Absence Of Nitrogen Fertilization Research Articles

Effects of alternative fertilization on common bean crops regarding productivity and nutritional levels

Considering the need for more information about productivity increases and nutritional improvement of soils, the present study evaluated the effects of alternative fertilization on grain yield and nutritional levels of bean crops. It was a randomized block study with four treatments and five replicates. The treatments were the absence of nitrogen fertilization, fertilizer use, chicken litter, and cattle manure. Organic fertilization provided lower variations in soil water availability during flowering and grain filling and increased nutrient concentrations, especially phosphorus and potassium. Chicken litter promoted the highest means for the number of legumes, the number of legumes on branches, the number of six-grain legumes, the mass of a thousand grains, grain mass per plant, and the normalized green-red difference index. However, the two organic fertilizers had significantly higher differences from chemical and no fertilization, showing that organic fertilizer applications must occur when nutrient availability coincides with the phenological stages essential for producing these fertilizers. High yields combined with favorable rainfall conditions occurred during crop development, as high soil moisture allowed faster mineralization of essential organic fertilizer nutrients, directly affecting yield. Pearson’s linear correlation allowed a better understanding of the participation of each plant trait in productivity, and the highest grain yield occurred with organic fertilization.

Impact of Azospirillum sp. B510 on the Rhizosphere Microbiome of Rice under Field Conditions

There has been increasing attention toward the influence of biofertilizers on the composition of microbial communities associated with crop plants. We investigated the impact of Azospirillum sp. B510, a bacterial strain with nitrogen-fixing ability, on the structure of bacterial and fungal communities within rice plant rhizospheres by amplicon sequencing at two sampling stages (the vegetative and harvest stages of rice). Principal coordinate analysis (PCoA) demonstrated a significant community shift in the bacterial microbiome when the plants were inoculated with B510 at the vegetative stage, which was very similar to the effect of chemical N-fertilizer application. This result suggested that the inoculation with B510 strongly influenced nitrogen uptake by the host plants under low nitrogen conditions. Least discriminant analysis (LDA) showed that the B510 inoculation significantly increased the N2-fixing Clostridium, Aeromonas and Bacillus populations. In contrast, there was no apparent influence of B510 on the fungal community structure. The putative functional properties of bacteria were identified through PICRUSt2, and this hinted that amino acid, sugar and vitamin production might be related to B510 inoculation. Our results indicate that B510 inoculation influenced the bacterial community structure by recruiting other N2-fixing bacteria in the absence of nitrogen fertilizer.

Seed vigor in performance of wheat plants: evidence of interaction with nitrogen

Abstract: The use of high-quality seeds is an important factor in the crop production system. Its benefits to the performance of plants and possible interactions with other factors - such as nitrogen fertilization - could be better understood from a multivariate analysis perspective. With this approach, the objective of this work was to evaluate the impacts of wheat seed vigor and possible interactions with nitrogen fertilization on the performance of wheat plants. The data analyzed were obtained from the average results gathered through three experimental environments, located in the department of Alto Paraná, Paraguay. High-vigor seeds with provided a better plant stand and also a greater growth in the formed tillers stage. This category also provided plants with higher performance - a condition found for dry matter weight - in the booting, flowering and milk seed stages, in the presence and absence of nitrogen fertilization. The multivariate analysis showed that plants originating from high-vigor seeds that had not been fertilized with N showed a similar performance to that of low-vigor plants, but fertilized with N. High-vigor wheat seeds provide plants with superior performance.

Interaction between nitrogen, soil water condition and herbicides in Urochloa plantaginea control in irrigated rice crop

ABSTRACT The present study sought to verify the existence of interactions between the soil water conditions, nitrogen and herbicides commonly used to control alexandergrass in irrigated rice crop. The experimental design was completely randomized, arranged in a 2 x 3 x 4 factorial scheme, corresponding to two soil water conditions (5 cm water depth and 100% soil water holding capacity [WHC]), three nitrogen doses (0, 80 and 160 kg of N ha-1) and four doses of herbicides (0, 0.5, 1 and 2 times the registration dose). The herbicides evaluated were cyhalofop-butyl, imazapyr + imazapic and imazethapyr. The treatments were repeated four times. Phytotoxicity and dry mass were evaluated 28 days after application. For cyhalofop-butyl and imazapyr + imazapic, the phytotoxicity at 100% WHC and 5 cm water depth conditions was higher in treatments with nitrogen fertilization. However, for imazethapyr under the 100% WHC condition of soil increased phytotoxicity in the absence of nitrogen fertilization. For the flooded condition, from the dose of 35 g of a.i. ha-1, the result in the control for the herbicide imazethapyr was optimized under the conditions of fertilization with 80 and 160 kg of N ha-1. Cyhalofop-butyl and imazapyr + imazapic undergo synergistic interaction with nitrogen fertilization and water status in the control efficiency, yet with imazethapyr, the synergistic interaction only occurs under 100% of soil WHC.

Effects of Nitrogen Fertilization on Mycorrhizal Infection, Nodulation and Growth of Phaseolus vulgaris L.

Summary The common bean (Phaseolus vulgaris L.) has been the subject of a number of studies and has been described by many authors as a legume with low nitrogen fixing potential compared to other legume species. The first objective of this study is to assess the development and growth of P. vulgaris L. var. Djedida and its yield at different developmental stages (vegetative, flowering and fruiting), in the presence and absence of nitrogen fertilizer (Urea 46) in an arid climate and in a soil containing high level of CaCO3 and assimilable phosphorus. The second objective is to carry out a survey on nodulation, number of spores and mycorrhizal infection under these conditions. The results showed that the nitrogen fertilizer amendment is mainly significant (p< 0.0001) for various morphological parameters. Indeed, great improvement was observed on the majority of the morphological parameters with considerable percentages. However, no significant effect was reported for the roots length. In addition, a negligible number of nodules were obtained in the plot without fertilization and no significant effect on the number of spores was recorded. Furthermore, the effect of fertilization on the arbuscular intensity (a%, A%) and on mycorrhizal colonization (M%, m%) of the roots was found to be significant. The soil in the arid region of Biskra showed significant mycorrhizogenic potential, although the conditions in this region were not very favorable for their development, which could constitute an effective biological resource to improve the tolerance of host plants to biotic and abiotic constraints.

Ecosystem service provision of grain legume and cereal intercropping in Africa

Achieving food security is challenging in Africa, a continent beset by low crop yield and soil quality, climate adversities, pests, weed infestations, and crop disease outbreaks. In this context, it is important to re-visit the resource-use efficiency and ecosystem service values of intercropping of grain legumes and cereals, a practice that has long been used by small-scale producers to mitigate the risk of crop failure and to safeguard household food availability. Despite its historical use, there are significant knowledge gaps regarding multiple aspects of intercropping, including examination of the different crop combinations on ecosystem services from agriculture. Using meta-analysis approach of land equivalent ratio (LER), a widely-accepted index to assess the efficiency of intercropping production systems, we found that intercropping of cereals with legumes resulted in an elevated LER (i.e., 1.31), regardless of species combination. A significantly greater LER than the overall LER (P < .05) was observed with the combination of maize-pigeon pea (LER = 1.57) and maize-groundnut (LER = 1.52). Increasing LER with intercropping was constant across rainfall variability, as well as in the absence of nitrogen fertilizer, which are the hallmark properties of intercropping in resource-deprived Africa. Intercropping could also reduce soil erosion, pest/weed incidence, and increase carbon sequestration by about ~46%, ~20–30%, and ~15%, respectively, compared to its sole crop control. In this comprehensive quantitative assessment of intercropping benefits across the African continent, we highlighted the provision of different ecosystem services from agroecosystems, a crucial foundation to achieving sustainable agricultural production.

Tillering dynamics of Alexandergrass pasture under nitrogen fertilization

ABSTRACT This study was carried out to evaluate the effect of nitrogen fertilization on tillering dynamics of Alexandergrass (Urochloa plantaginea (Link) Hitch) grazed by beef heifers in a rotational stocking grazing method. The experiment was conducted in a completely randomized design following a repeated measure arrangement, three levels of nitrogen (Zero, 150 and 300kg ha-1) and two area repetition. The classification of tillers into categories (basal and axillary) showed a greater number of basal tillers, due to their higher appearance rate, in the absence of nitrogen fertilization. Nitrogen fertilization promoted higher axillary tiller density. The use of nitrogen promotes the renewal of axillary tillers of Alexandergrass, without compromising the stability of the tiller population.

Biometric and Bromatological Characteristics of Brachiaria Inoculated With Azospirillum brasilense Associated With Nitrogen Fertilization

The objective of this study was to evaluate the biometric and bromatological characteristics of Urochloa ruziziensis in due to inoculation times with Azospirillum brasilense in the presence or absence of nitrogen fertilization. To do so it was used a randomized blocks design, with factorial scheme 4 &amp;times; 2, where the first factor consisted the inoculation periods: control; A. brasilense in the seed; A. brasilense at tillering (aerial) and A. brasilense seed + foliar. The second factor constituted in the presence or absence of nitrogen (1000 mg dm&amp;sup3;). Evaluations were made in the first, second and third cut, being evaluated the plant height, number of tillers per plant, leaves dry mass, culm+sheath dry mass; crude protein content, neutral detergent fiber and acid detergent fiber. The use of nitrogen fertilization increased the productive and bromatological parameters in the crop of U. ruziziensis, however, the use of A. brasilense increased only the height of plants, not influencing the other productive characteristics and the bromatological parameters. It is concluded that the use of A. brasilense, regardless the period it was made, presents inconclusive results for biometric and bromatological characteristics of plants of Urochloa ruziziensis in need of further studies, on the other hand, the nitrogen fertilization brings positive effects over the evaluated parameters on U. ruziziensis.

Nitrogen Fertilization and Inoculation of Seeds with Rhizobium tropici on the Agronomic Performance of Common Beans

Aims: This study aimed to evaluate the influence of nitrogen fertilization and inoculation of seeds with Rhizobium tropici on the agronomic performance of common bean (Phaseolus vulgaris L.).&#x0D; Study Design: The experimental design consisted of a randomized block in a 4x2 factorial layout, with 4 replicates, the first factor referring to inoculant doses (0, 50, 100 and 200 mL for each 25 kg of seed), while the second refers to nitrogen fertilization (0 and 40 kg ha of N).&#x0D; Place and Duration of Study: The study was conducted to the field in a no-till system area, in the southwestern region of Paraná, Brazil. The soil is classified as a Purple Latosol, with a clayey texture.&#x0D; Methodology: The adopted spacing was 0.45 m between rows, and the seeding density used was 12 seeds per furrow meter. The inoculants NITRO 1000 Rhizobium tropici SEMIA 4077 and SEMIA 4088 were applied, varied according to the treatments. The cultivar used was IPR – Tangará.&#x0D; Results: As for grain yield, it was observed that nitrogen fertilization did not contribute to the increase in grain yield, and higher productivity was obtained in the absence of N. This was probably due to the high content of organic matter present in the soil.&#x0D; Conclusion: Nitrogen fertilization at sowing and seed inoculation with Rhizobium tropici did not influence the plant population and the 1000-grain mass. In the absence of nitrogen fertilization at sowing, pods with a longer length and higher grain yield were obtained. Inoculation of the seeds with Rhizobium tropici exerts a positive influence on plant height, number of nodes of the main stem, number of pods per plant, and number of beans per pod, the dose recommended by the manufacturer (100 mL) being efficient, with the possibility of applying a dose of 50 mL, to satisfactory results.

&lt;b&gt;Technical and economic viability and nutritional quality of mombasa guinea grass silage production

The objective of this study was to evaluate the viability of pasture with high production capacity and the potential for production of silage using different sources and doses of nitrogen (N) by quantifying the productivity of dry matter (DM), some qualitative characteristics, the total cost of production (TC) and total operating cost (TOC) of silage production. The experimental design was randomized block in a factorial scheme with four replications including two sources of nitrogen (urea and ammonium nitrate) and five N doses (0, 50, 100, 150, and 200 kg ha-1 by cutting). The increase in N provided greater DM and crude protein content and reduced the fiber content in neutral detergent. The source of N did not affect the chemical composition, and therefore, it is recommended to use urea due to the ease of acquisition and higher economic return. The production of Mombasa silage can be economically viable due to high DM and crude protein content combined with low production costs. The smallest TC and TOC were obtained in the absence of nitrogen fertilization; however, the proper management of N ensures high productivity in cattle feed with higher total profit when using 100 kg ha-1 N by cutting with ammonium nitrate. 

Solute and sediment export from Amazon forest and soybean headwater streams.

Intensive cropland agriculture commonly increases streamwater solute concentrations and export from small watersheds. In recent decades, the lowland tropics have become the world's largest and most important region of cropland expansion. Although the effects of intensive cropland agriculture on streamwater chemistry and watershed export have been widely studied in temperate regions, their effects in tropical regions are poorly understood. We sampled seven headwater streams draining watersheds in forest (n=3) or soybeans (n=4) to examine the effects of soybean cropping on stream solute concentrations and watershed export in a region of rapid soybean expansion in the Brazilian state of Mato Grosso. We measured stream flows and concentrations of NO3- , PO43- , SO42- , Cl- , NH4+ , Ca2+ , Mg2+ , Na+ , K+ , Al3+ , Fe3+ , and dissolved organic carbon (DOC) biweekly to monthly to determine solute export. We also measured stormflows and stormflow solute concentrations in a subset of watersheds (two forest, two soybean) during two/three storms, and solutes and δ18 O in groundwater, rainwater, and throughfall to characterize watershed flowpaths. Concentrations of all solutes except K+ varied seasonally in streamwater, but only Fe3+ concentrations differed between land uses. The highest streamwater and rainwater solute concentrations occurred during the peak season of wildfires in Mato Grosso, suggesting that regional changes in atmospheric composition and deposition influence seasonal stream solute concentrations. Despite no concentration differences between forest and soybean land uses, annual export of NH4+ , PO43- , Ca2+ , Fe3+ , Na+ , SO42- , DOC, and TSS were significantly higher from soybean than forest watersheds (5.6-fold mean increase). This increase largely reflected a 4.3-fold increase in water export from soybean watersheds. Despite this increase, total solute export per unit watershed area (i.e., yield) remained low for all watersheds (<1kg NO3- N·ha-1 ·yr-1 , <2.1kg NH4+ -N·ha-1 ·yr-1 , <0.2kg PO43- -P·ha-1 ·yr-1 , <1.5kg Ca2+ ·ha-1 ·yr-1 ). Responses of both streamflows and solute concentrations to crop agriculture appear to be controlled by high soil hydraulic conductivity, groundwater-dominated hydrologic flowpaths on deep soils, and the absence of nitrogen fertilization. To date, these factors have buffered streams from the large increases in solute concentrations that often accompany intensive croplands in other locations.

Bioenergy cropping systems that incorporate native grasses stimulate growth of plant-associated soil microbes in the absence of nitrogen fertilization

The choice of crops and their management can strongly influence soil microbial communities and their processes. We used lipid biomarker profiling to characterize how soil microbial composition of five potential bioenergy cropping systems diverged from a common baseline five years after they were established. The cropping systems we studied included an annual system (continuous no-till corn) and four perennial crops (switchgrass, miscanthus, hybrid poplar, and restored prairie). Partial- and no-stover removal were compared for the corn system, while N-additions were compared to unfertilized plots for the perennial cropping systems. Arbuscular mycorrhizal fungi (AMF) and Gram-negative biomass was higher in unfertilized perennial grass systems, especially in switchgrass and prairie. Gram-positive bacterial biomass decreased in all systems relative to baseline values in surface soils (0–10cm), but not subsurface soils (10–25cm). Overall microbial composition was similar between the two soil depths. Our findings demonstrate the capacity of unfertilized perennial cropping systems to recreate microbial composition found in undisturbed soil environments and indicate how strongly agroecosystem management decisions such as N addition and plant community composition can influence soil microbial assemblages.

Inoculación con hongos micorrízicos y fertilización con urea de plantas de Fraxinus uhdei en acrisoles provenientes de sitios degradados

En suelos severamente degradados el establecimiento de plantas se dificulta por la ausencia de estructura, de microorganismos del suelo y en muchos casos por las bajas concentraciones de macronutrientes. En estas condiciones, el uso de interacciones con hongos micorrízicos, podría ser una estrategia efectiva para la revegetación y la restauración ecológica. Se realizó un experimento con sustrato obtenido de un sitio severamente erosionado (acrisoles con presencia de cárcavas) en un sistema de mesocosmos, con el objetivo de evaluar el desempeño de Fraxinus uhdei (Wenz.) Lingelsh (fresno) inoculado con los hongos micorrízicos Pisolithus tinctorius y Rhizophagus intraradices , solos o en interacción y en presencia/ausencia de fertilización nitrogenada. Se evaluó la altura, la cobertura de la copa, el diámetro a la altura de la base del tallo y el número de hojas al finalizar el experimento y se cosechó la biomasa. Se prepararon muestras para verificar la micorrización. Los resultados indicaron que la fertilización no tuvo efecto significativo sobre el desarrollo de las plantas pero, afectó negativamente la supervivencia (con urea 67 %, sin urea 90 %). Los mayores valores para las variables de crecimiento y la biomasa aérea siempre correspondieron a las plantas con inoculación dual, y los menores para las plantas control o las inoculadas con P. tinctorius (altura 23.3 cm contra 15.8 cm para P. tinctorius , diámetro a la altura de la base 0.74 cm contra 0.5 para P. tinctorius , el peso seco de las partes aéreas 2.0 g contra 1.0 g del control). Los resultados sugieren que en suelos que presentan condiciones severas de degradación la co-inoculación de plantas adaptadas a condiciones adversas puede ser una estrategia eficiente de revegetación.

Implications of selection in common bean lines in contrasting environments concerning nitrogen levels

Grain productivities of 100 bean lines were evaluated in the presence and absence of nitrogen fertilizer in order to identify those with high nitrogen use efficiency (NUE) and to determine the correlated response observed in a stressed environment following selection in a non-stressed environment. The genetic and phenotypic characteristics of the lines, as wellas the response index to applied nitrogen, were determined. The average grain productivities at both locations were 39.5% higher in the presence of nitrogen fertilizer, with 8.3 kg of grain being produced per kg of nitrogen applied. NUE varied greatly between lines. Lines BP-16, CVII-85-11, BP-24, Ouro Negro and MA-IV-15-203 were the most efficient and responsive. The results showed that it is possible to select bean lines in stressed and non-stressed environments. It was inferred that common bean lines for environments with low nitrogenav ailability should preferably be selected under nitrogen stress.

Intensidade de pastejo e adubação nitrogenada na massa seca de aveia e produtividade do milho na integração lavoura-pecuária

This study aimed to evaluate the impact of different grazing intensities and nitrogen fertilization applied on oats and its effect upon maize cultivated in succession in a no tillage system. The experiment was carried out at Abelardo Luz municipality during the winter and summer seasons of 2004/2005. The experimental design was a completely randomized block in a split-plot arrangement with four replicates. Treatments were five different grazing intensities, represented by utilization periods in an oat culture grazed for 0, 3, 6, 9 and 12 weeks, and at sub-plot level nitrogen doses were applied at 0 and 150 kg/ ha. The availability and residual dry matter of oat was evaluated each three weeks after the beginning of grazing until the drying of the pasture. Was also evaluated the yield of maize after oat under different intensities of grazing and nitrogen fertilization. Results indicated the existence of interaction between grazing and winter nitrogen fertilization, which affected maize nutrition and yield. Moreover, the oat residual dry matter availability was positively influenced by applied nitrogen. The nitrogen in the pasture, besides favoring the production of residual dry matter of oats, determines the greatest potential productivity of corn in sequence. In the absence of nitrogen fertilization on winter pastures, the grazing intensity should be reduced so as not to affect the productivity of maize.

Effect of continuous olive mill wastewater applications, in the presence and absence of nitrogen fertilization, on the structure of rhizosphere-soil fungal communities

Olive mill wastewater (OMW) is rich in potentially toxic organics precluding its disposal into water receptors. However, land application of diluted OMW may result in safe disposal and fertilization. In order to investigate the effects of OMW on the structure of soil fungal groups, OMW was applied daily to pepper plants growing in a loamy sand and a sandy loam at two doses for a period of 3 months (total OMW equivalents 900 and 1800 m(3) ha(-1)). Nitrogen (N) fertilization alleviated N scarcity and considerably enhanced plant biomass production; however, when applied in combination with the high OMW dose, it induced plant stress. OMW applications resulted in marked changes in the denaturing gradient gel electrophoresis patterns of soil basidiomycete communities, while concurrent N fertilization reduced these effects. In contrast, the ascomycete communities required N fertilization to respond to OMW addition. Cloning libraries for the basidiomycete communities showed that Cryptococcus yeasts and Ceratobasidium spp. dominated in the samples treated with OMW. In contrast, certain plant pathogenic basidiomycetes such as Thanatephorus cucumeris and Athelia rolfsii were suppressed. The observed changes may be reasonably explained by the capacity of OMW to enrich soils in organic substrates, to induce N immobilization and to directly introduce OMW-derived basidiomycetous yeasts.

Repeated application of diluted olive mill wastewater induces changes in the structure of the soil microbial community

Repeated application of diluted olive mill wastewater (OMW) is a common disposal method which allows the application of large amounts of OMW and improves the organic matter and nutrient status of Mediterranean soils. However, there is lack of information regarding the effects of this practice on the soil microbial community. A study was carried out to investigate these effects on the structure of the bacterial and fungal community of a loamy sand (LS) and a sandy loam (SL) soil, using denaturating gradient gel electrophoresis (DGGE) fingerprinting. OMW was daily applied as aqueous solutions of 0, 2 and 4%, in the presence or absence of nitrogen fertilization, for a three-month period. Multivariate analysis of the DGGE profiles showed that OMW applications resulted in marked changes in the fungal community in both soils, while nitrogen fertilization diminished these effects. Small effects were evident for the bacteria only in the LS soil and this was attributed to the higher availability of OMW-derived phenolics in this soil which resulted in a direct impact on bacteria. Nitrogen fertilization alleviated the effects of OMW on the bacterial community. We suggest that the impact of OMW on the structure of the soil microbial communities was mostly a result of its indirect effect on the soil nutritional status, which becomes enriched in organic substrates and poor in available nitrogen.

Culturas antecessoras, doses e fontes de nitrogênio nos componentes de produção do milho

Antecedent crops, doses and sources of nitrogen on yield compounds of corn. Some plants for mulching have the capacity to increase the availability of nutrients in the soil – nitrogen in particular – for crop succession, thus producing positive effects on the interaction between mineral fertilizer and green manure. As a result, there is a greater possibility to obtain higher incomes than by using each one separately. The objective of this study was to evaluate the effect of antecedent crops, doses and sources of nitrogen on yield compounds and foliar nitrogen content of corn by means of no-tillage system. The experimental design was in randomized blocks with treatments arranged in sub-subdivided plots. These were constituted by crops preceding corn: black oat, wheat, pasture turnip, hairy vetch and one rest treatment during winter. Subplots were established by four doses of nitrogen (0; 50; 100 and 200 kg ha-1 of N), which were applied as cover. Sub-subplots were represented by two sources of nitrogen (ammonia sulfate and urea). Results showed that antecedent crops had some influence upon yield, mass of 1000 grains and foliar nitrogen content of corn. The highest yield of corn was obtained after the winter rest, the pasture turnip and also in the absence of nitrogen fertilization as cover. The maximum yield of corn was obtained when sowing was done after wheat and black oat, in nitrogen doses of 140 and 137 kg ha-1, respectively. The nitrogen sources utilized had some influence only upon the index of harvest, the number of grains per ear and the foliar nitrogen content.

Early remobilization: A possible source of error in the ureide assay method for N2fixation measurement by early maturing soybean

Abstract The ureide assay method has been found to be suitable for soybean (Glycine max) to assess nitrogen ixation in a wide range of genotypes and Bradyrhizobium strains. The relationships between the relative abundance of ureide-N in xylem-sap and the proportion of plant N derived from nitrogen fixation were studied for early maturing soybeans grown under greenhouse and field conditions. Plants grown under greenhouse conditions were either supplemented with N-free nutrients or supplied with different levels of 15N-nitrate. In the field, soybeans were grown with or without inoculation, in the presence or absence of nitrogen fertilizer. Treatments were applied in order to obtain a wide range of nitrogen nutrition levels. The effect of the source and level of nitrogen nutrition on growth and nitrogen accumulation in plants, proportion of fixed nitrogen in the xylem-sap and in the shoots, and the proportions of N-compounds in the xylem-sap was determined. The greenhouse study demonstrated that the relative abundance of ureide-N was closely correlated with the proportion of fixed nitrogen measured in the xylem-sap from V2V3 until R7 stages. However, in both greenhouse and field experiments a positive correlation between the relative abundance of ureide-N in the xylem-sap and fixed nitrogen measured in the shoots was only observed until the beginning of seed filling. Since the disappearance of the relationship between relative ureides and nitrogen fixation corresponded to the beginning of the filling of the grain, and to the onset of remobilization in this early maturity genotype, it is suggested that interferences from ureides synthesized from breakdown products during senescence or released from storage pools may explain the lack of correlations later in the growth cycle. Further investigations on the origin of measured ureides at different development stages should therefore be carried out.

Fibrous root growth and water use of sugar beet

SUMMARYDevelopment of the fibrous root system of sugar beet was studied by washing soil samples taken from field experiments through the growing season. At the beginning of June the root system was still poorly developed but during June there was rapid proliferation. In the top 70 cm there was only little further increase in root density after the end of June. Below 70 cm root density increased up to the end of August. Throughout the season fibrous root density decreased with depth. Despite the origin of the lateral roots from two grooves on the storage root, fibrous root distributions at each depth around individual plants were essentially uniform from mid-June onwards. In the absence of nitrogen fertilizer, fibrous root development exceeded that of a crop given fertilizer, particularly at depths greater than 50 cm early in the season. The maximum value of root density was 2·8 cm/cm3 soil recorded in the top 10 cm in mid-September. Compared with published data for other crops, the sugar-beet root system was sparser than that of winter wheat or maize but denser than that of a soya bean or cassava.Soil water content was measured with a neutron probe. Inflows to roots were calculated from soil water content changes in different soil layers. In the top 30 cm, inflows ranged up to 10·8 μl water/cm root.day and were up to five times higher than published inflows for winter wheat. At 30–100 cm sugar beet and winter wheat inflows were generally similar. The 0–30 and 30–120 cm layers contributed about 80 and 20% respectively of the total water use by sugar beet while no uptake was recorded below 110 cm. Previous studies have shown that sugar beet often takes up water from soil deeper than 110 cm, although it is not unknown for the depth of water removal to be restricted.