Nitrogen yield and nitrogen fixation of winter faba beans

Introducing autumn-sown legumes into Central European farming systems could be beneficial for addressing two challenges for European agriculture, i.e., the substantial deficit of protein sources for livestock and expected changes in agroclimatic conditions. Therefore, a two-year field experiment was conucted under Pannonian climate conditions in eastern Austria to assess nitrogen (N) yield and N fixation of several winter faba bean varieties from different European countries as compared to a spring faba bean. Winter wheat was used as a reference crop for estimating atmospheric N fixation. Winter faba beans were susceptible to frost damage especially in the harder of the two winters. Winter faba bean varieties could not achieve a higher grain yield and a higher grain N yield than the spring faba bean but had a higher grain N concentration (except for one variety). Grain yield and grain N yield of faba beans were severely impaired by drought in one year (with a mean of varieties of 8.3 g N m^?2, winter wheat: 6.4 g N m^?2); in the other year, grain N yield of faba beans considerably surpassed that of winter wheat (with a mean of varieties of 21.5 g N m^?2, winter wheat: 8.8 g N m^?2). After harvest, faba beans left higher nitrate residues in the soil, especially in the subsoil, and higher amounts of N in above-ground residues compared to winter wheat. Faba beans showed high N fixation under optimum conditions (with a mean of varieties of 21.9 g N m^?2) whereas drought considerably impaired N fixation (with a mean of varieties of 6.3 g N m^?2; with no differences between autumn- and spring-sown faba beans). In conclusion, growing winter faba bean varieties in eastern Austria did not result in higher grain yield, grain N yield, and N fixation compared to growing a spring faba bean.     

Wheat response to N2 fixed by faba bean (Vicia faba L.) as affected by sulfur fertilization and rhizobial inoculation in semi‐arid Northern Ethiopia

Nitrogen fixation in faba bean (Vicia faba cv. Mesay) as affected by sulfur (S) fertilization (30 kg S ha^–1) and inoculation under the semi‐arid conditions of Ethiopia was studied using the ¹⁵N‐isotope dilution method. The effect of faba bean–fixed nitrogen (N) on yield of the subsequent wheat crop (Triticum aestivum L.) was also assessed. Sulfur fertilization and inoculation significantly (p < 0.05) affected nodulation at late flowering stage for both 2004 and 2005 cropping seasons. The nodule number and nodule fresh weighs were increased by 53% and 95%, relative to the control. Similarly, both treatments (S fertilization and inoculants) significantly improved biomass and grain yield of faba bean on average by 2.2 and 1.2 Mg ha^–1. This corresponds to 37% and 50% increases, respectively, relative to the control. Total N and S uptake of grains was significantly higher by 59.6 and 3.3 kg ha^–1, which are 76% and 66% increases, respectively. Sulfur and inoculation enhanced the percentage of N derived from the atmosphere in the whole plant of faba bean from 51% to 73%. This corresponds to N₂ fixation varying from 49 to 147 kg N ha^–1. The percentage of N derived from fertilizer (%Ndff) and soil (%Ndfs) of faba bean varied from 4.3% to 2.8 %, and from 45.1% to 24.0%, corresponding to the average values of 5.1 and 47.9 kg N ha^–1. Similarly, the %Ndff and %Ndfs of the reference crop, barley, varied from 8.5 % to 10.8% and from 91.5% to 89.2%, with average N yields of 9.2 and 84.3 kg N ha^–1. Soil N balance after faba bean ranged from 13 to 52 kg N ha^–1. Beneficial effects of faba bean on yield of a wheat crop grown after faba bean were highly significant, increasing the average grain and N yields of this crop by 1.11 Mg ha^–1 and 30 kg ha^–1, relative to the yield of wheat grown after the reference crop, barley. Thus, it can be concluded that faba bean can be grown as an alternative crop to fallow, benefiting farmers economically and increasing the soil fertility.     

Limited winter survival and compensation mechanisms of yield components constrain winter faba bean production in Central Europe

A substantial deficit of protein sources for livestock and expected changes in agro-climatic conditions are two challenges for European agriculture. Both can be addressed by introducing more autumn-sown legumes into Central European farming systems. Therefore, a three-year field experiment was conducted under Pannonian climate conditions in eastern Austria in which several winter faba bean varieties from different European countries were compared to a spring faba bean variety. Winter faba bean was susceptible to frost damage. Best overwintering was observed with the German variety Hiverna and the French variety Diva. Regarding overwintering, the first winter allowed for a clear differentiation between varieties, in the second winter, severe frost caused loss of almost all winter faba bean plants and in the third winter, which was mild, most varieties showed good overwintering. Grain yield of winter faba bean was mainly determined by variations of plants m^?2 (i.e. by overwintering) whereas compensatory mechanisms between yield components had a minor influence on yield formation. No grain yield advantage could be observed for winter faba bean varieties compared to the spring faba bean variety even in the year with good overwintering. Regarding yield components, winter faba bean had generally more shoots plant^?1 and a higher thousand kernel weight but spring faba bean tended to have more pods shoot^?1 and grains shoot^?1 whereas pods plant^?1, grains plant^?1 and grains pod^?1 generally did not differ. In conclusion, limited winter hardiness together with the minor influence of compensatory mechanisms between yield components on yield formation are serious constraints for increasing the cultivation of winter faba bean in Central Europe.     

Growth,yield and yield components of dry bean as influenced by phosphorus in a tropical acid soil

Phosphorus (P) deficiency is one of the most yield limiting factors for dry bean (Phaseolus vulgaris) production in tropical acid soils. Dry beans are invariably grown as mono-crops or as inter-crops under the perennial tropical crops. Information is limited regarding the influence of phosphorus fertilization on dry bean yield and yield components and P use efficiency in tropical acid soils. A greenhouse experiment was conducted to evaluate the influence of phosphorus fertilization on dry bean growth, yield and yield components and P uptake parameters. Phosphorus rates used were 0, 50, 100, 150, 200, and 250 mg P kg^?1 of soil. Soil used in the experiment was an acidic Inceptisol. Grain yield, shoot dry weight, number of pods, and 100 grain weight were significantly (P < 0.01) increased with phosphorus fertilization. Maximum grain yield, shoot dry matter, number of pods, and 100 grain weight were obtained with the application of 165, 216, 162, and 160 mg P kg^?1 of soil, respectively, as calculated by regression equations. Grain yield was significantly and positively associated with shoot dry weight, number of pods, P concentration in grain and total uptake of P in shoot and grain. Phosphorus use efficiency defined in several ways, decreased with increasing P rates from 50 to 250 mg P kg^?1 of soil. Maximum grain yield was obtained at 82 mg kg^?1 of Mehlich 1 extractable soil P. Results suggest that dry bean yield in Brazilian Inceptisols could be significantly increased with the use of adequate rates of phosphorus fertilization.     

Determining the optimum range of soil Olsen P for high P use efficiency, crop yield, and soil fertility in three typical cropland soils

Soil Olsen P level has a major influence on crop yield, efficient P utilization, and soil fertility. In this study, the optimum Olsen P range was determined from long-term (1990-2012) field experiments in three typical soil types of China under single cropping of maize or double cropping of maize and wheat. The critical soil Olsen P value for crop yield was evaluated using three different models, and the relationships among P use efficiency (PUE), Olsen P, and total P were analyzed. The agronomic critical soil Olsen P values obtained from the three models for the neutral soil of Gongzhuling and the calcareous soil of Zhengzhou were similar; however, the values from the linear-linear and linear-plateau models for both maize and wheat were substantially lower than those from the Mitscherlich model for the acidic soil of Qiyang. The PUE response change rates (linear equation slopes) under different soil Olsen P levels were small, indicating slight or no changes in the PUE as the soil Olsen P increased in all three soils. A comparison of the Olsen P levels that achieved the maximal PUE with the agronomic critical values derived from the three models indicated that the linear-plateau model exhibited the best performance. The regression equation coefficients of Olsen P response to total P decreased as follows:Zhengzhou (73 mg g^-1) > Qiyang (65 mg g^-1) > Gongzhuling (55 mg g^-1). The Olsen P level increased as the total P increased, which may result in a decrease in PUE. To achieve a relatively high crop yield, PUE, and soil fertility, the optimum Olsen P range should be 13-40, 10-40, and 29-40 mg kg^-1 at Gongzhuling, Zhengzhou, and Qiyang, respectively.     

Phosphorus uptake and rhizosphere properties of intercropped and monocropped maize, faba bean, and white lupin in acidic soil

Little information is available on phosphorus (P) uptake and rhizosphere processes in maize (Zea mays L.), faba bean (Vicia faba L.), and white lupin (Lupinus albus L.) when intercropped or grown alone in acidic soil. We studied P uptake and soil pH, carboxylate concentration, and microbial community structure in the rhizosphere of maize, faba bean, and white lupin in an acidic soil with 0–250 mg P (kg⁻¹ soil) as KH₂PO₄ (KP) or FePO₄ (FeP) with species grown alone or intercropped. All plant species increased the pH compared to unplanted control, particularly faba bean. High KP supply (>100 mg P kg⁻¹) significantly increased carboxylate concentration in the rhizosphere of maize. The carboxylate composition of the rhizosphere soil of maize and white lupin was significantly affected by P form (KP or FeP), whereas, this was not the case for faba bean. In maize, the carboxylate composition of the rhizosphere soil differed significantly between intercropping and monocropping. Yield and P uptake were similar in monocropping and intercropping. Monocropped faba bean had a greater concentration of phospholipid fatty acids in the rhizosphere than that in intercropping. Intercropping changed the microbial community structure in faba bean but not in the other corps. The results show that P supply and P form, as well as intercropping can affect carboxylate concentration and microbial community composition in the rhizosphere, but that the effect is plant species-specific. In contrast to previous studies in alkaline soils, intercropping of maize with legumes did not result in increased maize growth suggesting that the legumes did not increase P availability to maize in this acidic soil.     

Variation in Yield,Phosphorus Uptake,and Physiological Efficiency of Wheat Genotypes at Adequate and Stress Phosphorus Levels in Soil

Genetic differences among crop genotypes can be exploited for identification of genotypes more suited to a low‐input agricultural system. Twenty wheat (Triticum aestivum L.) genotypes were evaluated for their differential yield response, phosphorus (P) uptake in grain and straw, and P‐use efficiency at the zero‐P control and 52 kg P ha^?1 rates. Substantial and significant differences were obvious among genotypes for both grain and straw yields at stress (8 mg P kg^?1 soil, native soil P, no P addition) and adequate (52 kg P ha^?1) P levels. Genotype 5039 produced maximum grain yield at both P levels. Relative reduction in grain yield due to P‐deficiency stress [i.e., P stress factor (PSF)] ranged between none and 32.4%, indicating differential P requirement of these genotypes. Pasban 90, Pitic 62, Rohtas 90, Punjab 85, and line 4943 did not respond to P application and exhibited high relative yield compared to those at adequate P level. FSD 83 exhibited the best response to P with maximum value for PSF (32.4%). Genotypes were distributed into nine groups on the basis of relationship between grain yield and total P uptake. Rohtas 90 and lines 4072 and 5039 exhibited high grain yield and medium P uptake (HGY‐MP). However, line 5039 with high total index score utilized less P (12.2 kg P ha^?1) than line 4072 and Rohtas 90 (13.5 and 13.6 kg P ha^?1, respectively). Moreover, this genotype also had greater P harvest index (PHI, %) and P physiological efficiency index (PPEI) at stress P level. Pasban 90, Pitic 62, and Pak 81 had the greatest total index score (21), mainly due to high total P uptake, but yielded less grain than lines 5039 and 4072 under low available P conditions. Line 6142 had minimum total index score (15) and also produced minimum grain yield. A wide range of significant differences in PPEI (211 to 365 kg grain kg^?1 P absorbed at stress and 206 to 325 kg grain kg^?1 P absorbed by aboveground plant material at adequate P) indicated differential utilization of absorbed P by these genotypes for grain production at both P levels. It is concluded from the results that wheat genotypes differed considerably in terms of their P requirements for growth and response to P application. The findings suggest that PSF, PHI, and PPEI parameters could be useful to determine P‐deficiency stress tolerance in wheat.     

RESPONSES OF COOL-SEASON GRAIN LEGUMES AND WHEAT TO SOIL-APPLIED ZINC

The yield and zinc (Zn) content response of faba bean (Vicia faba L.), chickpea (Cicer arietinum L.), lentil (Lens culinaris Medik.) and wheat (Triticum aestivum L.) to applications of Zn fertilizer was compared in a glasshouse experiment using two alkaline soils from southwestern Australia. Comparative Zn requirements were determined from yields of 46-day-old dried shoots when no Zn fertilizer was applied, the amount of Zn required to produce the same percentage of the maximum (relative) yield of dried shoots, and the Zn content of dried shoots (Zn concentration multiplied by yield of dried shoots). The concentration of Zn in youngest tissue and in dried shoots was used to determine critical concentrations for Zn in tissue. Faba bean used indigenous soil Zn more effectively than chickpea, followed by wheat and then lentil. The Zn requirement was lowest for faba bean, and increased in the order faba bean < chickpea < wheat < lentil. Zinc concentration in dried youngest tissue and in dried shoots increased with an increase in the amount of added Zn. The critical Zn concentration in the youngest tissue, associated with 90% of the relative yield, was (mg Zn kg^?1): 25 for lentil, 18 for faba bean, 17 for chickpea and 12 for wheat; corresponding values for dried whole tops (mg Zn kg^?1) were: 30 for lentil, 19 for faba bean, 17 for chickpea, and 20 for wheat. Information on comparative responses of the grain legumes to Zn additions relative to wheat, and critical tissue test values, will aid in the fertilizer management of Zn in cool-season grain legumes in the southwestern Australian farming systems.     

Quality,yield and nitrogen fixation of faba bean seeds as affected by sulphur fertilization

Abstract

Faba bean (Vicia faba L.) is an important source of plant protein for humans and animals; however, nutritional value of seeds is notoriously deficient in sulphur (S)-containing amino acids. In this article, the effect of S fertilization on faba bean's capability of N₂ fixation, grain yield and chemical characteristics in terms of protein fractions, fatty acids and minerals composition is reported. A randomized, complete block design with three replicates was used, and three S applications (0, 30 and 60 kg ha^?1, respectively) for faba bean were performed. The S fertilization was split into two applications: 50% before sowing and 50% in the beginning of March as K₂SO₄. At the same time, both the legume and oat crops were fertilized uniformly with 10 kg N ha^?1 as ¹⁵N NH₄ ¹⁵NO₃ (10% ¹⁵N atomic excess) in solution form. In a Mediterranean climate under optimal spring rainfall situations, faba bean produced high yield of grain and protein. Sulphur application resulted in an increase in overall plant yield and N₂ fixation. In addition, S fertilization enhanced the protein quality, increasing its degradable fraction. Fertilizing faba bean with 30 kg ha^?1 of S resulted in a more appropriate dose in order to obtain a quantitative and qualitative crop improvement. From our findings, it can be concluded that S fertilization to faba bean should be recommended to soils with suboptimal S levels to obtain maximum seed and protein yields.     

Current potassium‐management status and grain‐yield response of Chinese maize to potassium application

The great achievement of the development of intensive in agriculture in China can be partly attributed to substantial increases in mineral‐nutrient application. However, whereas farmers tend to apply high levels of nitrogen (N) and phosphorus (P) application of potassium (K) has been neglected. A greater understanding of the relationship between maize (Zea mays L.) grain yield and K‐application rate is thus required to provide an improved rationale for K fertilization for farmers in the various agro‐ecological regions of China. In this study, a total of 2765 farmers' survey data and 3124 on‐farm experiments across major maize agro‐ecological regions in China were collected and evaluated for farmers' K‐management status and to determine grain‐yield response to K application. Nationally, the average K‐application rate on farms was 26 kg K ha^–1 and varied from 0 to 158 kg K ha^–1, with a coefficient of variation of 107%, but the applied K‐fertilizer rates were not related to grain yield. Maize grain yields at recommended K rates increased by 14.0%, 14.7%, 19.4%, and 4.3% in Northeast China, North China Plain, Southwest China, and Northwest China, respectively, compared to zero K fertilization (K₀). Increased yield due to K fertilization (IY_max, difference between maximum yield across all treatments and K₀‐treatment yield for each experiment) averaged 1.4 t ha^–1 but varied widely in different agro‐ecological regions. Soil extractable K (NH₄OAc‐K) and intercounty variation resulted in large variation in IY_max in agro‐ecological regions, as did other factors, such as use of particular maize hybrids, soil types, or years in different regions.     

Effectiveness of native Rhizobium on nodulation and yield of faba bean (Vicia faba L.) in Eastern Ethiopia

This study was initiated to evaluate the effect of locally isolated Rhizobium on nodulation and yield of faba bean at Haramaya, Ethiopia for three consecutive years. Ten treatments comprising of eight effective isolates of rhizobia, uninoculated, and N-fertilized (20 kg N ha^?1) were laid out in a randomized complete block design with three replications. The result of the experiment indicated that all inoculation treatments increased nodule number and dry weight over the control check in all cropping seasons. The result, however, showed the non-significant effect of Rhizobium inoculation on shoot length, number of tiller per plant and 100 seed weight in all cropping season. Inoculating Haramaya University Faba Bean Rhizobium (HUFBR)-15 in 2011 and National Soil Faba Bean Rhizobium (NSFBR)-30 in 2012 and 2013 gave the highest grain yields (4330, 5267 and 4608 kg ha^?1), respectively. These records were 75%, 48%, and 5% over the uninoculated treatment of respective years. Over the season, NSCBR-30 inoculation resulted in the highest nodulation and grain yield production as compared to the other treatments. In general, isolates from central Ethiopia were better than those isolated from eastern Ethiopia and Tropical Agricultural Legume (TAL)-1035 in enhancing faba bean production at Haramaya site. Therefore, NSFBR-30 is recommended as a candidate isolate for faba bean biofertilizer production in eastern Ethiopia soils.     

Adapting and evaluating APSIM-SoilP-Wheat model for response to phosphorus under rainfed conditions of Pakistan

Phosphorus (P) treatments were used to evaluate APSIM-SoilP-Wheat model and phosphorus use efficiency (PUE) of two wheat cultivars (NARC-2009 and Chakwal-50) during 2011–2013. Overall, the Agricultural Production Systems Simulator (APSIM) model accurately simulated dry matter, grains per spike, grain yield, biomass P, and grain P for two years, for both genotypes in response to all P fertilizer treatments. NARC-2009 had 55% higher PUE compared to Chakwal-50. Information on PUE will be helpful in breeding high PUE cultivars. Modeling results showed that the production of wheat depends on growth as well as on P uptake of the plants. The close agreement between observed and simulated results confirmed the accuracy of the model which was validated with skill scores like R² and RMSE. APSIM simulation proved to be valuable tool to evaluate PUE under rainfed conditions.     

Complementary resource use in intercropped faba bean and cabbage by increased root growth and nitrogen use in organic production

Intercropping can improve yield and nitrogen use efficiency in organic vegetable production by pairing crops with complementary resource use. An intercrop field experiment was conducted to determine yield, root growth and nitrogen (N) dynamics using faba bean (Vicia faba L.) grown as a vegetable and pointed cabbage (Brassica oleracea var. capitata cv. conica). Both crops were grown in monocropping (MC) and intercropping systems (IC). Minirhizotrons were used to measure root growth. Yield of pointed cabbage per metre row was 28% higher under the IC system than under MC, whereas faba bean yield as fresh seeds did not differ. The land equivalent ratio was 1.06, showing that improved yield under IC resulted from efficient land resource use. Even though MC cabbage had the highest aboveground biomass, total N accumulation was higher under IC and MC faba bean systems. Both root frequency and intensity were greater under IC faba bean rows compared with MC faba bean because of the presence of cabbage roots in faba bean rows. Monocropped cabbage had the highest root intensity and the lowest amount of soil mineral N in the 0–1.5 m depth after harvest. Monocropped cabbage was efficient in assimilating N, whereas MC faba bean was efficient in exporting N as harvestable yield. The nitrogen use efficiency using the IC system (75%) was higher than growing faba bean (44%) and cabbage (65%) alone. Thus, faba bean as an intercrop in organic cabbage production systems improves land and N use efficiency by complementary root growth.     

Developing nitrogen management strategies under drip fertigation for wheat and maize production in the North China Plain based on a 3‐year field experiment

The intensive winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) cropping systems in the North China Plain (NCP) rely on the heavy use of mineral nitrogen (N) fertilizers. As the fertigated area of wheat and maize in the NCP has grown rapidly during recent years, developing N management strategies is required for sustainable wheat and maize production. Field experiments were conducted in Hebei Province during three consecutive growth seasons in 2012–2015 to assess the influence of different N fertigation rates on N uptake, yield, and nitrogen use efficiency [NUE: recovery efficiency (RE_N) and agronomic efficiency (AE_N)]. Five levels of N application, 0 (FN₀), 40 (FN_40%), 70 (FN_70%), 100 (FN_100%), and 130% (FN_130%) of the farmer practice rate (FP: 250 kg N ha^?1 and 205.5 kg N ha^?1 for wheat and maize, respectively), corresponding to 0, 182.2, 318.9, 455.5, and 592.2 kg N ha^?1 y^?1, respectively, were tested. Nitrogen in the form of urea was dissolved in irrigation water and split into six and four applications for wheat and maize, respectively. In addition, the treatment “drip irrigation + 100% N conventional broadcasting” (DN_100%) was also conducted. All treatments were arranged in a randomized complete block design with three replications. The results revealed the significant influence of both N fertigation rate and N application method on grain yield and NUE. Compared to DN_100%, FN_100% significantly increased the 3‐year averaged N recovery efficiency (RE_N) by 0.09 kg kg^?1 and 0.04 kg kg^?1, and the 3‐year averaged N agronomic efficiency (AE_N) by 2.43 kg kg^?1 and 1.62 kg kg^?1 for wheat and maize, respectively. Among N fertigation rates, there was no significant increase in grain yield in response to N applied at a greater rate than 70% of FP due to excess N accumulation in vegetative tissues. Compared to FN_70%, FN_100%, and FN_130%, FN_40% increased the RE_N by 0.17–0.57 kg kg^?1 and 0.03–0.34 kg kg^?1and the AE_N by 4.60–27.56 kg kg^?1 and 2.40–10.62 kg kg^?1 for wheat and maize, respectively. Based on a linear‐response relationship between the N fertigation rate and grain yield over three rotational periods it can be concluded that recommended N rates under drip fertigation with optimum split applications can be reduced to 46% (114.6 kg N ha^?1) and 58% (116.6 kg N ha^?1) of FP for wheat and maize, respectively, without negatively affecting grain yield, thereby increasing NUE.     

Effect of zinc‐biofortified seeds on grain yield of wheat,rice, and common bean grown in six countries

Seeds enriched with zinc (Zn) are ususally associated with better germination, more vigorous seedlings and higher yields. However, agronomic benefits of high‐Zn seeds were not studied under diverse agro‐climatic field conditions. This study investigated effects of low‐Zn and high‐Zn seeds (biofortified by foliar Zn fertilization of maternal plants under field conditions) of wheat (Tritcum aestivum L.), rice (Oryza sativa L.), and common bean (Phaseolus vulgaris L.) on seedling density, grain yield and grain Zn concentration in 31 field locations over two years in six countries. Experimental treatments were: (1) low‐Zn seeds and no soil Zn fertilization (control treatment), (2) low‐Zn seeds + soil Zn fertilization, and (3) Zn‐biofortified seeds and no soil Zn fertilization. The wheat experiments were established in China, India, Pakistan, and Zambia, the rice experiments in China, India and Thailand, and the common bean experiment in Brazil. When compared to the control treatment, soil Zn fertilization increased wheat grain yield in all six locations in India, two locations in Pakistan and one location in China. Zinc‐biofortified seeds also increased wheat grain yield in all four locations in Pakistan and four locations in India compared to the control treatment. Across all countries over 2 years, Zn‐biofortified wheat seeds increased plant population by 26.8% and grain yield by 5.37%. In rice, soil Zn fertilization increased paddy yield in all four locations in India and one location in Thailand. Across all countries, paddy yield increase was 8.2% by soil Zn fertilization and 5.3% by Zn‐biofortified seeds when compared to the control treatment. In common bean, soil Zn application as well as Zn‐biofortified seed increased grain yield in one location in Brazil. Effects of soil Zn fertilization and high‐Zn seed on grain Zn density were generally low. This study, at 31 field locations in six countries over two years, revealed that the seeds biofortfied with Zn enhanced crop productivity at many locations with different soil and environmental conditions. As high‐Zn grains are a by‐product of Zn biofortification, use of Zn‐enriched grains as seed in the next cropping season can contribute to enhance crop productivity in a cost‐effective manner.     

Root turnover of faba beans (Vicia faba L.) and its interaction with P and K supply

An increased root turnover can be a mechanism of improved nutrient‐uptake efficiency. The objectives of this study were to investigate P and K efficiency of faba beans (Vicia faba L.), to determine their root growth and root turnover, and to assess the relevance of root turnover on P and K uptake at limited supply. Faba beans were grown as part of a long‐term fertilization experiment on fertilized plots (control) and plots that had not received any P or K fertilizer for 16 years (P0, K0). Although the unfertilized soils were low and very low in their P‐ and K‐supply level, respectively, no differences in shoot‐dry‐matter production occurred compared to the control. However, relative K concentration in dry matter of the K0 plants (control plants = 100) decreased during the experiment and was only 60% of the control at the final harvest. This indicated a high K‐utilization efficiency of faba bean. Relative phosphorus concentration increased in the P0 treatment and was not different from the control at the last harvest, indicating an improvement in P‐uptake efficiency with time. The size of the standing root system determined by sequential auger sampling (net development) was not influenced by P and K supply. Total root production as measured by the ingrowth‐core method was about 6 times higher than the average size of the standing root system and even increased under low‐K conditions. This indicated a fast root turnover. Modeling soil nutrient transport and uptake revealed that calculated uptake of the control was up to 48% higher when root turnover was taken into account, compared to calculations based on the net development of the root systems. This is due to a better soil exploitation. Under K shortage, root turnover resulted in a 117% higher calculated uptake, which was close to measured K uptake. Root turnover was also of benefit for P uptake, but calculated P uptake was significantly less than measured, indicating that root turnover was of little importance for P uptake of faba beans.     

Biological nitrogen fixation in faba bean (Vicia faba L.) in the Ethiopian highlands as affected by P fertilization and inoculation

 N₂ fixation by leguminous crops is a relatively low-cost alternative to N fertilizer for small-holder farmers in developing countries. N₂ fixation in faba bean (Vicia faba L.) as affected by P fertilization (0 and 20 kg P ha^–1) and inoculation (uninoculated and inoculated) with Rhizobium leguminosarium biovar viciae (strain S-18) was studied using the ¹⁵N isotope dilution method in the southeastern Ethiopian highlands at three sites differing in soil conditions and length of growing period. Nodulation at the late flowering stage was significantly influenced by P and inoculation only at the location exhibiting the lowest soil P and pH levels. The percentage of N derived from the atmosphere ranged from 66 to 74%, 58 to 74% and 62 to 73% with a corresponding total amount of N₂ fixed ranging from 169 to 210 kg N ha^–1, 139 to 184 kg N ha^–1 and 147 to 174 kg N ha^–1 at Bekoji, Kulumsa and Asasa, respectively. The total N₂ fixed was not significantly affected by P fertilizer or inoculation across all locations, and there was no interaction between the factors. However, at all three locations, N₂ fixation was highly positively correlated with the dry matter production and total N yield of faba bean. Soil N balances after faba bean were positive (12–58 kg N ha^–1) relative to the highly negative N balances (–9–44 kg N ha^–1) following wheat (Triticum aestivum L.), highlighting the importance of rotation with faba bean in the cereal-based cropping systems of Ethiopia. Received: 13 January 2000     

Efficiency of Magnesium Use by Common Bean Varieties Regarding Yield,Physiological Components,and Nutritional Status of Plants

The magnesium (Mg) use efficiency in the selection of common bean (Phaseolus vulgaris L.) varieties may contribute to increased nutritional status and grain yield. Therefore, the present study aimed to assess common bean varieties following the application of Mg regarding productivity (yield), soil fertility, physiological components, and nutritional status. The experiment was conducted in a completely randomized design in a 5 × 2 factorial scheme with three replicates. Five common bean varieties [BRS Estilo, IPR Tangará, IPR Campos Gerais (CG), IAPAR 81, and BRS Ametista] supplemented with two Mg concentrations [low (0 mg kg^?1) and high (100 mg kg^?1)] using magnesium chloride (MgCl₂) as a source in an Ustoxix Quatzipsamment were assessed. The yield of shoot dry weight (SDW) and grains varied significantly between varieties and Mg rates. The high Mg concentration has negatively affected the yield of SDW and grains of variety IPR Tangará, and the opposite was observed for the other varieties. The physiological components associated with photosynthesis are directly related to the yield of SDW and grains. The concentrations of phosphorus (P), calcium (Ca), sulfur (S), and boron (B) in leaves and of S, B, iron (Fe), and manganese (Mn) in grains differed among the varieties and interactions of rates and varieties for B, indicating the presence of genetic factors in nutrient uptake.     

Yield and Yield Components and Phosphorus Use Efficiency of Lowland Rice Genotypes

Phosphorus deficiency is main constraints for lowland rice production in various rice producing regions of the world. A greenhouse experiment was conducted using lowland (Inceptisol) soil with the objective to determine response of seven lowland rice (Oryza sativa L.) genotypes to phosphorus fertilization and to evaluate their phosphorus (P) use efficiency. Phosphorus treatments included control (0 mg P kg^?1) and 200 mg P kg^?1 of soil. Plant height and shoot dry weight were significantly (P < 0.001) influenced by P treatments. Phosphorus X genotypes interaction was significant for shoot dry weight, indicating different response of genotypes under two P levels. At low P level, none of the genotypes produced grain yield, indicating original P level in the soil was too low for lowland rice yield. However, genotypes differed significantly in grain yield at high P level. Panicle number, panicle length, and thousand grains weight had a significant quadratic association with grain yield. However, spikelet sterility had a significant linear negative association with grain yield. The P use efficiency expressed as agronomic efficiency (AE), physiological efficiency (PE), agro-physiological efficiency (AP), apparent recovery efficiency (ARE), and utilization (UE) were significantly different among genotypes. These efficiencies were having significantly positive association with grain yield, with exception to ARE, indicating improving grain yield with improved P use efficiencies in rice.     

Nodulation and root growth increase in lower soil layers of water‐limited faba bean intercropped with wheat

Below‐ground niche complementarity in legume–cereal intercrops may improve resource use efficiency and root adaptability to environmental constraints. However, the effect of water limitation on legume rooting and nodulation patterns in intercropping is poorly understood. To advance our knowledge of mechanisms involved in water‐limitation response, faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) were grown as mono‐ and intercrops in soil‐filled plexiglass rhizoboxes under water sufficiency (80% of water‐holding capacity) and water limitation (30% of water‐holding capacity). We examined whether intercropping facilitates below‐ground niche complementarity under water limitation via interspecific root stratification coupled with modified nodulation patterns. While no significant treatment effects were measured in intercropped wheat growth parameters, water limitation induced a decrease in shoot and root biomass of monocropped wheat. Likewise, shoot biomass and height, and root length of monocropped faba bean significantly decreased under water limitation. Conversely, water limitation stimulated root biomass of intercropped faba bean in the lower soil layer (15–30 cm soil depth). Similarly, total nodule number of faba bean roots as well as nodule number in the lower soil layer increased under intercropping regardless of water availability. Under water limitation, intercropping also led to a significant increased nodule biomass (48%) in the lower soil layer as compared to monocropping. The enhanced nodulation in the lower soil layer and the associated increase in root and shoot growth provides evidence for a shift in niche occupancy when intercropped with wheat, which improves water‐limited faba bean performance.