15N-labelled Ammonium Sulphate Research Articles

Higher lime rates for greater nitrogen recovery: A long-term no-till experiment labeled with 15N

Soil acidity limits crop growth and yield all over the world. Low grain yields is usually associated with poor soil fertility; however, little attention has been given to the nitrogen-based fertilizer use efficiency in soils managed with lime. Given the current scenario of uncertainties regarding the availability and prices of fertilizers, our study aimed to understand how maize intercropped with ruzigrass and soybean plants develop in long-term soils managed with lime rates, and what the fate of the 15N–labeled ammonium sulfate [(15NH4)2SO4] applied in the soil-plant system. The treatments consisted of four dolomitic lime rates applied to the soil surface [control, half the recommended lime rate (½ RLR), full recommended lime rate (1 RLR) and double the recommended lime rate (2 RLR)]. The higher lime rate (2 RLR) improved fertility, carbon and nitrogen stocks in the soil profile, and grain and/or stover production of maize, ruzigrass and soybean. As a consequence, maize and ruzigrass recovered a high amount of 15N-fertilizer. On the other hand, soybean recovered less 15N-fertilizer, regardless of treatment, but a greater amount was found in acidic soils. At the end of the maize and soybean growth cycles, our results showed that in 2 RLR-amended soil, the 15N unrecovered was 71% lower than control. Finally, our results suggested that the use of low lime rates (½ RLR) may increase the 15N losses potential to deep layers, whereas low amounts of 15N were found in the subsoil when higher lime rates were applied. Soil acidity management through higher lime rates leads, over time, to increased soil fertility, resulting in a favorable environment for plant growth and the use of nitrogen fertilizers. In this way, it is possible to obtain a more productive and less costly agricultural system, and with less potential to pollute the environment.

Long term co-application of lime and phosphogypsum increases 15 N recovery and reduces 15 N losses by modulating soil nutrient availability, crop growth and N cycle genes

In no-tillage rotation systems, the recovery of nitrogen (N) fertilizer in the soil–plant system is affected by soil fertility and biological changes caused by the surface application of lime (L) and phosphogypsum (PG). Here we assessed the effect of surface-applied L and/or PG on the fate of 15N-labeled fertilizer, soil chemical properties, microbial gene copy number (16 S rRNA of prokaryotes and genes of N cycle) and grain yield of maize (Zea mays L. intercropped with ruzigrass) in rotation with soybean [Glycine max (L.) Merrill] during two growing seasons. We found that applying L improved soil fertility, particularly when combined with PG (LPG treatment), resulting in higher grain yield. Moreover, compared with the control, the recovery of 15N-labeled ammonium sulfate [(15NH4)2SO4] increased in maize and ruzigrass dry matter but decreased in soybean grown on the residue of the first growing season in two treatments (L and LPG). The losses of 15N-labeled fertilizer were highest in the control and PG treatments. A large amount of 15N-labeled fertilizer was found in the deep layers of PG-amended soil, indicating leaching of fertilizer-derived 15N. Conversely, the analysis of soil microbial N cycle genes revealed that the abundances of denitrifiers were highest in the control (no correctives applied), suggesting that the N fertilizer remaining in the soil increased denitrification rates. Surface application of a combination of L and PG is clearly a feasible strategy for increasing soil fertility, 15N recovery from fertilizer, and grain yield while reducing environmental pollution associated with nitrification and denitrification.

A method of assessing essential amino acid availability from microbial and ruminally undegraded protein in lactating dairy cows

The objective of this study was to extend a stable isotope-based assessment of AA absorption from rumen-degradable protein (RDP) sources to include determination of essential AA (EAA) availability from microbial protein (MCP). To demonstrate the technique, a study using a 2 × 2 factorial arrangement of treatments applied in a repeated 4 × 4 Latin square design was undertaken. Factors were high and low rumen-degradable protein and high and low starch. Twelve lactating cows were blocked into 3 groups according to days in milk and randomly assigned to the 4 treatment sequences. Each period was 14 d in length with 10 d of adaption followed by 4 d of ruminal infusions of 15N-labeled ammonium sulfate. On the last day of each period, a 13C-labeled AA mixture was infused into the jugular vein over a 6-h period to assess total AA entry. Rumen, blood, urine, and milk samples were collected during the infusions. Ruminal bacteria and blood samples were assessed for AA enrichment. Total plasma AA absorption rates were derived for 6 EAA from plasma 13C AA enrichment. Absorption of 6 EAA from MCP was calculated from total AA absorption based on 15N enrichment in blood and rumen bacteria. Essential AA absorption rates from total protein, MCP, and rumen-undegradable protein were derived with standard errors of the mean of 6, 14, and 14%, respectively. An average of 45% of absorbed EAA were from MCP, which varied among 6 EAA and was interactively affected by starch and RDP in diets. Microbial AA availability measured by isotope dilution method increased with the high RDP diets and was unaffected by starch level, except for Met, which decreased with high starch. Microbial protein outflow, estimated from urinary purine derivatives, increased with RDP and was not significantly affected by starch. This was consistent with measurements from the isotope dilution method. Total AA absorption rates measured from isotope dilution were similar to estimates from CNCPS (v. 6.55), but a lower proportion of absorbed AA was derived from MCP for the former method. Compared with the isotope and CNCPS estimates, the Fleming model underestimated microbial EAA and total EAA availability. An average of 58% of the absorbed EAA was converted into milk, which varied among individual AA and was interactively affected by starch and RDP in diets. The isotope dilution approach is advantageous because it provides estimates of EAA availability for individual EAA from rumen-undegradable protein and MCP directly with fewer errors of measurement than can be achieved with intestinal disappearance methods.

Available Nitrogen in Paddy Soils Depth: Influence on Rice Root Morphology and Plant Nutrition

Nitrogen (N) is a key nutrient for rice (Oryza sativa L.) and its availability in soil profile can influence the plant root morphology and total nutrient uptake. This study evaluated if N from deeper soil layers would increase rice root growth, N uptake and influence plant nutritional status. Flooded rice was grown in undisturbed soil samples from three locations with 15N-labeled ammonium sulfate application at different depths (0, 10, 20, 30, and 45 cm). At rice heading, chlorophyll content and photosynthesis rate were measured at flag leaves and rice biomass production, root morphology, and total N and 15N uptake were evaluated. Higher biomass and N uptake were observed with N application at near soil surface layers. The majority of rice N uptake was derived from soil, which was more evident when N fertilizer was injected at 45 cm deep (on average 74%). The highest root growth was observed at the near surface layers with constant decrease in depth, up to 60 cm. Roots from deeper layers exhibited smaller diameter, as they were mainly highly branched roots. The N application at 30 and 45 cm depths provided N later in the season, resulting in plants with lower total biomass but with higher N content in aboveground biomass, with higher chlorophyll content, photosynthesis rate, and carboxylation efficiency by Rubisco. The N available below 20 cm contributes to plant nutrition and root growth, hence soils with available N in depth likely cause plants to function more optimally in photosynthates supply.

Translocation and recovery of 15N-labeled N derived from the foliar uptake of 15NH3 by the greenhouse tomato (Lycopersicon esculentum Mill.)

In order to completely evaluate ammonia emission from greenhouse vegetable fields, crop canopy absorption should not be neglected. The foliar uptake of NH3 applied at two growth stages and the subsequent 15N-labeled N translocation to other plant components were investigated under greenhouse conditions using chambers covered with the soil of a tomato field. Treatments comprised three NH3-N application rates (70, 140, and 210 mg/plot) using 15N-labeled ammonium sulfate. Plants were harvested immediately after exposure for 24 h, and the total N concentrations and 15N/14N ratios were determined. With increased NH3 concentration, total 15NH3-N absorption increased considerably, whereas the applied 15NH3-N uptake decreased gradually. The tomato plants absorbed 33–38% and 24–31% of the 15NH3-N generated at the anthesis and fruit growth stages, respectively. A total of 71–80% of the recovered NH3 was observed in the leaves and 20–30% of the recovered NH3 was remobilized to other components. Among them, an average of 10% of the absorbed 15NH3-N was transferred into the tomato fruits. All these results indicated the potential of the tested tomatoes for the foliar uptake of atmospheric 15NH3 and the distribution of 15N-labeled vegetative N among different plant components. The results are of great importance for the complete evaluation of nitrogen use efficiency in the greenhouse tomato fields.

Rice nitrogen uptake as affected by different nitrogen application depths

ABSTRACT Subsoil nitrogen (N) can contribute to rice (Oryza sativa L.) nutrition and affect its response to N fertilization. The N recovery by depth for flooded rice using 15N was evaluated in three undisturbed soils (varying in their physical and chemical properties) in a greenhouse experiment. Rice was grown after 15N-labeled ammonium sulfate application at the soil surface and at 0.10, 0.20, 0.30, and 0.45 m depths. The N located at greater depths was absorbed over time, resulting in a similar 15N concentration in leaves among treatments at rice heading. The N-fertilizer application at the near soil surface resulted in higher dry matter production for all soils, with a constant decrease with depth. Although, 15N recovery and N derived from fertilizer were greater with N application at 0.10, 0.20, or 0.30 m depth, probably due to N dilution effect caused by soil N and greater N loss at the soil surface. The intensity of 15N recovery from 0.45 m was related to soil properties, such as hydraulic conductivity. Even later in the season, rice plants effectively used N from subsoil layers, therefore greater soil depths should be considered in studies regarding correlation and calibration of soil-based N tests for N-fertilizer recommendations.

Contrasting impacts of two weed species on lowbush blueberry fertilizer nitrogen uptake in a commercial field.

Numerous studies have speculated that lowbush blueberry (Vaccinium angustifolium) is less efficient than weed species at taking up inorganic nitrogen (N) derived from fertilizers, thus raising questions as to the effectiveness of N fertilization in commercial fields. However, competition for acquiring N as well as specific interactions between blueberry and companion weeds characterized by contrasted functional traits remain poorly documented. Here, we assessed fertilizer-derived N acquisition efficiency and biomass production in lowbush blueberry and two common weed species that have different functional traits—sweet fern (Comptonia peregrina), a N2-fixing shrub, and poverty oat grass (Danthonia spicata), a perennial grass—in a commercial blueberry field in Québec, Canada. In 2015, 15N-labelled ammonium sulfate was applied at a rate of 45 kg ha-1 to 1 m2 field plots containing lowbush blueberry and one of the two weeds present at several different density levels (0 to 25 plants m-2). In 2016, each plot was harvested to determine vegetative biomass and the percentage of fertilizer-derived N recovered (PFNR) in each species. The PFNR was higher in blueberry (24.4 ± 9.3%) than in sweet fern (13.4 ± 2.6%) and poverty oat grass (3.3 ± 2.9%). However, lowbush blueberry required about four times more root biomass than sweet fern and poverty oat grass to uptake an equivalent amount of N from ammonium sulfate. The PFNR in poverty oat grass increased with plant density (from 0.8% to 6.4% at 2–3 and >6 plants m-2, respectively), which resulted in a decrease in blueberry’s PFNR (from 26.0 ± 1.4% to 8.6 ± 1.8%) and aboveground vegetative biomass production (from 152 ± 58 to 80 ± 28 g m-2). The increase in biomass production and N content in sweet fern with increasing plant density was not accompanied by an increase in PFNR (29.7 ± 8.4%), suggesting an increasing contribution of atmospherically-derived N. This mechanism (i.e., N sparing) likely explained blueberry’s higher biomass production and N concentration in association with sweet fern than with poverty oat grass. Overall, our study confirms lowbush blueberry low efficiency (on a mass basis) at taking up N derived from the fertilizer as compared to weeds and reveals contrasted and complex interactions between blueberry and both weed species. Our results also suggest that the use of herbicides may not be necessary when poverty oat grass is present at a low density (<15 plants of poverty oat grass m-2) and that adding inorganic N fertilizer is counterproductive when this species is present at a high density as it takes up as much fertilizer as lowbush blueberry.

Ball milling pretreatment affects the content of fixed ammonium in soils in response to the content of exchangeable ammonium

ABSTRACTAnalysis of fixed ammonium (NH4+) in soils by the most common method requires the subsample to be ground to pass through a 100-mesh sieve. We tested a hypothesis that the ball milling pretreatment for the analysis of fixed NH4+ may influence the analytical results depending on the content of exchangeable NH4+. Five paddy soils collected from the surface layer in Japan were treated with 15N-labeled ammonium sulfate at 0, 100, 500, or 1000 mg N kg−1, incubated aerobically at 30°C for 7 days, and air-dried. Part of each soil was then ground in a vibration ball mill at 1200 rpm for 10 min as a pretreatment (BMP treatment). The samples with and without the BMP treatment were analyzed for exchangeable NH4+ and total fixed NH4+. The samples that received 0 or 1000 mg N kg−1 were also analyzed for nonexchangeable 15N (total fixed 15NH4+ plus organic 15N) and hot KCl-extractable organic N. At 0 mg N kg−1, the BMP treatment significantly decreased total fixed NH4+ in all soils and significantly increased exchangeable NH4+ in two of the five soils. The fixation of exchangeable NH4+ started to occur when its content is greater than around 300 mg N kg−1, and its ratio to total fixed NH4+ is greater than around 1.0. At 1000 mg N kg−1, the BMP treatment significantly decreased exchangeable NH4+ and significantly increased total fixed NH4+ in all soils especially two clayey, vermiculitic soils. On the average of all soils applied 1000 mg N kg−1, the increase in total fixed NH4+ explained 55% of the decrease in exchangeable NH4+, and the decrease in exchangeable NH4+ was almost equal to the increase in nonexchangeable 15N. The rest of the NH4+ unaccounted by the fixation was partly due to the transformation of exchangeable NH4+ to hot KCl-extractable organic N, because the content of hot KCl-extractable organic N was significantly increased by the BMP treatment. In conclusion, the milling treatment prior to the analysis of fixed NH4+ in soils might cause either underestimation or overestimation depending on the content of exchangeable NH4+.

Competition for nitrogen between trees in a mixed-species plantation in the Solomon Islands

ABSTRACTAs part of an ACIAR project aiming at improving community forestry in Solomon Islands, mixed-species plantations were established to assess the feasibility of inter-planting teak (Tectona grandis L. f.) and flueggea (Flueggea flexuosa Muell. Arg). Flueggea is a native hardwood used for timber and fence construction, and early removal of flueggea from a mixed-species stand could have a similar silvicultural outcome to thinning a single-species stand of teak. Using 15N-labelled ammonium sulphate, we investigated the competition for nitrogen (N) between the two species. The 15N-labelled tracer was applied to the soil surface of plots containing pairs of trees, one of each species, in 2-year-old and 4-year-old mixed-species stands, after the pairs of trees were isolated from the rest of the stand by an impermeable membrane. After 12–18 months, the isolated trees were measured and harvested, and each tree component (roots, stem, branch and foliage) was weighed and analysed for total N and 15N enrichment. There was no significant difference in the amounts of 15N between teak and flueggea components at either age, suggesting equal uptake of added 15N-labelled tracer by both species. The 15N amount was greater in stem followed by root, foliage and branch for teak and branch followed by stem, root and foliage for flueggea. About 42% and 55% of the applied 15N tracer were recovered in the 2-year and 4-year plots respectively, suggesting that higher uptake occurs with well-established root structure and that N losses decreased following canopy closure. The amount of total nitrogen was not significantly different between teak and flueggea components at age 2 and 4 years, and may indicate equal access to growth resources, and similar allocation. Although teak had significantly greater stem growth (height, basal area and volume) than flueggea in the 4-year plots, 15N uptake were similar to flueggea, which may mean that competition for growth resources was still minimal or that access to the resources was equal and growth rates differed between species.

Interaction of Different Wheat Genotypes and Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate Using 15N Isotope Tracing Techniques

ABSTRACTTo investigate the effect of applying 15N-labeled ammonium sulfate with or without a nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on fertilizer use efficiency and crop productivity of different wheat genotypes, a field trial was conducted at the Nuclear Agricultural Department’s farm of Iran in 2013–2014. The treatments included five wheat genotypes with different 13 C isotope discrimination and three fertilizer treatments, an unfertilized control, 15N-labeled ammonium sulfate, and 15N-labeled ammonium sulfate with DMPP in three replications. Soil samples were taken after 2, 4, and 6 weeks after sowing and also at harvest time. Results from 15N experiment showed that DMPP delayed nitrification of ammonium for 42 days. Genotypes with lower discrimination index had greater uptake of ammonium ions which led to increase crop yield and nitrogen fertilizer use efficiency. The results also suggested that the use of DMPP may not be beneficial in some fast growing wheat genotypes.

Influence of 15N-labeled ammonium sulfate and straw on nitrogen retention and supply in different fertility soils

Microbial immobilization/mineralization and mineral fixation/release of ammonium are important for N retention and supply. However, the rates of such processes vary among different fertility soils and fertilization management practices. Three long-term different fertilized soils were used to simulate a range in soil fertility level and incubated with different N amendments for 144 days. The dynamics of 15N derived from ammonium sulfate (AS) or straw in different soil N pools and the ammonium sulfate-N or straw-N retention and supply were studied. In the absence of straw, the amount of ammonium sulfate-N present as fixed ammonium was 1.1–3.5-fold higher than that present as soil microbial biomass N (SMBN), although ammonium sulfate-derived SMBN and its mineralization increased by increasing soil fertility level. Straw addition significantly (P < 0.05) enhanced the relative importance of the SMBN pool on ammonium sulfate-N retention and supply compared with the fixed ammonium-N pool, and the former exceeded the latter in higher fertility soils. Regardless of soil fertility levels, straw addition significantly blocked the release of ammonium sulfate-N from the fixed ammonium-N pool. The SMBN pool was more important in straw-N retention and supply than the fixed ammonium-N pool, confirming that straw-N cycling depended more on biotic processes. The percentage of mineralized ammonium sulfate-N or straw-N from SMBN was higher than that released from fixed ammonium, indicating the higher availability of SMBN. Generally, the mineral fixation/release of ammonium was the main process for mineral fertilizer N retention and supply in the low fertility soil with or without straw addition, whereas microbial immobilization/mineralization became the main process in the high fertility soil with straw addition. Our results gave insights on the ammonium sulfate-N or straw-N retention and supply in different fertility soils, providing suggestions for optimizing straw management and synchronizing N supply with crop demand.

Contribution of fertilizer nitrogen to the total nitrogen extracted by sugarcane under Brazilian field conditions

With the ordinance that prohibits sugarcane harvesting with prior burning of plantations in Brazil, sugarcane crops absorbs barely 20 % of the N-fertilizer applied. This low recovery is attributed, in part, to nitrogen (N) mineralization in plant straw, high microbial immobilization, and N losses in the soil-plant system, mainly, when sources containing urea are applied to the soil surface. To evaluate N contribution from fertilizer in the sugarcane compartments and total N extracted by plants during the first ratoon cycle, microplots were installed inside plots of sugarcane ratoons. We applied isotope 15N-labelled urea, ammonium sulfate and ammonium chloride (3 % 15N atoms) at the dose of 100 kg N ha−1. The soil in the study was classified as a Typic-Hapludox and the experimental design consisted of randomized complete block with four replicates. In addition nitrogen immobilization and mineralization rates was evaluated estimated by aerobic incubation during 20 weeks. Sugarcane residue was incorporated to soil and nitrogenous fertilizers applied to the surface as ammoniacal or amidic-N at 100 mg N kg−1. N sources showed the same efficiency as the results showed no difference for N contents in plant shoots obtained from treatment with N fertilization. The use of ammonium chloride resulted in greater accumulation of N fertilizer in stalks at 218 days after fertilization. The percentage of N fertilizer was approximately 60 % in the early developmental stages, decreasing to 20 % near the harvesting stage. The addition of N-fertilizer in soils covered by sugarcane residue leads to immobilization of available-N in the soil.

Fungi prey on insects to feed plants

Although most plants obtain N from N-fixing bacteria, a recent paper describes how the soil fungi Metarhizium spp. act as vectors to shuttle insect-derived N to two common plant species. In addition to forming endophytic associations with many plant species, Metarhizium spp. are pathogens of a large number of insects. Because insects are a rich N source, the authors assessed whether Metarhizium robertsii delivers N to plants by obtaining this nutrient from its insect prey. The model insects, waxmoth larvae, were injected with a 15N-labelled ammonium sulphate solution and then introduced into soil microcosms containing the roots of either haricot bean or switchgrass. When the insects were infected with M. robertsii before introduction into the soil, up to 48% of the plant N was labelled, indicating that it was insect derived. By contrast, significantly less 15N was detected in plants associated with uninfected larvae. It is not yet known how widespread this phenomenon is, but the abundance of Metarhizium spp. in the wild would suggest that this is a common mechanism of N cycling in the soil.

Distribuição do Nitrogênio do Sulfato de Amônio (15N) no sistema solo-planta, em uma sucessão de culturas, sob sistema plantio direto

O aproveitamento do N pelo milho (Zea mays, L.) é influenciado pelas doses de adubo nitrogenado. O presente trabalho foi desenvolvido em um solo de textura arenoargilosa (Hapludox) e teve por objetivo avaliar a eficiência de utilização do N pela cultura de milho, em uma sucessão de culturas, utilizando-se sulfato de amônio marcado com 15N (5,5 átomos %), em diferentes doses; e o efeito residual desse fertilizante nas duas culturas subsequentes em sucessão (braquiária e milho), sob sistema plantio direto. As avaliações foram feitas em dois cultivos de milho safrinha - o primeiro no ano agrícola 2006 e o segundo em 2007 - e um de braquiária na entressafra. Os tratamentos consistiram de doses de N de 60, 120 e 180 kg ha-1, na forma de sulfato de amônio marcado (15N). Esse adubo foi aplicado em subparcelas, previamente definidas, apenas no primeiro cultivo do milho (safra 2006). Foram avaliados: N-total acumulado; N nas plantas de milho e braquiária proveniente do fertilizante, N no solo proveniente do fertilizante e recuperação de N-fertilizante pelas plantas e pelo solo. O maior aproveitamento do N-fertilizante pelo milho foi obtido no tratamento com 120 kg ha-1 de N, e o maior efeito residual do N-fertilizante pela braquiária e milho subsequente, no tratamento com 180 kg ha-1 de N. Após a sucessão de culturas, a recuperação de N pelo solo foi de 32, 23 e 27 % para os tratamentos com 60, 120 e 180 kg ha-1 de N.

Nitrogen-15 labeling and nitrogen transformation in silage maize-cattle manure system

¹⁵N示踪技术已开始应用于畜禽粪便氮素循环与利用研究领域, 而¹⁵N在畜禽粪便不同组分和不同形态氮素中的丰度与数量将直接影响到畜禽粪便¹⁵N示踪去向与氮素实际去向的一致性。为了解¹⁵N在畜禽粪便标记过程的转化特点和在标记粪尿的分布特征, 本文首先采用改进的、含有¹⁵N标记硫酸铵(60 atom% ¹⁵N)的Hoagland营养液砂培种植¹⁵N玉米, 然后将¹⁵N玉米和普通玉米以55∶45的氮配比作为混合青贮饲料饲喂１头已空腹2 d的2龄黄牛, 饲喂4 d后停喂2 d, 收集全部牛粪尿并对其不同组分和形态氮素的¹⁵N丰度和数量进行分析。结果表明: 标记玉米、混合青贮饲料、牛粪尿的¹⁵N丰度分别为48.024%、26.579%和8.044%; 标记玉米对硫酸铵¹⁵N的回收率为26.3%, 牛粪尿对标记玉米¹⁵N回收率为36.0%。在收集的牛粪尿氮中, 牛粪全氮、牛尿全氮、牛粪铵态氮和牛尿铵态氮量分别占70.25%、29.75%、5.44%和0.03%, 其¹⁵N丰度分别为9.223%、5.261%、6.505%和5.419%。在短期内通过饲喂黄牛¹⁵N青贮饲料制备的标记牛粪尿中, ¹⁵N丰度在不同组分和形态氮素中的分布并不相同, 牛尿氮的¹⁵N丰度低于牛粪氮, 矿质态和易于矿化态氮的¹⁵N丰度低于不易矿化态氮。

Low-temperature Nitrogen Uptake and Use of Three Cool-season Turfgrasses under Controlled Environments

Fall fertilization of turfgrass in northern climates is often considered to be agronomically beneficial, although research on nitrogen (N) uptake during cold temperatures is sparse and environmental concerns exist regarding nitrate leaching. Therefore, the objective of this study was to evaluate N uptake potential, use, and plant metabolic response in a climate-controlled environment evaluating the responses of various cool-season turfgrass species to variable N rates and temperature regimens. Creeping bentgrass (Agrostis stolonifera L.), kentucky bluegrass (Poa pratensis L.), and annual bluegrass (Poa annua var. reptans L.) were seeded and grown for 3 months and then acclimated in a growth chamber to one of three climate regimens corresponding to 15 Sept., 15 Oct., and 15 Nov. in Madison, WI. Grasses were fertilized at 0, 25, 49, or 98 kg·ha−1 N with 15N-labeled ammonium sulfate (10 atom % 15N) by applying a liquid solution of 75 mL per pot (1 cm of solution in depth). Data collected included verdure biomass, root mass, net canopy photosynthesis, and 15N fertilizer uptake. For all turfgrass species, shoot growth increased in response to N application in the September regimen, but not in October or November regimens. N uptake was significantly lower in the November regimen compared with September with an average of 73% of fertilizer recovery in September compared with 57% and 38% in October and November, respectively. Root mass and net canopy photosynthesis were greatest in the November treatments, although these responses were generally unaffected by N application rate. The results of this study indicate that N uptake capacity is greatly reduced as average daily temperatures approach 0 °C. Nitrogen application rates should be adjusted downward to maximize uptake efficiency in cold temperatures.

Incorporation of lysine from microbial origin into tissue protein of Iberian and Landrace × Large White piglets

The distinct incorporation of lysine from microbial origin in tissues has been investigated in Iberian and Landrace × Large White piglets of 47 ± 3 d of age ( n = 8/genotype) given 15N-labelled ammonium sulphate added to the diet. Four piglets of each breed were allocated in metabolic cages to prevent coprophagy. All piglets consumed the labelled diet for 10 days and then were slaughtered. Viscera and carcass weights were recorded and gastrointestinal tissues carefully handled. Samples of carcass, liver, and bacterial pellets isolated from the last third of the small intestine, were hydrolyzed, desalted by ion-exchange, and the amino acids eluted analyzed for 15N-lysine enrichment in a GC-combustion/isotope ratio mass-spectrometer. Background 15N-lysine in tissues was also determined in 3 piglets per breed. Liver enrichment was considerably higher in Landrace × Large White than in Iberian piglets (0.0273 ± 0.0013 vs. 0.0167 ± 0.0013 APE, P < 0.05) that, opposite to our expectations, suggests higher incorporation of microbial lysine in tissues of Landrace × Large White piglets. Protein shortage in the experimental diet relative to requirements could have enhanced microbial lysine absorption in the conventional piglets.

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Fate of 15N after combined application of rabbit manure and inorganic N fertilizers in a rice–wheat rotation system

The present study was carried out on pot experiments with rice (Oryza sativa L. cv. Wuyujing 7) and winter wheat (Triticum aestivum L. cv. Yangmai 6) rotation in a sandy and a clayey soil fertilized with 15N-labeled ammonium sulfate (AS) and 15N-labeled rabbit feces so as to study the mechanisms of reduction of fertilizer N loss by organic fertilizers. The treatments included: (1) control without any N fertilizer application; (2) fertilization with 15N-labeled AS (IF); (3) fertilization with labeled rabbit feces (OF); (4) fertilization with either 40% 15N-labeled rabbit feces and 60% unlabeled AS (IOF1) or (5) 40% unlabeled rabbit feces and 60% 15N-labeled AS (IOF2). In the rice season, the IOF treatments compared to the IF treatment decreased the percentage of lost fertilizer N from the sandy and clayey soils, whereas it increased the percentage of fertilizer N, present as mineral N and microbial biomass N (MBN). During the second season, when soils were cropped to winter wheat, the IOF treatments in comparison with the IF or OF treatment increased mineral N and MBN contents of soils sampled at tillering, jointing, and heading stages, and such increases were derived from the organic N fertilizer in the sandy soil and from the inorganic N fertilizer in the clayey soil. The increased MBN in the IOF treatments was derived from inorganic fertilizers applied both soils. Therefore, in the IOF treatment, during the rice season, the organic N increased the immobilization of inorganic N in MBN, while the inorganic N fertilizer applied to both soils stimulated the uptake of organic N and the organic N fertilizer increased the uptake of inorganic N by winter wheat; the inorganic N increased the recovery of organic N in the plant-soil system after harvesting the winter wheat.

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Abstracts of Nippon Dojo-Hiryogaku Zasshi