Total Nitrogen Uptake Research Articles

Nitrogen Uptake Rates during Spring in the NE Arabian Sea

We present new data on N uptake rates and f-ratios in the north-eastern (NE) Arabian Sea, where significant amounts of Trichodesmium were present in spring, 2006. The measured total nitrogen uptake rates ranged from 0.34 to 1.58 mmol N . fixation associated with Trichodesmium varied from 0.002 to 0.54 mmol N estimated from the abundance of Trichodesmium and specific fixation rates of 1.5 pmol N trichome. Inclusion of fixation rates significantly changes f-ratios particularly in the coastal stations. Nitrogen isotopic data of surface suspended particles suggest that recently fixed nitrogen contributes as high as ~79% of the nitrogen in surface suspended particles. In addition, water column gained ~30 mmol N in the form of nitrate, likely due to nitrification of ammonium released by Trichodesmium. For better estimations, direct measurement of fixation is recommended.

Nitrogen efficiency of wheat: Genotypic and environmental variation and prospects for improvement

Winter wheat ( Triticum aestivum L.) was grown for 4 years in multi-factorial field trials at Rothamsted, southern England. Thirty nine elite commercial cultivars (primarily short-straw) were grown including those released in the UK over a 25-year period, a selection of continental varieties, and three older, tall varieties. Varieties spanned the quality spectrum from ‘bread’ to ‘feed’. The crops were given ammonium nitrate at five rates in the range 0–350 kg-N/ha as a 3-way split. The aim was to quantify the genotypic variation in total nitrogen uptake by grain and straw (total-Nup), and in nitrogen utilization efficiency for grain yield (grain yield per unit of N taken up) (grain-NutE). Depending on treatment, grain yield ranged from 2.1 to 11.8 t/ha (85% DM), grain %N from 1.1% to 2.8% (in DM), total-Nup from 31 to 264 kg-N/ha, and grain-NutE from 27 to 77 kg-DM/kg-N. There were significant varietal differences in total N-uptake and grain-NutE both between ‘tall’ and ‘short’ varieties and within ‘short’ varieties. The best short varieties took up 31–38 kg/ha more N than the worst, and grain-NutE was 24–42% better, depending on N-rate. Up to 77% of the variation in grain-NutE was accounted for by yield. All interactions between the factors ‘Variety’, ‘Year’, and ‘N-rate’ were highly significant, but only ‘Year × N-rate’ made an important contribution to the variation. There was a near-functional inverse relationship between grain-NutE and grain %N; high-quality wheat (high grain %N) can be expected to have a low grain-NutE. The four key variables determining N-efficiency in a wheat crop – grain yield, grain %N, total N-uptake and nitrogen harvest index (NHI) – are ultimately constrained by the law of conservation of matter. Improving grain-NutE for fixed total-Nup and NHI can only be achieved at the expense of grain %N. To improve grain-NutE and maintain grain %N requires a simultaneous increase in NHI and grain starch yield which may be difficult to achieve in practice. The law of conservation of matter ultimately sets a limit on the physiological and agronomic processes that determine crop N requirements. A high yield of high-quality grain (high grain %N) requires a high input and uptake of nitrogen.

Root Exudates and Nitrogen Uptake of Wheat in Wheat/Maize/Soybean Relay Cropping System

Root exudates play a role in adjusting physical and chemical characteristics of soil, improving soil fertility, and facilitating nutrient uptake. Thus, they are used to explaining the mechanism of high nutrient utilization efficiency for plants. In the relay cropping system of wheat/maize/soybean, nitrogen use efficiency appears higher than that in the cropping system of wheat/maize/sweet potato. For explaining the relationship between the high use efficiency of nitrogen and the effects of rhizosphere microenvironment in the wheat/maize/soybean cropping system, the characteristics of wheat root exudates as well as its effects on wheat roots, wheat rhizosphere soil, and nitrogen uptake in wheat were studied in a two-year continuous experiment from 2006 to 2008 with four cropping systems, including two sole cropping systems (wheat–soybean and wheat–sweet potato) and two rely cropping systems (wheat/maize/soybean and wheat/maize/sweet potato). In the wheat/maize/soybean system, the soil moisture, soil pH and soil quick-acting N (NO3?-N and NH4+-N) content at wheat rhizosphere reduced at both flowering and ma-turity stages, and the total nitrogen uptake in shoots, root activity, root dry matter weight and soil total nitrogen content of wheat increased. At flowering stage, the total amount of organic acids and the content of soluble sugar of wheat rhizosphere increased in the wheat/maize/soybean system. The total amount of organic acid and the content of soluble sugar of wheat were higher in relay cropping system than in sole cropping system. In the two sole cropping systems, the wheat–soybean mode had higher amount of organic acid and higher content of soluble sugar than wheat–sweet potato. Wheat plants from fringe rows could exude organic acids and higher soluble sugar content than those from central rows, and the amount of root exudates in fringe rows was the high-est among all the cropping systems. At jointing stage, the content of acetic acid in the sole cropping systems increased, which accounted for 47.8% to 51.6% of the total of organic acid. The content of citric acid in the relay cropping systems increased from 31.7% to 55.1% of total organic acid. At flowering stage, the content of acetic acid in sole and relay cropping systems was also promoted from 33.3% to 78.3% of the total organic acid. The root exudates were in favor of improving root growth condition, activating soil nutrition, enhancing nitrogen uptake and increasing nitrogen use efficiency in the wheat/maize/soybean relay crop-ping system.

Effect of Shallow Water Management on Growth and Yield of Rice

Rice, the most staple food crop of the world has been cultivated about 157 million hectares of land (FAO, 2008). Irrigated rice ecosystem contributes 75% of global rice production. Growing rice using conventional irrigation (continuous flooding) requires a tremendous amount of water. The high water demand of irrigated lowland rice mainly arises from keeping the field continuously submerged. There is decreasing trend in water resource availability year by year due to various reasons. The shortage of water resources for rice production has now become an important issue worldwide. It indicates that a reduction in water input without compromising yield and optimization of scarce water in rice production are required. Shallow water management can be one of the alternatives to use water efficiently, achieve good yield and minimize the methane emission from the rice fields. However, information about growth and yield of rice grown under shallow water management are limited. Therefore, this study was conducted to investigate whether shallow water could influence plant growth and yield of irrigated rice under field conditions. Materials and Methods A field experiment was conducted at Yamagata University Experimental Farm, Takasaka, Tsuruoka, Japan in 2009. Two plant spacings – [30*30cm (wider) and 30*15cm (narrow)] and water managements shallow and conventional were practiced .The four treatments were set up as conventional wider (CW), conventional narrow (CN), shallow wider (SW) and shallow narrow (SN). In conventional method, five to six cm water ponding depth was maintained throughout the growing period except for mid season drainage and totally drained out 15 days before the harvest. For shallow water ,ponding water depth of 1-2cm with wetting and drying was done till panicle initiation stage and then 1-2 cm was maintained and totally drained out 30 days before harvesting. Transplanting of 28 days old (3.5leaf age) seedlings of Sasanishiki variety was done on12th May and harvested on 1 st October 2009. The total dry matter & nitrogen (N) uptake by plant was measured at 37, 44, 51, 58, 65, 77, 91 and 122 days after transplanting (DAT). The yield was estimated by both yield components (10hills) and yield examination (50hills).This preliminary experiment was carried without replication. Results and Discussion Comparing with water management practices, aboveground biomass was higher in shallow than conventional. Interestingly, wider spacing of shallow water management showed almost same as to conventional narrow spacing (fig.1).

BIOMASS ACCUMULATION IN OPUNTIA FICUS-INDICA (L.) MILL PLANTS GROWN IN A CLOSED HYDROPONIC SYSTEM

The research was carried out at the Hydroponic Station of the Agronomy School of the Universidad Autonoma de Nuevo Leon, in Marin, NL Mexico. Tender pad cactus (Opuntia ficus-indica L. Mill.) cultivar 'Villanueva' was planted at a density of 16 plants m -2 . The aims of this study were: a) to estimate the tender pad cactus yield and, b) to determinate the increment of the fresh weight, dry matter, and nitrogen accumulation rate as a function of the air temperature (degree-days). Total cactus yield at 56 days after plantation, based on the fresh weight and dry matter production was 4.265 kg m -2 and 0.2252 kg m -2 , respectively, while the total nitrogen uptake in the same period was 4.36 kg m -2 . The relationship of fresh weight, dry matter and nitrogen uptake to degree-days was a first degree polynomial with R 2 0.9924, 0.9948, and 0.9887 (p<0.001) determination coefficient per research parameter, respectively. The increased production rate of fresh tender pad cactus and dry matter content was 0.004 and 0.0002 kg m -2 (degree-days) -1 , respectively while the nitrogen accumulation rate was estimated to be 0.0228 g m -2 (degree-days) -1 .

하수처리수 및 폐양액의 재이용이 배추 유묘 생장에 미치는 영향

기후변화로 인해 발생될 수 있는 물 부족 현상에 대응하기 위하여 기존 농업용수에 대한 대체용수로 하수처리수 및 폐양액의 재이용이 유식물 생장에 미치는 영향을 평가하였다. 하수처리수와 폐양액에 대한 수질분석결과 유기배지로부터의 폐양액은 무기배지로부터의 폐양액 및 하수처리수와 비교해서 보다 많은 양분을 함유하고 있었으며 하수처리수에서는 <TEX>$Na^+$</TEX>과 <TEX>$Cl^-$</TEX> 함량이 다른 용수보다 높은 것으로 나타났다. 배추묘의 생육은 폐양액 처리구에서 대조구인 지하수 처리구에 비해 유사하거나 촉진되었고 하수처리수 처리구에서는 대조구와 비슷하게 나타났다. 육묘기간 동안 배추묘가 흡수한 질소는 관행재배에서 5.47 mg/plant 이었으며, 유기배지와 무기배지로부터의 폐양액 처리구에서 각각 10.02 mg/plant, 5.20 mg/plant인 것으로 나타났다. 하수처리수 처리구에서는 배추의 질소함량이 4.59 mg/plant으로 나타났다. 관행의 1/2 수준으로 시비하고 유기배지로부터의 폐양액을 처리한 배추의 질소 흡수량은 8.34 mg/plant으로 관행재배보다 높은 것으로 나타나 폐양액 이용 시 육묘에 이용되는 비료의 시용을 줄여야 할 것으로 판단된다. 한편 배추의 인 함량은 관행재배에서 8.9 <TEX>${\mu}$</TEX>g/plant로 나타났으며 유기배지로부터의 폐양액 처리구에서도 관행재배와 비슷한 수준이었다. 반면 인 함량이 낮았던 무기배지로부터의 폐양액과 하수처리수 처리구에서 배추가 흡수한 인산 함량이 가장 높은 것으로 나타났다. 배추묘가 흡수한 양이온의 경우 관행재배에 비해 폐양액과 하수처리수 처리구에서 상대적으로 많은 양을 흡수하였다. 이상의 결과로부터 선정된 폐양액 및 하수처리수에 대한 농업용수로써의 재이용 가능성을 확인할 수 있었으며 향후 현장실험을 통해 작물의 생육특성 및 생산량 평가를 실시하고 대체용수 사용에 따른 환경영향을 평가하는 연구가 진행되어야 할 것으로 판단된다. Water shortages are expected to be a major impact of climate change. This study examined the growth of Chinese cabbage seedling using reclaimed wastewater and waste nutrient solution as alternative irrigation resources. Generally, the concentration of nutrients, such as <TEX>$K^+$</TEX>, <TEX>$NH_4^+$</TEX>, <TEX>$Mg^{2+}$</TEX>, <TEX>$Ca^{2+}$</TEX>, <TEX>$Cl^-$</TEX>,<TEX>$NO_3^-$</TEX>, <TEX>$PO_4^-$</TEX> and <TEX>$SO_4^{2-}$</TEX>, in waste nutrient solution was higher than that in wastewater. However, Chinese cabbage seedling irrigated with wastewater was supplied a higher concentration of <TEX>$Na^+$</TEX> and <TEX>$Cl^-$</TEX> than waste nutrient solution. The growth of Chinese cabbage seedling irrigated with waste nutrient solution was similar or higher than those irrigated with groundwater as control, while the growth of those irrigated with wastewater was similar to those irrigated with groundwater. The total nitrogen uptake in Chinese cabbage seedling irrigated with groundwater, waste nutrient solution from organic and inorganic hydroponic cultures, and wastewater was 5.47, 10.02, 5.20, and 4.59 mg/plant, respectively. The nitrogen uptake of Chinese cabbage seedling irrigated with waste nutrient solution from organic hydroponic substrates in a 50% lower dose than recommended was 8.34 mg/plant, which is higher than that of the cabbage irrigated with groundwater. Overall, the results suggest that waste nutrient solution and wastewater can be used as alternate water resources, and can allow a reduction in the amount of fertilizer needed to raise Chinese cabbage seedling.

Evaluation of Tillage Systems for Grain Sorghum and Wheat Yields and Total Nitrogen Uptake in the Texas Blackland Prairie

Recently, there has been an increased interest in cropping systems such as conservation-tillage; however, determining the best alternative between cropping system options is often complicated by disparities in research results due to seasonal variability. The economic cost of the systems further complicates the determination of the best alternative for sustainable crop production. To evaluate tillage systems using experimental data, a computer simulation approach called fuzzy multi-attributive decision-making (MAMD) can be applied. In this study, MAMD was applied to research the impact of conservation tillage and conventional tillage systems with and without raised wide beds on yield and nitrogen (N) uptake in grain sorghum and wheat for soils of the Texas Blackland Prairie. Results of yield and N uptake data for 4 years (1994–1997) indicated that the various tillage systems had merits and demerits across the different years of study. The economic conditions of the cropping systems were also utilized in the evaluation. Utilization of this technique indicated that the no-tillage cropping system with wide beds was the best tillage system of the ones evaluated.

The model symbiotic association between Medicago truncatula cv. Jemalong and Rhizobium meliloti strain 2011 leads to N-stressed plants when symbiotic N2 fixation is the main N source for plant growth

A better knowledge of the nitrogen nutrition of Medicago truncatula at the whole plant level and its modulation by environmental factors is a crucial step to reach a complete understanding of legume nitrogen nutrition. This study was based on the symbiotic system that is the most commonly used by the research community (M. truncatula cv. Jemalong A17 x Rhizobium meliloti strain 2011). Plant nitrogen nutrition was analysed in relation to carbon nutrition, under a range of nitrate concentrations in the nutrient solution and different light conditions. This study shows that this 'model symbiotic association' does not allow the plant to meet its nitrogen requirements, when dinitrogen fixation is the main nitrogen source for plant growth. A strong interaction between nitrogen and carbon nutrition was shown: when plant nitrogen requirements were not sustained, plant leaf area was much affected whereas photosynthesis per unit leaf area remained relatively stable. Both total nitrogen uptake and leaf area increased with increasing nitrate concentration in the nutrient solution; the magnitude of these responses varied according to the light conditions. Interestingly, the plant nitrogen nutrition level remained nearly unaffected by the light conditions. The observed nitrogen-limitation in this 'model symbiotic association' is an important finding for the research community. Based on practical recommendations regarding both the experimental conditions and the phenotypic traits to consider, a methodological framework was proposed to (i) help genomicists to assess plant nitrogen nutrition better, and (ii) assist in the detection of new genetic variants affected for nitrogen uptake in large-scale phenotyping studies.

Changes in amino acid composition during wine vinegar production in a fully automatic pilot acetator

Changes in free amino acid, ammonium ion and urea contents in the culture medium were investigated during controlled acetification in the presence of acetic acid bacteria. The bacteria were found to use l-proline, l-leucine and ammonium ion as their primary sources of nitrogen; in fact, these three species accounted for 68.1% of their total nitrogen uptake. Concentration changes were very similar for all amino acids and consistent with changes in cell concentrations. Thus, cell concentration in the medium decreased through bacterial autolysis as the amino acid concentration increased. By contrast, when a cellular growth is produced the amino acid concentration was decreased. The concentration of acetic acid bacteria oscillated widely during the last fermentation stage. This can be ascribed to the bacteria using an apoptosis-like way in response to the stressing conditions produced by the high concentration of acetic acid present in the medium.

Light affects competition for inorganic and organic nitrogen between maize and rhizosphere microorganisms

Effects of light on the short term competition for organic and inorganic nitrogen between maize and rhizosphere microorganisms were investigated using a mixture of amino acid, ammonium and nitrate under controlled conditions. The amount and forms of N added in the three treatments was identical, but only one of the three N forms was labeled with 15N. Glycine was additionally labeled with 14C to prove its uptake by maize and incorporation into microbial biomass in an intact form. Maize out-competed microorganisms for $$^{15} {\text{NO}}_3^ - $$ during the whole experiment under low and high light intensity. Microbial uptake of 15N and 14C was not directly influenced by the light intensity, but was indirectly related to the impact the light intensity had on the plant. More $$^{15} {\text{NH}}_4^ + $$ was recovered in microbial biomass than in plants in the initial 4 h under the two light intensities, although more 15N-glycine was incorporated into microbial biomass than in plants in the initial 4 h under low light intensity. Light had a significant effect on $$^{15} {\text{NO}}_3^ - $$ uptake by maize, but no significant effects on the uptake of $$^{15} {\text{NH}}_4^ + $$ or 15N-glycine. High light intensity significantly increased plant uptake of $$^{15} {\text{NO}}_3^ - $$ and glycine 14C. Based on 14C to 15N recovery ratios of plants, intact glycine contributed at least 13% to glycine-derived nitrogen 4 h after tracer additions, but it contributed only 0.5% to total nitrogen uptake. These findings suggest that light intensity alters the competitive relationship between maize roots and rhizosphere microorganisms and that C4 cereals such as maize are able to access small amounts of intact glycine. We conclude that roots were stronger competitor than microorganisms for inorganic N, but microorganisms out competed plants during a short period for organic N, which was mineralized into inorganic N within a few hours of application to the soil and was thereafter available for root uptake.

Estimation and Mapping of Nitrogen Uptake by Forest in South Korea

Regional air pollution in northeast Asia is an emerging environmental problem requiring long-term impact assessment of acidic deposition. In this study, the gridded distribution of nitrogen uptake led by both growing forests and harvested biomass for eight tree species: Japanese Larch, Red pine, Korean pine, Oak tree, Chestnut, Other Conifers, Other broad leaved trees, and Mixed forest was identified to estimate critical loads for nitrogen over South Korea. The gridded spatial distribution of averaged nitrogen uptake was mapped by 0.125° Latitude × 0.125° Longitude resolution. The results showed that net uptake of nitrogen led by both growth and harvested biomass was totaled at 438 molc ha−1 year−1 among which harvested biomass contribution was estimated to be 25 molc ha−1 year−1, yielding a very small fraction of total nitrogen uptake presumably due to the younger stages of forest in South Korea.

Nitrogen use efficiency of sugarcane in relation to its BNF potential and population of endophytic diazotrophs at different N levels

The nitrogen fixing bacterial endophytes Gluconacetobacter diazotrophicus and Herbaspirillum spp. have been proposed to benefit sugarcane (Saccaharum spp. hybrids) growth. Variable populations of these endophytes exist depending upon ontogenic and climatic variations as well. This study investigates the effect of variable chemical nitrogen application in soil on the population of endophytic diazotrophs, acetylene reduction ability of excised roots, plant N-nutrient use efficiency and probable interactions among different parameters in eight commercial sugarcane varieties of subtropical India. Recovery efficiency (RE), agronomic efficiency (AE), partial factor productivity (PFP) and physiologic efficiency (PE) indicators were used for accounting N-nutrient use efficiency. The population of G. diazotrophicus was more at N75 compared to N0 and N150, whereas Herbaspirillum population increased from N0 to N150. ARA was positively correlated with Gluconacetobacter population in rhizosphere and root, whereas it had poor correlation with Herbaspirillum population. Positive correlation of RE and AE with ARA of roots, Gluconacetobacter and Herbaspirillum populations in roots and stems indicate their positive contribution in total nitrogen uptake by the plant per kg of N applied. Average PFP was 808.9 at N75 compared to 408.7 at N150 indicating that N was utilized efficiently at low N input status in sugarcane. Strong positive correlations of AE75 (agronomic efficiency from 75 kg N ha−1 to 150 kg N ha−1) with N-uptake (r 2 = 0.615), cane yield (r 2 = 0.758) and PFP (r 2 = 0.758) and other parameters compared to AE (agronomic efficiency from 0 kg N ha−1 to 75 kg N ha−1 or 150 kg N ha−1) correlations with N-uptake (r 2 = 0.111), cane yield (r 2 = 0.368) and PFP (r 2 = 0.190) indicated that the AE of sugarcane was strongly directed towards producing more cane yield per unit of N fertilizer once the sugarcane plant has established using initial dose of nitrogen and thus AE75 seems to be a more appropriate indicator for accounting N-nutrient use efficiency in sugarcane.

New and regenerated production during a late summer bloom in an Arctic polynya

New and regenerated production were estimated from nitrate, ammonium and urea uptake in the highly productive North Water region (NOW, northern Baffin Bay) during the late summer bloom and its decline in early autumn 1999. Nitrogen uptake rates decreased due to a significant 4-fold reduction of the average irradiance in the euphotic zone between these 2 periods. Nitrate availability also regulated the relative uptake of nitrate (ratio of nitrate uptake to total nitrogen uptake, or f-ratio) over spatial scales in early autumn. Stations located along the Greenland coast, which had relatively warm (-0.5°C) and saline (32.5) waters, had higher nitrate concentrations (153 vs. 51 mmol N m -2 ) and f-ratios (0.36 vs. 0.16) than those of stations located on the Canadian side, where the euphotic zone was relatively colder (-1.4°C) and less saline (30.6). The f-ratios were also corrected for nitrogen uptake by heterotrophic bacteria using the results from experiments that employed specific metabolic inhibitors. The corrected f-ratio range of 0.24 to 0.41 considered only the fraction of the nitrogen uptake due to phytoplankton in order to obtain a more accurate estimate of new production. Based on this range, new production varied from 203 to 346 and 85 to 145 mg C m -2 d -1 in late summer and early autumn, respectively. For the entire sampling period, averaged new production was 132 to 228 mg C m -2 d -1 ; however, when the dissolved form was included, we estimated that new production may double to between 262 and 452 mg C m -2 d -1 . This estimate illustrates that dissolved forms can be significant and need to be considered. When combining our results with those from the literature, new production in the NOW in 1998 - 99 amounted to between 143 and 152 g C m -2 yr -1 , suggesting that 60% of the total annual primary production may potentially be exported from the euphotic zone. This study completes the first annual time series of new production in a high-latitude ecosystem.

Seasonal and interannual variability in phytoplankton and nutrient dynamics along Line P in the NE subarctic Pacific

We analysed mixed-layer seasonal and interannual variability in phytoplankton biomass and macronutrient (NO 3 and Si(OH) 4) concentrations from three decades of observations, and nitrogen uptake rates from the 1990s along Line P in the NE subarctic Pacific. Chlorophyll a concentrations near 0.35 mg m −3 were observed year-round along Line P except at the nearshore station (P4) where chlorophyll a concentrations in spring were on average 2.4 times the winter values. In contrast, the temporal variability in carbon-to-chlorophyll ratios at the two main end members of Line P (P4 and OSP) was high. Large seasonal and interannual variability in NO 3 and Si(OH) 4 concentration were observed along Line P. Highest upper mixed-layer (top 15 m) nutrient concentrations occurred on the continental shelf in late summer and early fall due to seasonal coastal upwelling. Beyond the shelf, maximum nutrient concentrations increased gradually offshore, and were highest in late winter and early spring due to mixing by winter storms. Interannual variations in upper mixed-layer nutrient concentrations beyond the shelf (>128°W) were correlated with E–W winds and the PDO since 1988 but were not correlated with either climate index between 1973 and 1981. Despite differences in nutrient concentration, nutrient utilization (ΔNO 3 and ΔSi(OH) 4) during the growing season were about 7.5 μM at all offshore stations. Variations in ΔNO 3 were correlated with those of ΔSi(OH) 4. The annual cycle of absolute NO 3 uptake (ρNO 3) and NH 4 uptake (ρNH 4) rates by phytoplankton in the upper mixed-layer showed a weak increasing trend from winter to spring/summer for the period 1992–1997. Rates were more variable at the nearshore station (P4). Rates of ρNO 3 were low along the entire line despite abundant NO 3 and low iron (Fe), at the offshore portion of Line P and sufficient Fe at the nearshore station (P4). As a result, new production contributed on average to only 32 ± 15% of the total nitrogen (N) uptake along Line P. NO 3 utilization in the NE subarctic Pacific is probably controlled by a combination of environmental variables, including Fe, light and ambient NH 4 levels. Elevated ambient NH 4 concentrations seem to decrease the rates of new production (and f-ratios) in surface waters of the oceanic subarctic NE Pacific. Contrary to expectation, phytoplankton biomass, nutrient utilization (ΔNO 3 and ΔSi(OH) 4), and nitrogen uptake (ρNO 3 + ρNH 4) varied relatively little along Line P, despite significant differences in the factors controlling phytoplankton composition assemblages and production. Future studies would benefit from including other variables, especially light limitation, to improve our understanding of the seasonal and interannual variability in phytoplankton biomass and nutrients in this region.

MODELING MACRONUTRIENT ABSORPTION OF HYDROPONICALLY-GROWN CUT FLOWER ROSES

Regulations increasingly limit the water run-off allowed from agricultural facilities. A better understanding of appropriate irrigation and fertilization regimes are needed to comply with these regulations. The objectives of this project were to determine how macronutrient absorption by roses varies in relationship to growth of new flower stems and test whether an existing mathematical model is suitable for describing nitrogen and potassium uptake across a crop cycle. Absorption of ammonium (NH4 + ), nitrate (NO3 - ), potassium (K + ), calcium (Ca 2+ ), and magnesium (Mg 2+ ) by rose plants (Rosa × hybrida ‘Kardinal’) were measured during three crop cycles. Following a harvest, the rate of total nitrogen (N) uptake decreased to 0.15 mmol d -1 g -1 harvested dry weight (HDW) where it remained for the first five days, decreased during days 8-10, and then increased in synchrony with flower stem elongation. K + uptake rates gradually declined for the first 12 days following a harvest cycle, then increased in synchrony with stem elongation to maximum uptake rates of 0.05 to 0.09 mmol d -1 g -1 HDW as stems reached maturity. Prior to harvest, the rate of Ca 2+ uptake decreased and remained low until day 7 of the new cycle (appearance of new shoots), then increased until just prior to stem maturity. Mg 2+ uptake rate increased in synchrony with stem elongation and then decreased just prior to harvest. Simulations of the N/K + model accurately predicted the increase in N and K + uptake rates beginning around day 10-12 and proceeding until harvest as well as the drop in N and K + uptake occurring at harvest. The simulation does not predict the somewhat sustained uptake rates for the first 7-10 days following harvest and the decline in uptake during early stem elongation. The most likely reason for the discrepancy is that the model does not yet have mechanisms for handling redistribution of these nutrients from perennial tissues to new growing shoots or account for changes in root growth across a crop cycle.

Trends since 1900 in the yield potential of Italian-bred durum wheat cultivars

Changes in yield potential brought about by durum wheat breeding in Italy can be used to define future breeding objectives for durum improvement in Mediterranean environments. The grain yield of 20 durum wheat cultivars, grouped according to their period of release, into ‘old’ (up to 1950), ‘intermediate’ (1950–1973) and ‘modern’ (1974–2000), was compared in an irrigated 2-year field trial, in which two sowing dates and two nitrogen fertilisation rates were imposed. The grain yield of the intermediate cultivars was 39% higher than that of those in the old group, but 18% less than that of the modern material. This increase was associated with earliness, kernel number, harvest index and total nitrogen uptake. Total above-ground biomass and individual kernel weight, on the other hand, were largely unaffected by breeding. Sowing date did not affect the ranking of cultivars, although the more modern cultivars benefited most from the availability of more soil nitrogen. By accessing syriacum germplasm, Italian breeders achieved a substantial improvement in the earliness and productivity of durum wheat well before the introduction of Rht genes. The introduction of dwarfing genes reduced lodging susceptibility, increased harvest index, and marginally delayed flowering time. Modern cultivars also out-performed their predecessors both when sown later and when provided with suboptimal levels of N fertiliser.

Effect of Integrated Nutrient Application in Chickpea+Mustard Intercropping System in the Semi‐arid Tropics of North India

Chickpea+mustard is a prominent intercropping system in Indian sub continent. The majority of the farmers adopt this system under resource constraint conditions. The integrated applications of fertilizers with organic compost and biofertilizers are considered essential for the sustainability of a system. Looking to lack of information on this aspect, a study was undertaken on ‘Typic Ustochrept’ soils found commonly in the North Plain Zone of India. Results revealed that integrated nutrient application (INA) [50% recommended dose of fertilizer (RDF)+FYM at 5 t ha−1+biofertilizers (Rhizobium+PSB)] significantly enhanced average plant height, crop biomass, leaf area index, number and dry weight of root nodules of chickpea and plant height and crop biomass in mustard as compared to control. INA also produced significantly more grain and biological yield of chickpea and mustard and more chickpea equivalent yield (2664 kg ha−1) and net return (US $617 ha−1) as compared to control grown under intercropping system. INA also significantly increased the NPK content in shoot and grain of chickpea and mustard as compared to control causing significantly higher total uptake of nitrogen, phosphorus and potassium in chickpea and mustard. This treatment also made available more nitrogen, phosphorus and potassium in the soil after the harvest of crop in comparison to chickpea+mustard intercropping system under moisture stress conditions.

EFFECT OF COMPOUND SULPHER FERTILIZER ADDITION ON THE GROWTH AND YIELD FOR SUNFLOWER Helianthus annuus L.

Two field experiments were carried out at the college of agriculture - university of Al-Anbar in spring season of 2001 and 2002 years. To study the effect of three treatments. The first was application of agricultural sulpher at level 2 Meq S°. ha-1 (T1) the second was application phosphorus and nitrogen at level 240 kg P2O5 . h-1 and 180 kg N. ha-1 respectively (T2), and third treatment was application compound sulpheric fertilizer (6 : 19 : 65) (N : P2O5 : S) to soil with level 3 Meq. ha-1 (T3). Which replicated third time on growth and productivity of sunflower (Euro-flower hybrid) and to limitation the fertilizer efficiency for production. Same chemical properties of rizosphere soil were determined with crop growth parameters and total uptake of nitrogen also phosphours during flowering and maturation stages. Addition to yield properties. The results were showed significantly superiority for T3 treatment in reduction the soil pH and increasing soil EC also soil content from nitrogen and available phosphors with increasing them uptake at the two studied stage of plant growth during the two years. Which positively reflect on growth parameters (plant height, leaf area and plant dry matter) also yield components, head diameter, number of seeds per head and total seeds yield. which superiority with 27.3 and 10.65 % portion on T1 during the two studied years respectively. Oil contains and its yield was increased at T3 treatment also. Which gets best fertilizer efficiency for production reached 19.8 % as average in comparison to T1. the results were showed that addition of sulpher with crop recommendation of nutrients more efficiency to increase the yield which reflected the importance in improvement of nutrient availability when we added it to the soil as fertilizer.

Nitrogen removal by phytoplankton uptake through a temperate non-turbid estuary

The impact of phytoplankton growth on the ambient levels of nitrate, ammonium and urea at three stations in the Southampton Water estuarine system was assessed over the productive spring–summer period in 2001 using 15N tracer techniques. The relative contribution of the different nitrogen sources to total nitrogen uptake was also addressed. In general, ammonium uptake contributed >60% to total nitrogen uptake, but on some dates nitrate and urea uptake were dominant. Nitrogen depletion rates show that phytoplankton activity can, respectively, remove nitrate, ammonium and urea from the euphotic water column at rates of up to 9, 28 and 51% h −1 of the ambient levels. Area-wide N-uptake estimations suggest that over time scales of hours to a few days, uptake by phytoplankton can potentially remove 100% of riverine nitrogen loads during the productive period. Mass balance calculations suggest that 13 and 36% of the nitrate and 80 and 68% of the ammonium annual inputs to the Test and Southampton Water (SW) estuaries are respectively removed. N-removal however, was less significant than N-export from the system. Estimates indicate that >100% and approximately 70% of nitrate and ammonium inputs are respectively exported from the Test and SW estuaries to the adjacent estuary and to the Solent. It appears that nitrification, ammonium regeneration and wastewater inputs can account for the extra nitrogen within the system.

Effects of Farmyard Manure and Inorganic Fertilizers on Sorghum Growth, Yield, and Nitrogen Use in a Semi-Arid Area of Ethiopia

ABSTRACT A field experiment was conducted to assess the effect of the combined use of farmyard manure and inorganic fertilizer on the growth and yield of sorghum and on soil chemical properties in a semi-arid area in northeastern Ethiopia. Twelve treatments comprising factorial combinations of four levels of farmyard manure (0, 5, 10, and 15 t ha−1) and three levels of inorganic fertilizers (0%, 50%, and 100% of the recommended rate) were compared in a randomized complete block design with three replications over a period of six years. The results revealed significant improvements in the growth and yield of sorghum due to the main and interaction effects of farmyard manure and inorganic fertilizer application. The combined application of farmyard manure and inorganic fertilizers increased post-anthesis dry-matter production by 147%–390% and grain yield by 14%–36%. The main effects of farmyard manure and inorganic fertilizers increased stover yield by 8%–21% and 14%–21%, respectively. Farmyard manure application increased total nitrogen (N) uptake by 21%–36%, grain protein yield by 8%–11%, and grain protein concentration by 20%–29%. Application of farmyard manure along with 50% of the recommended inorganic fertilizer rate resulted in a grain yield equivalent to, or greater than that for 100% of the recommended inorganic fertilizer rate, thus effecting a 50% savings of inorganic N and phosphorus (P) fertilizer. Application of 5, 10, and 15 t farmyard manure ha−1along with 100% of the recommended fertilizer rate and 5, 10, and 15 t farmyard manure ha−1 along with 50% of the recommended fertilizer rate can be recommended for farmers who can and cannot afford to buy inorganic fertilizers, respectively.