土壤碳氮比对平邑甜茶幼苗生长和碳氮分配的影响

为探讨土壤碳氮比(C:N)对苹果(Malus pumila)植株生长和碳氮分配特性的影响, 采用碳氮双标记示踪技术, 以二年生平邑甜茶(Malus hupehensis)幼苗为试验材料, 研究了6个不同土壤C:N处理(T1-T6分别为4.70、9.78、14.70、19.96、25.60和28.83)下平邑甜茶的生长状况和氮素吸收、利用分配以及碳水化合物的运转特性。结果表明, 随着土壤C:N的逐渐增大, 平邑甜茶幼苗根系干重逐渐增加, 而株高、茎粗、地上部干重和植株总干重呈先增加后降低的趋势, 以T4处理最大。土壤C:N显著影响了平邑甜茶幼苗的 ¹⁵N利用率, 从T1到T4处理, 植株的 ¹⁵N利用率逐渐升高, T4处理(18.46%)是T1处理(10.65%)的1.73倍; 随着土壤C:N的进一步增加, 植株的 ¹⁵N利用率逐渐降低, T5和T6处理分别比T4处理降低了1.59%和2.58%。土壤C:N较低的T1和T2处理, 平邑甜茶幼苗各器官从肥料中吸收分配到的 ¹⁵N量对该器官全氮量的贡献率(Ndff)大小顺序为根>叶>茎, 随着土壤C:N的进一步增大, 叶片的Ndff均为最大, 其次是根, 茎最少。随着土壤C:N的增大, 叶片 ¹⁵N分配率逐渐升高, ¹³C分配率逐渐降低; 而根系 ¹⁵N分配率逐渐降低, ¹³C分配率逐渐升高。综合考虑植株生长和氮素利用状况, 本试验条件下适宜平邑甜茶生长的土壤C:N为21-23。     

氮磷添加对荒漠草原植物-凋落物-土壤生态化学计量特征的影响

为明确植物、凋落物和土壤养分含量及化学计量比对土壤中添加多种限制性养分的响应,阐明“植物-凋落物-土壤”连续体化学计量动态及各组分之间的协同作用,以宁夏荒漠草原为研究对象,于2018年开始进行氮(N)、磷(P)养分添加控制试验。试验处理包括对照(CK)、N添加、P添加、NP共同添加4个处理。结果表明：(1)NP共同添加显著增加了荒漠草原植物N和P含量、以及凋落物和土壤P含量,显著降低了荒漠草原植物C∶N和C∶P、以及土壤和凋落物C∶P和N∶P。P添加显著增加了荒漠草原植物、凋落物和土壤P含量,显著降低了植物、凋落物、土壤C∶P和N∶P。N添加分别增加了植物、凋落物N含量和N∶P,但对植物N含量影响未达到显著水平。(2)C、N、P含量和N∶P大小均表现为植物>凋落物>土壤,C∶N和C∶P均表现为凋落物>植物。(3)N添加提高了荒漠草原植物对P再吸收效率,降低了荒漠草原植物对N利用效率;P添加提高荒漠草原植物对N再吸收效率,降低荒漠草原对P的利用效率;NP共同添加提高了荒漠草原植物对N和P再吸收效率,降低了荒漠草原植物对N和P利用效率。(4)植物-凋落物-土壤的N、P含量...     

Modeling forest stand dynamics from optimal balances of carbon and nitrogen

We formulate a dynamic evolutionary optimization problem to predict the optimal pattern by which carbon (C) and nitrogen (N) are co-allocated to fine-root, leaf, and wood production, with the objective of maximizing height growth rate, year by year, in an even-aged stand. Height growth is maximized with respect to two adaptive traits, leaf N concentration and the ratio of fine-root mass to sapwood cross-sectional area. Constraints on the optimization include pipe-model structure, the C cost of N acquisition, and agreement between the C and N balances. The latter is determined by two models of height growth rate, one derived from the C balance and the other from the N balance; agreement is defined by identical growth rates. Predicted time-courses of maximized height growth rate accord with general observations. Across an N gradient, higher N availability leads to greater N utilization and net primary productivity, larger trees, and greater stocks of leaf and live wood biomass, with declining gains as a result of saturation effects at high N availability. Fine-root biomass is greatest at intermediate N availability. Predicted leaf and fine-root stocks agree with data from coniferous stands across Finland. Optimal C-allocation patterns agree with published observations and model analyses.     

Effect of low-protein corn and soybean meal-based diets on nitrogen utilization,litter quality,and water consumption in broiler chicken production: insight from meta-analysis

The growing demand for high-value animal protein must be met using sustainable means that optimize the utilization of nutrients, especially nitrogen (N) so that excreta do not over-fertilize fields and end up causing soil acidification, waterway eutrophication and greenhouse gas emissions. Malodorous N compounds can cause respiratory diseases and poor growth in livestock. The increasing availability of feed-grade amino acids makes it possible to formulate low-protein diets for broilers and thereby reduce N excretion. However, published studies of the effects of such diets on broiler growth performance have been based on reducing CP contents gradually in a variety of ways that have given inconsistent results. Since the amount of published data is now large, a meta-analysis was performed in order to categorize diet formulation strategies and quantify their impact on N balance, water consumption, litter moisture, plasma uric acid. This showed that lowering the CP content of broiler diets generally means replacing some soybean meal with corn and hence increasing the starch content. However, since soybean meal is also a source of potassium, this reduces electrolyte balance. Lowering the CP content from 19% to 17% is associated with a 29% reduction of N excretion in broilers aged 0–21 d, and a 7% increase in N efficiency (N retention/N intake). Reducing the CP content from 19% to 17% decreases daily water consumption by 20.6 mL/bird, litter moisture by 2.2% and plasma uric acid by 0.56 mg/dL. This meta-analysis improves our understanding of the low-protein strategy and allows us to quantify its impact on N balance, litter quality and uric acid. It shows that managing N excretion is wholly beneficial and reduces litter wetness.     

Strategies for optimizing nitrogen use by ruminants

The efficiency of N utilization in ruminants is typically low (around 25%) and highly variable (10% to 40%) compared with the higher efficiency of other production animals. The low efficiency has implications for the production performance and environment. Many efforts have been devoted to improving the efficiency of N utilization in ruminants, and while major improvements in our understanding of N requirements and metabolism have been achieved, the overall efficiency remains low. In general, maximal efficiency of N utilization will only occur at the expense of some losses in production performance. However, optimal production and N utilization may be achieved through the understanding of the key mechanisms involved in the control of N metabolism. Key factors in the rumen include the efficiency of N capture in the rumen (grams of bacterial N per grams of rumen available N) and the modification of protein degradation. Traditionally, protein degradation has been modulated by modifying the feed (physical and chemical treatments). Modifying the rumen microflora involved in peptide degradation and amino acid deamination offers an alternative approach that needs to be addressed. Current evidence indicates that in typical feeding conditions there is limited net recycling of N into the rumen (blood urea-N uptake minus ammonia-N absorption), but understanding the factors controlling urea transport across the rumen wall may reverse the balance to take advantage of the recycling capabilities of ruminants. Finally, there is considerable metabolism of amino acids (AA) in the portal-drained viscera (PDV) and liver. However, most of this process occurs through the uptake of AA from the arterial blood and not during the 'absorptive' process. Therefore, AA are available to the peripheral circulation and to the mammary gland before being used by PDV and the liver. In these conditions, the mammary gland plays a key role in determining the efficiency of N utilization because the PDV and liver will use AA in excess of those required by the mammary gland. Protein synthesis in the mammary gland appears to be tightly regulated by local and systemic signals. The understanding of factors regulating AA supply and absorption in the mammary gland, and the synthesis of milk protein should allow the formulation of diets that increase total AA uptake by the mammary gland and thus reduce AA utilization by PDV and the liver. A better understanding of these key processes should allow the development of strategies to improve the efficiency of N utilization in ruminants.     

The superior nitrogen efficiency of winter oilseed rape (Brassica napus L.) hybrids is not related to delayed nitrogen starvation-induced leaf senescence

Aims

Winter oilseed rape (Brassica napus L.) cultivation causes high nitrogen (N) balance surpluses. The breeding and cultivation of N-efficient cultivars (high grain yield under low N supply) can contribute to the reduction of the crop-specific N surpluses. Comparing line cultivars with hybrids and dwarfs the hypothesis was tested if stay-green into reproductive growth contributes to superior N efficiency of hybrids and dwarfs.

Methods

The present work comprised two years field experiments with ten line, five hybrid and three dwarf cultivars and hydroponic experiments with three hybrid and nine line cultivars.

Results

Hybrids were superior in yield formation independent of the N supply. The greater N efficiency of the hybrids was related to a higher N uptake until maturity, but not to stay-green. This was in agreement with a hydroponic experiment in which the hybrids were particularly responsive in N starvation-induced leaf senescence of older leaves as revealed by SPAD, photosynthesis and the expression of the senescence-specific cysteine protease gene SAG12-1. Additionally, hybrids were characterized by an efficient N retranslocation from vegetative to reproductive plant organs in combination with a lower grain-N concentration.

Conclusions

Both, N uptake and N utilization efficiency were decisive for the superior N efficiency of the hybrids.     

Diet-switching by gypsy moth: effects of diet nitrogen history vs. switching on growth, consumption, and food utilization

Gypsy moth (Lymantria dispar (L.) (Lepidoptera: Lymantriidae)) larvae were reared from hatch on 1.25% N or 3.5% N artificial diet (previous diet) and switched reciprocally to the other diet (current diet) after molting into the second, third, fourth, or fifth instar. The nitrogen concentration of food consumed during previous instars had a strong residual effect on the growth rate in subsequent instars when a diet switch was made during instars two through four, but did not affect growth rate of fifth-instar larvae despite effects on food consumption and utilization. In early instars, larvae reared on 1.25% N artificial diet and then switched to 3.75% N diet had lower mass-adjusted growth rates than larvae continuously reared on 3.75% N diet. Conversely, larvae reared on 3.75% N diet and switched to 1.25% N had higher mass-adjusted growth rates than larvae reared continuously on 1.25% N diet. Relative to larvae previously reared on 1.25% N diet, fifth-instar male larvae previously reared on 3.75% N diet had slightly lower consumption rates, higher net growth efficiency (ECD), and higher gross growth efficiency (ECI). Larvae previously reared on 3.75% N diet tended to have lower food assimilation efficiency (AD) and lower nitrogen assimilation efficiency (AD(N)). Although both previous and current diet nitrogen concentration strongly affected larval growth and food utilization, the interaction term between these was not significant for any response variables except ECD and ECI. Because the interaction term reflects the effect of switching per se, the results indicate that there was a metabolic cost associated with switching, but no inherent net cost or benefit of diet-switching to growth.     

Effects of food quality,particularly nitrogen concentrations,of Eucalyptus blakelyi foliage on the growth of Paropsis atomaria larvae (Coleoptera: Chrysomelidae)

Five groups of E. blakelyi seedlings were differentially fertilized to obtain a range of N concentrations from 0.8–3.0% dry wt in the foliage. Groups of P. atomaria larvae were reared from eclosion to the prepupal stage on these seedlings. The effects on larval growth and development caused by foliar concentrations of N, moisture content, and tannins and leaf toughness were measured. Pupal dry weight and development time of P. atomaria did not differ between those reared on foliage with N levels of 1.7–3.0% but there was a significant decrease in pupal weight and increase in development time for individuals fed foliage with N below this level. Larvae fed foliage with an average of 0.8% N died before reaching instar III. Total dry matter consumption increased with a decrease in N concentration. Larval nitrogen utilization efficiency increased as foliar N level decreased until N reached a level somewhere between 1.7%–1.2% below which it decreased. There appeared to be an N concentration threshold above which P. atomaria larvae received adequate N by regulating consumption and nitrogen utilization efficiency but below which they could no longer accumulate enough N by compensation to maintain an optimum growth rate and development time. Effects of food quality variables on relative growth and consumption rates are presented and discussed.     

The effect of cropping and fertiliser nitrogen rates on nitrogen balance in soil

Summary Fertilizer/soil N balance of cropped and fallow soil has been studied in a pot experiment carried out with grey forest soil (southern part of Moscow region) at increasing rates of¹⁵N labelled ammonium sulfate (0; 8; 16; 32 mg N/100 g of soil). The fertilizer¹⁵N balance has been shown to depend upon its application rate and the presence of growing plants. Fertilizer N uptake efficiency was maximum (72.5%) and gaseous losses-minimum (12.5%) at the application rate of 16 mg N/100 g of soil. Fertilizer N losses from the fallow soil were 130–220% versus those from the cropped soil. At the application of fertilizer N the plant uptake of soil N was 170–240% and the amount of soil N as N–NH₄ exchangeable + N–NO₃ in fallow was 350–440% as compared to the control treatment without nitrogen (PK).After cropping without or with N fertilizer application at the rates of 8 and 32 mg N/100 g of soil, a positive nitrogen balance has been found which is likely due to nonsymbiotic (associative) N-fixation. It has been shown that biologically fixed nitrogen contributes to plant nutrition.     

富士苹果萌芽至新梢旺长期肥料氮去向和土壤氮库盈亏

运用¹⁵N同位素示踪技术,以5年生‘烟富3’/SH6/平邑甜茶苹果为试材,研究了萌芽至新梢旺长期不同施氮水平(0、50、100、150、200、250 kg·hm^-2)下肥料氮的吸收利用、土壤残留和土壤氮库盈亏特点.结果表明:早春施氮后,15N均优先分配到根系中,然后转运用于地上部新生器官(果实、新生枝叶)的形态建造.新梢旺长期结束后(施氮2个月后),5.9%~9.9%的肥料氮被树体吸收,29.8%~33.4%的肥料氮残留在0~60 cm土体中,56.7%~64.4%的肥料氮通过其他途径损失.随施氮水平的提高,树体吸收的肥料氮量和土壤残留氮量逐渐增加,但肥料氮利用率和土壤残留率却不断降低,同时损失量和损失率不断增加.随施氮水平的提高,土壤氮素总平衡由亏缺转为盈余,且盈余量随施氮水平的提高而显著提高.表明施氮不足将会造成土壤氮肥力的下降;而过量施氮则会加剧土壤氮素累积,增加氮素污染风险.施氮水平与土壤氮素总平衡呈显著线性相关关系,拟合方程为:y=0.3511x-20.808(R^2=0.9927),当施氮量为59.27 kg·hm^-2时,由萌芽至新梢旺长期的土壤氮库达到平衡.     

氮肥调控剂对潮褐土中不同氮源氮素转化及油菜生长的影响

采用土壤培养和盆栽试验相结合的方法,研究了硝化抑制剂双氰胺(DCD)与纳米碳配合施用对尿素和碳酸氢铵在华北平原典型土壤潮褐土中转化的调控效果及其对油菜生长的影响.结果表明:尿素和碳酸氢铵在施入土壤后的2周内,土壤无机氮的供应强度差别较大,2周以后则基本相似.2种氮源对油菜生长及氮素利用的影响在生育前期(播种后34 d)差异显著,但最终达到商品生物量收获时,氮源之间差异不大.DCD对尿素和碳酸氢铵在潮褐土中的转化表现出显著的硝化抑制作用,其抑制强度和有效抑制时间随DCD用量的增加而增强,且以对碳酸氢铵施入土壤后的硝化抑制效果更好.在本研究条件下,DCD用量以占肥料纯氮量的1.0％ ～1.5％相对较佳,可显著提高油菜产量,改善叶色,降低植株硝酸盐含量,提高氮肥利用率.纳米碳与DCD配合施用对土壤铵氧化有明显的协同抑制效果,且可以显著刺激油菜前期的生长发育和氮素利用,降低油菜硝酸盐含量.     

氮肥调控剂对潮褐土中不同氮源氮素转化及油菜生长的影响

采用土壤培养和盆栽试验相结合的方法,研究了硝化抑制剂双氰胺(DCD)与纳米碳配合施用对尿素和碳酸氢铵在华北平原典型土壤潮褐土中转化的调控效果及其对油菜生长的影响.结果表明： 尿素和碳酸氢铵在施入土壤后的2周内,土壤无机氮的供应强度差别较大,2周以后则基本相似.2种氮源对油菜生长及氮素利用的影响在生育前期(播种后34 d)差异显著,但最终达到商品生物量收获时,氮源之间差异不大.DCD对尿素和碳酸氢铵在潮褐土中的转化表现出显著的硝化抑制作用,其抑制强度和有效抑制时间随DCD用量的增加而增强,且以对碳酸氢铵施入土壤后的硝化抑制效果更好.在本研究条件下,DCD用量以占肥料纯氮量的1.0%～1.5%相对较佳,可显著提高油菜产量,改善叶色,降低植株硝酸盐含量,提高氮肥利用率.纳米碳与DCD配合施用对土壤铵氧化有明显的协同抑制效果,且可以显著刺激油菜前期的生长发育和氮素利用,降低油菜硝酸盐含量.     

减氮配施稻秆生物炭对稻田土壤养分及植株氮素吸收的影响

通过2018年早稻和晚稻田间试验,研究化学氮肥减量及配施稻秆生物炭对稻田土壤养分特性及植株氮素吸收的影响。试验包括6个处理:不施氮(CK)、常规施氮(N₁₀₀)、减氮20%(N₈₀)、减氮20%配施生物炭(N₈₀+BC)、减氮40%(N₆₀)、减氮40%配施生物炭(N₆₀+BC)。结果表明: 与常规施氮相比,单纯减氮20%和40%或配施生物炭对早晚稻不同生育期土壤pH、有机质、全氮、铵态氮、全磷、有效磷、全钾、速效钾无显著影响;减氮20%配施生物炭显著增加晚稻分蘖期的土壤阳离子交换量(CEC),而减氮40%配施生物炭则显著增加晚稻抽穗期的电导率(EC)值。与单纯减氮相比,N₈₀+BC的土壤速效钾含量在早晚稻抽穗期均显著升高,土壤pH值、全氮在晚稻成熟期显著增加;N₆₀+BC的土壤全钾含量在早稻成熟期显著升高。不同处理早稻土壤硝态氮含量随生育进程逐渐降低,与分蘖期相比,抽穗期和成熟期的常规施氮土壤硝态氮含量分别降低50.0%和71.6%,而配施生物炭处理则降低6.3%～45.5%,减氮配施生物炭显著降低了硝态氮的流失。在晚稻抽穗期,减氮配施生物炭植株吸氮量显著高于常规施氮和单纯减氮,增加幅度为34.8%～52.4%。综上,适度的减氮或配施稻秆生物炭能有效保持土壤养分,促进水稻对氮素的吸收,提高氮素利用率。     

氮添加对森林植物磷含量的影响及其机制

氮沉降对森林生态系统磷循环产生了不可忽视的影响, 尤其是加剧了植物生长的磷限制, 从而使得氮沉降背景下植物磷含量变化备受关注。该文综述了氮添加对森林植物磷含量的影响, 认为氮添加通过促进土壤磷酸酶活性进而提高土壤有效磷含量, 有利于植物的磷吸收并增加植物磷含量。同时, 森林植物磷含量对氮添加的响应还受物种、生活型以及施氮时间长短等因素的影响。基于森林植物磷含量对氮添加响应的差异性, 该文进一步探讨氮富集背景下森林植物磷含量变化的可能机制: 1)外源氮输入通过改变土壤中有效磷含量从而对植物磷的来源产生影响; 2)通过影响植物的根系分泌物、菌根共生和根系形态结构等进而影响植物的磷吸收能力; 3)通过影响植物的磷养分再分配、磷养分重吸收对植物磷利用效率产生影响。综上所述, 外源氮输入使植物磷含量发生改变, 首要原因是土壤有效磷含量的改变, 其次是植物磷吸收能力和磷利用效率的改变起调控作用。     

Modelling developmental changes in the carbon and nitrogen budgets of larval brachyuran crabs

The uptake and partitioning of nutritional carbon (C) and nitrogen (N) were studied during the complete larval development of a brachyuran crab,Hyas araneus, reared under constant conditions in the laboratory. Biochemical and physiological data were published in a foregoing paper, and complete budgets of C and N were now constructed from these data. Regression equations describing rates of feeding (F), growth (G), respiration (R), and ammonia excretion (U) as functions of time during individual larval moult cycles were inserted in a simulation model, in order to analyse time-dependent (i.e. developmental) patterns of variation in these parameters as well as in bioenergetic efficiencies. Absolute daily feeding rates (F; per individual) as well as carbon and nitrogen-specific rates (F/C, F/N) are in general maximum in early, and minimum in late stages of individual larval moult cycles (postmoult and premoult, respectively). Early crab zoeae may ingest equivalents of up to ca 40% body C and 30% body N per day, respectively, whereas megalopa larvae usually eat less than 10%. Also growth rates (G; G/C, G/N) reveal decreasing tendencies both during individual moult cycles and, on the average, in subsequent instars. Conversion of C and N data to lipid and protein, respectively, suggests that in all larval instars there is initially an increase in the lipid: protein ratio. Protein, however, remains clearly the predominant biochemical constituent in larval biomass. The absolute and specific values of respiration (R; R/C) and excretion (U; U/N) vary only little during the course of individual moult cycles. Thus, their significance in relation toG increases within the C and N budgets, and net growth efficiency (K ₂) decreases concurrently. Also gross growth and assimilation efficiency (K ₂; A/F) are, in general, maximum in early stages of the moult cycle (postmoult). Biochemical data suggest that lipid utilization efficiency is particularly high in early moult cycle stages, whereas protein utilization efficiency is higher in later stages. Only the zoea II appears to accumulate lipid from food constantly with a higher conversion efficiency than protein. The cumulative C and N budgets show in subsequent larval instars conspicuously increasing figures in all of their parameters.F andG increase to a particularly high extent from the first to the second zoeal instar, whereasR, U, exuvia production (G _E), and total assimilation (A) reveal a greater increase from the zoea II to the megalopa. Respiratory, excretory, and exuvial losses increase in subsequent larval instars at higher rates than tissue growth and, hence,K ₂ decreases in the same order. In the C budget,K ₂ values of 0.63 (zoea I). 0.56 (zoea II), and 0.29 (megalopa) were calculated (or: 0.56, 0.46, and 0.16 after subtraction of exuviae). In the N budget, corresponding values of 0.76, 0.66, and 0.45 (or: 0.72, 0.62, 0.38 without exuviae) were obtained. AlsoK ₁ decreases slightly in subsequent instars, whereasA/F reveals rather an increasing tendency, at least from the zoeal instars to the megalopa. Changes in the uptake and partitioning of matter in crab larvae are discussed in relation to developmental events and changes in life style before metamorphosis.     

嫁接与施氮对甜瓜产量和氮素吸收、利用的影响

通过裂区设计田间试验,主区为2种栽培方式(嫁接栽培和自根栽培),副区为4个施氮水平(0、120、240、360 kg N·hm^-2),研究了栽培方式和施氮量对甜瓜产量和品质、氮素运移和分配,以及氮素利用率的影响.结果表明: 嫁接栽培的甜瓜商品瓜产量较自根甜瓜提高了7.3%,可溶性固形物含量降低了0.16%～3.28%;生长前期嫁接栽培甜瓜氮素累积量较自根栽培低,结果后嫁接栽培氮素累积量显著升高,收获时植株氮素累积量较自根栽培增加了5.2%,果实中的氮素累积量提高了10.3%;嫁接栽培植株氮素向果实的转移量较自根栽培提高了20.9%,嫁接栽培果实中的氮素分配率在80%以上,自根栽培的分配率在80%以下;在同一施氮水平下,嫁接栽培的甜瓜氮素吸收利用率较自根栽培提高了1.3%～4.2%,氮素农学效率提高了2.73～5.56 kg·kg^-1,氮素生理利用率提高了7.39～16.18 kg·kg^-1;从商品瓜产量、氮素吸收量和氮素利用率综合考虑,施氮量240 kg·hm^-2为本区域嫁接甜瓜较适宜的氮素用量.     

施氮和肥料添加剂对水稻产量、氮素吸收转运及利用的影响

在苏南太湖地区开展田间试验,研究了施氮和肥料添加剂对水稻产量、氮素吸收转运及利用的影响.结果表明:施氮对水稻产量、各生育时期植株累积吸氮量、阶段氮累积量和花后氮素转运量具有显著的促进作用(P＜0.01),当施氮量高于200 kg·hm-2时,增施氮肥的增产效应不显著(P＞0.05);花后氮素转运率和氮肥利用率均随施氮量的增加而降低.施用肥料添加剂可进一步提高水稻产量、累积吸氮量、花后氮素转运量和氮肥利用率,且该效应在高施氮量( ≥200 kg·hm-2)条件下表现更明显.本试验条件下不施用肥料添加剂时,施氮150kg·hm-2可同时获得较高的产量和氮肥利用率.     

Phosphorus use efficiency and nitrogen balance of cowpea breeding lines in a low P soil of the derived savanna zone in West Africa

Differences in growth, nodulation and arbuscular mycorrhizal fungi (AMF) root infection among recent cowpea breeding lines from IITA were examined at low and high P levels in pot (94 lines) and field experiments (43 lines) at Fashola in the derived savanna zone of Nigeria. Based on their growth performance, these lines were subdivided into 5 groups: (i) poor performance under low and high P conditions; (ii) good performance under low P and poor performance under high P; (iii) intermediate performance under high and low P; (iv) good performance under high and low P conditions; and (v) good performance under high P and poor performance under low P. About 42% of the breeding lines (18 out of 43 lines tested) had the same grouping for the field and pot experiments. Eight cowpea lines (4 P-responders and 4 non-P-responders) were selected from the first experiment for subsequent studies on the effect of P supply (0, 20, 40 and 60 kg P ha^-1) on P uptake, P use efficiency, dry matter production, N-fixation, AMF infection and N balance. Dry matter production, shoot/root ratio, total shoot N, and total N-fixed of the non-P-responder line, IT81D-715, were strongly related to P uptake efficiency. The P-responder IT81D-849 had a significant (95%) correlation between AMF and P-use efficiency. The cowpea lines fixed on average 22 kg N ha^-1, which was 70% of the plant total N. The N balance based on the difference between the amount of N₂ fixed and N exported through the harvest, ranged between −10.6 kg N ha^-1 and +7.7 kg N ha^-1. Based on its adaptability to grow in low P soils and overall positive N balance, the cowpea line IT81D-715 should be recommended for cultivation when P is the limiting factor. This revised version was published online in June 2006 with corrections to the Cover Date.     

Untersuchungen über die Anforderungen von Puten in Bodenhaltung an den Energie- und Rohproteingehalt des Mischfutters

Object of investigations was to estimate lysine efficiency from different lysine sources (lysinemonohydrochloride and lysinesulfate resp.) for rats, piglets and broiler chickens to reach a higher level of calculation of lysine supply. Lysine limiting diets were based on wheat, soybean meal and wheat gluten, supplemented with different levels of lysine sources under investigation. Balance trials (rat, piglet, chicken) and growth trails with analyses of body composition (chicken) were done to estimate N‐balance resp. N‐deposition. N‐utilization model from Gebhardt (1966) and its further developement for efficiency estimation of feed amino acids were used for data calculation. Results allow conclusion, that there are no differences in utilization of lysine from lysinemonohydrochloride and lysinesulfate. Limitations of efficiency resulting from differences in time course of absorption between protein bound and free lysine were not observed under ad lib. feeding conditions.