10 and 31.50 kg ha^?1 and their costs as 18.24, 0.74 and 19.93 US$ ha^?1, respectively. For the whole country, total soil, N, P₂O₅, K₂O and SOM losses for garlic, potato and sugar beet were estimated as 731.7 × 10³, 836, 27, 476 and 14.5 × 10³ Mg, respectively (radish and beetroot were excluded due to no reliable data on their planted areas). Correlation analysis showed no significant relationship between soil properties and SLCH (except soil moisture content for radish and clay content for beetroot). The findings indicated that the exported soil, SOM and nutrients were at such levels that SLCH should be considered in soil erosion studies.     

Nutrient content of precipitation over Iowa

Nutrient content and pH of precipitation samples collected at six sites during 1971–1973 were studied to determine the fraction of rainfall and snowmelt and the amounts of N, S, and P added by precipitation over Iowa The amount of NH₄-N ha^?1 added by precipitation annually at each site was about equal to that added as N0₃-N. The amounts of inorganic N ha^?1 yr^?1 added ranged from 10 kg in north-central to 14 kg in west-central Iowa, and the annual amounts of S0₄-S ha^?1 added ranged from 13 kg in northeastern to 17 kg in north-central Iowa. It is estimated that, on average, precipitation adds about 0.6 kg of NH₄-N, 0.6 kg of N0₃-N, and 1.5 kg of S0₄ -S ha^?1 monthly in Iowa. However, the data indicated that, on an annual basis, the contribution of precipitation to P in soil is very small; at the most, about 0.1 kg of water-soluble P0₄-P ha^?1 was added annually in Iowa. No N0₂-N could be detected in any of the precipitation samples analyzed. Average pH value of the rainfall and snowmelt samples collected at each site during each year was about 6, individual samples seldom reached as low as pH 4. The data indicate that the concentration of S0₄-S in precipitation in this region is seasonal, high during fall and winter and low during spring and summer.