Increased Nitrogen Levels Research Articles

EFFECT OF SEEDING RATES, NITROGEN LEVELS AND HARVESTING DATES ON GROWTH, YIELD AND QUALITY OF JUTE (Corchorus capsularis, L.)

This investigation was carried out at the experimental farm of Sakha Agric. Res. Station during 2007 and 2008 seasons to study the effect of three seeding rates at 4, 5 and 6 kg/fed, three nitrogen levels 20, 30 and 40 kg/fed and two harvesting dates i.e., after 120 and 150 days from sowing on growth, yield quantity and quality of U.P.C. 94 jute cultivar. The main findings of the present study could be summarized as follows: The seeding rate at 5 kg/fed combined with the plant age at 102 days from sowing achieved the highest mean values of dry weight/plant (g), plant height (cm) and leaf area/plant (dm2), while, the leaf area index was in high magnitude by using 6 kg seeds/fed at 72 days old in both seasons. Planting jute with 4 kg/fed at the growth period of 87-102 days from sowing performed the highest average for CGR, RGR and NAR. The maximum contents of chlorophyll A, B and A + B occurred due to the seeding rate of 4 kg/fed at the two plant ages either 55 or 75 days from sowing, as well as, increased number of capsules/plant, seed index, seed yield/plant and fiber yield/plant in both seasons. Whereas, the highest means of capsules zone length, green yield/plant, fiber yield/fed, fiber percentage and fiber strength were obtained by sowing at the rate of 5 kg/fed, while planting with 6 kg/fed accomplished the highest estimates for technical length, fiber length and fiber fineness in both seasons. There was gradual increase in dry weight/plant due to increasing nitrogen level from 20 up to 40 kg/fed. This trait also increased when plant age increased from 57 to 102 days old, but the maximum estimates of plant height (cm), leaf area/plant (dm2) and leaf area index were obtained due to application of 30 kg N/fed when jute plants reached 102 days from sowing. The more estimates of CGR and NAR were obtained by applying 20 kg N/fed and at the growth period of 87-102 days old, while, the highest RGR was obtained by adding either 30 or 40 kg N/fed and during the growth period of 57-72 days old in both seasons. Gradual increment happened in each of chlorophyll A, B and A + B with increasing nitrogen level at the smallest age i.e., 55 days old. There were gradual increments for each green yield (ton), seed yield (kg) and their components in addition to fiber yield/fed (kg) with increasing N level up to 40 kg/fed, but reduction occurred in fiber percentage and fiber fineness in this case in both seasons. Delaying harvesting date to 150 days from sowing caused remarkable increase in all studied characters except that of fiber percentage, fiber strength and fiber fineness which were decreased in this case and as compared with the harvesting date of 120 days from sowing.

Water Quality Trends (1970 to 2005) Along Delaware Streams in the Delaware and Chesapeake Bay Watersheds, USA

Water quality trends from 1970 to 2005 were defined along 30 Delaware streams in the Delaware and Chesapeake Bay watersheds in the USA. Water quality improved or was constant at 69% of stations since 1990 and at 80% of stations since 1970/1980. Dissolved oxygen (DO) improved or was constant at 73% of streams since 1990 and 32% of streams since 1970/1980. Total suspended sediment improved or was constant at 75% of streams since 1990 and 100% of streams since 1970/1980. Enterococcus bacteria improved or remained constant at 80% of streams since 1990 and 93% of streams since 1970/1980. Total Kjeldahl nitrogen improved or was constant at 48% of streams since 1990 and 100% of streams since 1970/1980. Total phosphorus improved or was constant at 66% of streams since 1990 and 85% of streams since 1970/1980. During 2001–2005, median levels were good or fair at 100% of the stations for DO, 78% for sediment, 50% for bacteria, 59% for nitrogen, and 56% for phosphorus. Good water quality correlates with high amounts of forest area (>25%) in Delaware watersheds. Since the Federal Clean Water Act Amendments of the 1970s, improving Delaware water quality stations (50) outnumbered degrading stations (23) by a 2:1 margin. Since 1990, degrading water quality stations (46) exceeded improving stations (38) mostly due to deteriorating nitrogen levels in half of Delaware streams, a reversal from early gains achieved since the 1970s. Over the last three and a half decades, watershed strategies have improved or preserved water quality along Delaware streams; however, greater emphasis is needed to curb recently resurging increases in nitrogen levels.

재배조건(이앙시기, 수확시기, 질소시비)별 쌀의 무기질 조성 비교

Dept. of Holticulture, Chungnam National University, Daejon 305-764, KoreaAbstractThe objectives of this study were to analyze mineral contents of three rice varieties (Josangheugchal, Heugjinjubyeo and Dongjinchalbyeo) under three different cultural practices: five transplanting time (May 15, May 25, June 4, June 14, and June 24), five harvest times (30, 40, 50, 60, and 70 days) and N-fertilization levels (0.0, 4.5, 9.0, 13.5, and 18.0 kg/10a). Mineral contents of Josangheugchal were increased by late trans-planting time with increased nitrogen level; however, it was not significantly different by harvest time. Heugjinjubyeo did not show significant difference in three cultivations. Mineral contents of Dongjinchalbyeo increased at the transplanting time of May 25 and June 14 and according to late harvest time. Also mineral contents of Dongjinchalbyeo that did not show significant difference except for calcium according to different nitrogen levels.Key words: mineral, rice quality, transplanting time, five harvest time, N-fertilization level

Effects of elevated nitrogen deposition on soil microbial biomass carbon in major subtropical forests of southern China

The effects of elevated nitrogen deposition on soil microbial biomass carbon (C) and extractable dissolved organic carbon (DOC) in three types of forest of southern China were studied in November, 2004 and June, 2006. Plots were established in a pine forest (PF), a mixed pine and broad-leaved forest (MF) and monsoon evergreen broad-leaved forest (MEBF) in the Dinghushan Nature Reserve. Nitrogen treatments included a control (no N addition), low N (50 kg N/(hm2·a)), medium N (100 kg N/(hm2·a)) and high N (150 kg N/(hm2·a)). Microbial biomass C and extractable DOC were determined using a chloroform fumigation-extraction method. Results indicate that microbial biomass C and extractable DOC were higher in June, 2006 than in November, 2004 and higher in the MEBF than in the PF or the MF. The response of soil microbial biomass C and extractable DOC to nitrogen deposition varied depending on the forest type and the level of nitrogen treatment. In the PF or MF forests, no significantly different effects of nitrogen addition were found on soil microbial biomass C and extractable DOC. In the MEBF, however, the soil microbial biomass C generally decreased with increased nitrogen levels and high nitrogen addition significantly reduced soil microbial biomass C. The response of soil extractable DOC to added nitrogen in the MEBF shows the opposite trend to soil microbial biomass C. These results suggest that nitrogen deposition may increase the accumulation of soil organic carbon in the MEBF in the study region.

EFFECT OF CROPPING SYSTEMS AND NITROGEN FERTILIZATION LEVELS ON GROWTH AD YIELD OF GIZA 168 WHEAT CULTIVAR

Two field experiments were carried out during the two successive seasons of 2005/06 and 2006/07 at Agricultural Research Station, Faculty of Agriculture, AlexandriaUniversity, to evaluate Giza 168 wheat cultivar response to different cropping systems and nitrogen fertilizer levels. The results indicated that, cropping systems including one cut type berseem and/ or soybean significantly decreased weeds dry weight and increased number of tillers and spikes per square meter, 1000-grain weight and grain yield per feddan in the two seasons. Increasing nitrogen levels up to 80 kg per feddan, significantly decreased weeds dry weight and increased plant height, number of tillers and spikes per square meter, spike length, grain weight, number of grains per spike, 1000- grain weight and grain yield per feddan in both seasons. Application of 80 kg N/ fed. to the cropping systems containing leguminous crops especially the one cut berssem and soybean produced the heaviest grains, highest number of tillers per square meter and grain yield per feddan in the first, second and both seasons, respectively.

PRODUCTIVITY OF WHEAT AS AFFECTED BY IRRIGATION SYSTEMS, NITROGEN LEVELS AND FOLIAR APPLICATION UNDER NEWLY RECLAIMED SANDY SOILS

Two field experiments were conducted at the Experimental Station Farm in Kalabsho and Zayian Region, Faculty of Agriculture, Mansoura University during the two successive winter seasons of 2004/2005 and 2006/2007 to determine the effect of two irrigation systems (flooding and sprinkling), four nitrogen levels (60, 80, 100 and 120 kg N/fed) and foliar application with some commercial compounds (Nervatin-vet and Maxifert) as well as their interactions on growth, yield and its components and quality of wheat (Triticum aestivum, L.) Sakha 93 cultivar. The main results of this study can be summarized as follows: Irrigation of wheat plants through sprinkling method significantly increased all studied characters as compared with flooding irrigation in both seasons. Concerning the effect of nitrogen fertilizer levels the all studied characters were remarkably increased as a result of increasing nitrogen levels from 60 up to 120 kg N/fed in both seasons. Application of foliar compound containing macro and micro elements (Nervatin-vet) resulted in a significant increased in grain yield and straw yields and its components as compared with the compound containing microelements alone (Maxifert) and control treatment in both seasons. Maxifert exceeded control treatment in all studied characters. It can be concluded that in order to maximizing wheat crop productivity it must be irrigated through sprinkling irrigation system and mineral fertilized with 120 kg N/fad as well as foliar fertilized with some commercial nutrient compounds that contain macro and micro elements such as Nervatin-vet under the environmental conditions of Kalabsho and Zayian district as a newly reclaimed sandy soils.

YIELD AND QUALITY OF TWO FLAX VARIETIES AS AFFECTED BY FOLIAR SPRAYING WITH POTASSIN RATES AND NITROGEN LEVELS UNDER SANDY SOIL CONDITION

Two field experiments were performed at the Experimental Farm, Esmailia Agric. Res. Station Agric. Res. Center, Esmailia Governorate, Egypt during the two growing seasons of 2003/2004 and 2004/2005 to study the influence of foliar spraying of potassin rates at (1 and 1.5 liters potassin/fed.) and the three nitrogen levels of 25, 50 and 75 kg N/fed. on yield, yield components and some technological characters of the two flax varieties Sakha 1 and Sakha 2. Moreover, simple correlation coefficient among straw and seed yields and their components as well as fiber yield and its quality were studied. Results obtained could be summarized as follows: The flax variety Sakha 1 surpass Sakha 2 in total length, technical length, straw yield/plant as well as per feddan, fiber yield/plant as well as per feddan, fiber length and fiber fineness in both seasons in addition to the combined analysis over them. Fiber percentage had similar trend except with only the second season where Sakha 2 superior over Sakha 1 in this case without significance. The flax variety Sakha 2 ranked first in no. of fruiting branches, no. of capsules/plant, no. of seeds/capsule, 1000 seed weight, seed yield/plant as well as per feddan, seed oil percentage and oil yield/fed. Foliar spraying with potassin at the rate of 1.5 liter/fed. achieved maximum mean values of all straw and seed characters under study, except with fiber fineness trait, which recorded highest estimates by spraying with 1 liter, these results were true in both seasons and the combined data. There was gradual increment in straw and seed yields in addition to their components with increasing nitrogen levels from 25 towards the highest dose at 75 kg N/fed., except with fiber fineness trait which more fine fiber obtained by applying 25 kg N/fed. and more coarse fiber occurred with increasing nitrogen levels towards the highest level. Straw yield/plant was highly significant and positive correlated with each of total length, technical length, fiber yield/plant, fiber yield/feddan and fiber length. Also, the r values were highly significant and positive between seed yield and either no. of capsules/plant or 1000 seed weight.

Evaluation of a mature lodgepole pine stand's resistance to the current mountain pine beetle infestation after nitrogen fertilization

Research is currently under way in the Southern Interior Forest Region to determine whether nitrogen fertilization can be used to increase mature lodgepole pine trees' natural defences against the mountain pine beetle (MPB) and thereby reduce the impact of the mpb infestation in pine stands. In fall 2006, three nitrogen fertilizer treatments (0, 200, and 400 kg N/ha) were applied randomly to each of 10 plots in a 140-year-old fire-regenerated stand of mixed lodgepole pine, spruce, and true fir. In 2007, the stand was inoculated with two isolates of blue stain fungus and with local beetle microflora. A forest health survey helped determine the level of MPB within the stand before the plot centres were baited with pheromones. Early results show that the 400 kg N/ha treatment significantly increased nitrogen levels in pine phloem and needles. No significant differences were apparent in lesion length related to nitrogen treatment levels within each of the three fungal isolates. Measurements in 2008 will show whether MPB attack success varies among nitrogen treatments.

Response of Lachenalia growing in soil to nitrogen fertilisation during the pot plant phase

Lachenalia bulbs used in the pot plant industry are produced in the nursery phase from bulblets propagated from leaf cuttings. Fertilisation during this phase of enlargement can ultimately influence the growth and flowering of pot plants through the nutritional status of the bulbs. The objective of this study was to determine the response of cultivars (Rupert and Ronina) in the pot plant phase to different nitrogen levels when grown from bulbs whereof the fertilisation history is known. During the nursery phase bulblets of cultivars Rupert and Ronina received three nitrogen levels (0, 250 and 520 kg N ha−1) combined with two different application times. The resulting bulbs were planted in the pot plant phase and five nitrogen levels (0, 70, 180, 330 and 520 kg N ha−1) applied. Ronina leaf area responded better than Rupert when fertilised in the pot plant phase. The leaf area was also promoted by nitrogen applied in the nursery phase. Nitrogen applied in the nursery and pot plant phases influenced the number of florets formed per inflorescence positively. Only high nitrogen levels applied in the nursery phase (250 and 520 kg N ha−1) increased the peduncle length of the plants. Peduncle diameter was increased with an increase in nitrogen levels in the nursery phase as well as in the pot plant phase. This trial showed that Lachenalia has a low nitrogen requirement in the pot plant phase when grown from bulbs that were properly fertilised in the nursery phase but additional fertiliser in the pot plant phase improved the quality of the inflorescence.

PARÂMETROS NUTRICIONAIS DO CAPIM-TANZÂNIA SOB DOSES CRESCENTES DE NITROGÊNIO EM DIFERENTES IDADES DE CORTE

The objective this experiment was to evaluate the chemical composition and in vitro dry matter digestibility of Tanzania grass under increasing nitrogen levels in different cutting ages, under irrigation. The treatments were three N levels (ammonium sulphate): 200, 400 and 600 kg.ha -1 for year and four cutting ages: 28; 56; 84 and 112 days. A randomized complete blocks design in factorial 3x4 arrangement (three N levels and four cutting ages, with three repetitions) was used. The analyses were accomplished using the sta-tistical System of Analysis of Variance of Data Balanced (SISVAR) program. The DM tenors didn’t differ (P 0.05) didn’t differ among the cutting ages, however they differed (P 0.05) among the cutting ages, except the 112 days, however, they differed among the N levels applied.KEY-WORDS: Chemical composition, in vitro dry matter digestibility, nitrogen fertilization.

Dietary Benefits of Fungal Associates to an Eruptive Herbivore: Potential Implications of Multiple Associates on Host Population Dynamics

We used the mountain pine beetle (Dendroctonus ponderosae Hopkins) and its two fungal associates, Grosmannia clavigera and Ophiostoma montium, to study potential nutritional benefits of fungi to bark beetles. We tested for potential effects of feeding on phloem colonized by fungi on beetle performance in field and laboratory studies. The fungi increased nitrogen levels in the phloem of attacked trees by 40%, indicating that it may be an important source of dietary nitrogen for mountain pine beetles. However, nitrogen levels of phloem inoculated with fungi in the laboratory were similar to uncolonized phloem, indicating that the fungi may redistribute nitrogen from the sapwood to the phloem rather than increase absolute levels of nitrogen. Beetles emerging from attacked trees carrying G. clavigera were larger than beetles carrying O. montium, which in turn were larger than beetles lacking fungi. Results of experimental laboratory studies varied, likely because of differences in the growth and sporulation of fungi under artificial conditions. Results indicate that the two fungi may offer complementary benefits to the mountain pine beetle because larvae preferentially fed on phloem colonized by both fungi together over phloem colonized by one fungus or uncolonized phloem. Teneral adults preemergence fed on spores in pupal chambers when they were produced and consumed little phloem before emerging. Teneral adults mined extensively in the phloem before emerging when spores were not produced in the pupal chamber. Our results provide evidence for a nutritional role of fungi in the diet of bark beetles and show that multiple associates may differentially affect beetle performance, which could have important implications for bark beetle population dynamics.

Dietary Benefits of Fungal Associates to an Eruptive Herbivore: Potential Implications of Multiple Associates on Host Population Dynamics

We used the mountain pine beetle (Dendroctonus ponderosae Hopkins) and its two fungal associates, Grosmannia clavigera and Ophiostoma montium, to study potential nutritional benefits of fungi to bark beetles. We tested for potential effects of feeding on phloem colonized by fungi on beetle performance in field and laboratory studies. The fungi increased nitrogen levels in the phloem of attacked trees by 40%, indicating that it may be an important source of dietary nitrogen for mountain pine beetles. However, nitrogen levels of phloem inoculated with fungi in the laboratory were similar to uncolonized phloem, indicating that the fungi may redistribute nitrogen from the sapwood to the phloem rather than increase absolute levels of nitrogen. Beetles emerging from attacked trees carrying G. clavigera were larger than beetles carrying O. montium, which in turn were larger than beetles lacking fungi. Results of experimental laboratory studies varied, likely because of differences in the growth and sporulation of fungi under artificial conditions. Results indicate that the two fungi may offer complementary benefits to the mountain pine beetle because larvae preferentially fed on phloem colonized by both fungi together over phloem colonized by one fungus or uncolonized phloem. Teneral adults preemergence fed on spores in pupal chambers when they were produced and consumed little phloem before emerging. Teneral adults mined extensively in the phloem before emerging when spores were not produced in the pupal chamber. Our results provide evidence for a nutritional role of fungi in the diet of bark beetles and show that multiple associates may differentially affect beetle performance, which could have important implications for bark beetle population dynamics.

EFFECT OF DIFFERENT NITROGEN LEVELS ON PRODUCTIVITY OF THREE MAIZE HYBRIDS FERTIGATION

Two field experiments were conducted in 2004 and 2005 seasons at El-Bosaily farm located at Beharia Governorate, Egypt, to study the effect of three nitrogen levels 60, 120 and 180 kg/feddan applied into irrigation water fertigation with drip irrigation system on vegetative growth, nutrient content (N, P and K) in leaves and grain and yield of three maize (Zea mays L.) hybrids (Single Cross 10, Three Way Cross 310 and Three Way Cross 324). The experiment design was a split plot with three replications where nitrogen fertilizer levels were distributed in the main plots and maize hybrids allocated in sub plots. The obtained results indicate that the increase of nitrogen level up to 180 kg /fed significantly increased plant height, number of leaves per plant, leaf area index, grain yield and straw weight. Single Cross 10 gave the significant highest vegetative growth and grain yield comparing with the other hybrids. The high-est nitrogen level (180 kg /fed) combined with Single Cross 10 gave the significantly highest grain yield and straw weight. On the other hand, 60 kg N / fed gave the highest nitrogen use effi-ciency (NUE) value followed by 120 kg N / fed The regression analysis of nutrition content (N, P, and K %) between leaf and grain was estimated. The highest regression determination coefficient (r2) was found in nitrogen percentage with r2= 0.965 followed by potassium with r2= 0.936. The lowest r2 was found in phosphorus with r2= 0.872.

Relationships Between Carbon Isotope Discrimination and Yield of Spring Wheat Under Different Water and Nitrogen Levels

ABSTRACT A greenhouse experiment was conducted to investigate the relationships between foliar carbon isotope discrimination (Δ) and above ground dry matter (ADM) at different stages during a plant's life cycle, and grain carbon isotope discrimination and grain yield (GY) at maturity of spring wheat (Triticum aestivum L.) under different nitrogen (N) and water levels. Results showed that ADM and GY both increased significantly with decreasing water stress, while the effects of nitrogen on ADM and GY varied with the water conditions. Foliar and grain carbon isotope discrimination decreased with increasing water stress and increasing nitrogen levels. For all water conditions, relationships between carbon isotope discrimination (foliar and grain) and yields (ADM and GY) were significantly positive (P < 0.001) at various growth stages. However, at the same water level, the correlations were complex, and under well-watered conditions, ADM and GY were strongly and negatively correlated with foliar and grain carbon isotope discrimination at all growth stages (P < 0.001). The correlations were inconsistent and not significant at moderate water level, but were positive under drought. Our results showed that water and nitrogen both significantly affected the relationships between yield and carbon isotope discrimination of spring wheat, that there are interactions between these two parameters, and that environmental conditions such as water and fertilizer must thus be considered in future research on the relationship between yield and carbon isotope discrimination of spring wheat.

Response of Lachenalia growing in soil to nitrogen fertilization during the nursery phase

During the nursery phase, Lachenalia flower bulb producers plant bulblets propagated from leaf cuttings, for enlargement. They strive for a high yield of good quality bulbs that are of a marketable size within a year. In this regard nitrogen is of vital importance since it stimulates vegetative growth. Very little has been known about the nitrogen requirements of Lachenalia plants that are cultivated in soil. Hence the response of two Lachenalia cultivars (Rupert and Ronina) to combinations of nine nitrogen levels (0, 30, 70, 120, 250, 330, 420 and 520 kg ha−1) and three application times (⅓ with planting and ⅔ ten weeks after planting; ⅓ with planting, ⅓ ten weeks after planting and ⅓ sixteen weeks after planting; and ¼ with planting, ¼ ten weeks after planting, ¼ sixteen weeks after planting and ¼ twenty one weeks after planting) was studied in a glasshouse using topsoil of a fine sandy loam Bainsvlei form. Nitrogen promoted the growth of Lachenalia plants irrespective of cultivar. The largest leaf area for Rupert was measured between 250 and 420 kg N ha−1 and for Ronina between 180 and 520 kg N ha−1. Both bulb circumference and firmness were influenced positive by higher nitrogen levels whereas nitrogen application time did not show such a clear trend. Bulb circumference was the largest where 330 kg N ha−1 was applied and the firmest bulbs where 420 and 520 kg N ha−1 was applied for Rupert and Ronina respectively. Nitrogen content of the bulbs increased with an increase in nitrogen levels. Bulbs that received their nitrogen in four equal applications had the highest nitrogen content. The glucose content decreased whereas the sucrose and starch content increased with higher nitrogen levels. Cultivar and nitrogen application times had variable effects on the carbohydrate content of the bulbs. The optimum nitrogen level varied between 250 and 330 kg N ha−1 and the best response was obtained when this nitrogen was applied in four equal applications throughout the season.

Effects of Different Nitrogen Levels on the Leaf Chlorophyll Content Nutrient Concentration and Nutrient Uptake Pattern of Blackgram

This study was conducted to evaluate the performance of blackgram (Vigna mungo L) under various levels of nitrogen at the Agronomy Research Site of Bangabandhu Sheikh Mujibur Rahman Agricultural University during March to June 2002. Two varieties of blackgram--BARI mash 3 and BINA mash 1 and six levels of nitrogen viz. 0, 20, 40, 60, 80 and 100 kg N ha(-1) were the treatment variables. The experiment was laid out in a RCB Design with three replications. A best-fit positive linear relationship existed between leaf chlorophyll and leaf nitrogen content with different nitrogen levels. Unexpectedly the N, P and K accumulation in the two varieties was not affected significantly. However, there was an increasing tendency of total uptake of these elements in both the varieties. N, P and K uptake increased up to 60 kg N ha(-1) then decreased with the increasing nitrogen levels. Among the varieties BARI mash 3 showed better performance than BINA mash 1 for most of the parameters.

Nitrogen concentration and nitrate/ammonium ratio affect yield and change the oxalic acid concentration and fatty acid profile of purslane (Portulaca oleracea L.) grown in a soilless culture system

AbstractPurslane is an excellent source of omega‐3 fatty acids, amino acids and vitamins. The aim of this research was to study the effect of different nitrogen levels and NO3−‐N/NH4+‐N ratios in the nutrient solution on the yield and on the oxalic acid content and fatty acid profile in purslane grown in a soilless culture system. Two experiments were carried out to test different levels of nitrogen: (1) 8–12–16 mmol L−1 and (2) 0–12–24–36 mmol L−1. A third experiment was carried out maintaining the N level fixed (12 mmol L−1) but varying the NO3−‐N/NH4+‐N ratio: 60:40, 40:60, 0:100. The results indicated that plants grew with increasing nitrogen level up to 36 mmol L−1. Nitrogen supplied in both NO3− and NH4+ forms produced bigger plants than N supplied in NH4+ form only. Nitrogen did not significantly influence the polyunsaturated fatty acid content in the canopy. Significant trends were found for α‐linolenic acid (LNA; 18:3 n‐3) and linoleic acid (LA; 18:2 n‐6), indicating a favorable accumulation of omega‐3 fatty acids with increasing N; palmitic acid decreased by increasing N and by switching the NO3−/NH4+ ratio towards the NH4+ level in the nutrient solution, but using 0:100 NO3−/NH4+, decreased plant quality. Increasing N lowered oxalic acid production and palmitic acid content, enhancing purslane nutritional quality. Keeping a high N level in the nutrient solution with a 40:60 NO3−/NH4+ ratio would give the best results in terms of yield, oxalic acid concentration and fatty acid profile. Copyright © 2006 Society of Chemical Industry

North Florida Dairy Farmer Perceptions Toward the Use of Seasonal Climate Forecast Technology

Evidence of increasing nitrogen levels in the Suwannee River Basin in North Florida demands a collaborative effort to find creative ways to reduce N pollution. This study explores the perspectives, perceptions, and attitudes of dairy farmers regarding adoption of climate forecasts as a potential way to mitigate the problem. These farmers are heavily scrutinized because of their nitrogen emissions. By contrasting scientists' pre-conceived attitudes about the usefulness of ENSO-based forecasts with dairy farmers' perceptions, gathered in a participatory and consensual manner, valuable lessons were learned. A deeper understanding of the day to day realities of dairy farming systems help researchers pinpoint management adaptations that are not only useful, but feasible, in light of improved seasonal climate forecasts. Furthermore, dairy farmers' perceptions regarding the use of seasonal climate information to mitigate the nitrate problem are critical for designing future dairy systems.

EFFECT OF NITROGEN AND PHOSPHORUS LEVEL AND SOWING DATE ON DYNAMIC CHANGE IN GRAIN FALLING NUMBER IN SPRING WHEAT IN GRAIN FILLING

Wheat grain falling number (GFN) is an important index that indicates the alpha_amylase activity and starch quality properties of wheat. The temporal dynamics of GFN and the effects of environmental conditions on GFN during grain filling have been scarcely reported systematically in the literature. In the present paper, field experiments were carried out in Harbin in 2002 to investigate temporal patterns in GFN, and how GFN was affected by N and P treatments and meteorological conditions during grain filling. Three genotypes of spring wheat with different qualities were used: a high protein_rich gluten genotype (`Wildcat'), a high protein_medium gluten genotype (`DN7742') and a low protein_poor gluten genotype (`NKH9'). The N and P applications included four treatments: 225 kg·hm~ -2 N, 450 kg·hm~ -2 P_2O_5 (F1); 300 kg·hm~ -2 N, 300 kg·hm~ -2 P_2O_5 (F2); 300 kg·hm~ -2 N, 450 kg·hm~ -2 P_2O_5 (F3) and 300 kg·hm~ -2 N, 600 kg·hm~ -2 P_2O_5 (F4). The results showed that temporal changes in GFN after anthesis could be fitted with a third_order convex curve (single peak curve), indicating that GFN rose in the initial stages and then fell during the middle and upper stages of grain filling. The effects of genotype and environmental factors on GFN formation were compared using this fitted curve. The temporal pattern in alpha_amylase activity fell to a greater extent during the initial stage and then rose weakly in the medium and upper stage. The results also indicated that from the 15th day after anthesis to maturity, with increasing nitrogen levels, medium phosphorus and high potassium levels (450 kg·hm~ -2 P_2O_5, 600-630 kg·hm~ -2 K_2O), GFN in the high protein_rich gluten genotype increased and the peak value rose but was delayed, and GFN decreased and the curve peak values fell but was ahead in both the high protein_medium gluten and low protein_poor gluten genotypes. GFN in the three genotypes all decreased with increasing phosphorus levels in the medium or low nitrogen treatments and at high potassium levels (300 kg·hm~ -2 N, 600-610 kg·hm~ -2 K_2O), and the curve differed among the three genotypes. The balance of nitrogen, phosphorus and potassium inputs was the key to forming higher GFN (lower alpha_amylase activity). Under conditions of moderate rainfall, the interaction of temperature and sunlight was the predominant influence on temporal formation patterns of GFN for different genotypes during grain filling, rainfall was the second, and PAR was the most sensitive among all the meteorological elements influencing the dynamic formation of GFN. Higher GFN was formed in all genotypes under conditions of high sunlight and high temperatures. Under conditions of high sunlight and temperature, the GFN in the high protein_rich gluten genotype increased with increasing PAR. The effects of meteorological conditions as well as differences among genotypes on GFN could be modeled by curve changes in the third_order equation. The variation of GFN in different genotypes under different environmental conditions (nitrogen and phosphorus fertilization and meteorological conditions) had significant affects on GFN.

Effects of Nitrogen Levels and Nitrate/Ammonium Ratios on Oxalate Concentrations of Different Forms in Edible Parts of Spinach

ABSTRACT Two hydroponic experiments were carried out to investigate the effects of nitrogen (N) levels and forms on the oxalate concentrations of different form in edible parts of spinach. Nitrogen was supplied at five levels (4, 8, 12, 16, 20 mM) in Experiment 1 and five ratios of nitrate (NO3 −) to ammonium (NH4 +) (100/0, 75/25, 50/50, 25/75, 0/100) at a total N of 8 mM in Experiment 2. Biomass of spinach increased markedly from 4 mM to 8 mM N and reached the flat with further increase in N. The total oxalate and soluble oxalate in leaves and shoots (edible parts) increased significantly with increasing N levels from 4 to 12 mM, while the total oxalate and insoluble oxalate decreased markedly when N level was further increased from 12 to 20 mM. Oxalates of different forms in petioles increased first and then decreased and elevated again with increasing nitrogen levels. In the second experiment, decreasing NO3 −/NH4 + ratios markedly increased at first and then significantly decreased the biomass of spinach plants and the maximum biomass was recorded in the treatment of the NO3 −/NH4 + ratio of 50:50. The oxalate concentrations of different form in leaves and shoots were all decreased obviously as the ratio of NO3 −/NH4 + decreased from 100:0 to 0:100. Concentrations of total oxalate and soluble oxalate in petioles could be reduced by increasing ammonium proportion and were the lowest as the ratio of NO3 −/NH4 + was 50:50 and insoluble oxalate decreased as nitrate/ammonium ratio decreased. The concentrations of oxalate forms in leaves were all higher than those in petioles and soluble oxalate was predominant form of oxalates in both trials. It is evident that high biomass of spinach can be achieved and oxalate concentrations of different forms can be reduced by modulating N levels and NO3 −/NH4 + ratio, so this will benefit for human health especially for those people with a history of calcium oxalate kidney stones.