Low Nitrogen Levels Research Articles

Low-Level Nitrogen and Short-Term Addition Increase Soil Carbon Sequestration in Chinese Forest Ecosystems

Low-Level Nitrogen and Short-Term Addition Increase Soil Carbon Sequestration in Chinese Forest Ecosystems

Effect of Integrated Use of Coffee Husk Compost and NPS Fertilizer on Soil Physicochemical Properties and Yield of Coffee (<i>Coffea arabica L</i>.) at Haru, Ethiopia

Integrated application of inorganic and organic fertilizers is the main sources for replenishing plant nutrients in agricultural soils. However, selecting the optimum combination of these resources based on soil type and crop species is necessary. In this context, field experiment was conducted at Haru research center to assess the effect of coffee husk Compost and NPS Fertilizer on soil physicochemical properties and Yield of coffee in 2018/2019. The treatments were the different rates of both compost and NPS fertilizers laid out in randomized complete block design. The results of the study showed that combined application of coffee husk compost and NPS fertilizers were improved soil moisture and total porosity over control, while, bulk density was decreased below the control. Combined application of coffee husk compost at (7.5 t ha^-1) and mineral NPS fertilizer at (50 kg ha^-1) has better improved yield of coffee crop. The experimental yield of Manasibu variety for present study from the station was 1.59 t ha^-1. Therefore, based on the result of the study it can be concluded that under condition of low soil pH of study area the availability of essential nutrients (e.g. P, N, K, Ca, Mg, and Mo) are critically affected. This indicates that the strong acid pH values at Haru Research sub-center require more attention. Moreover, the low levels of CEC, organic carbon, total nitrogen, and available P contents at study area soils confirm that soil fertility is among the constraints for sustainable coffee production in the Haru district. In response to this application of integrated NPS fertilizer and coffee husk compost with different rates improved soil physicochemical properties and coffee yield. The study recommended that the use of 7.5 t ha^-1 coffee husk compost and 50 kg ha^-1 of NPS fertilizer can be the best alternative integrated soil fertility management option in place of the sole application of inorganic fertilizers at study area tentatively. Nevertheless, in order to give conclusive recommendation further research studies are needed for more soil types and coffee crop varieties.

Status of Selected Physicochemical Properties of Soils Under Long Term Sugarcane Cultivation Fields at Wonji-Shoa Sugar Estate

A declining trend in per hectare yield of sugarcane in Wonji-Shoa Sugar Estate is being observed due to altering of soil physicochemical properties resulted from long term sugarcane cultivation. Cognizant of this fact, a study was conducted in 2017at Wonji-Shoa Sugar Estate with the objective of determining the effects of more than 62 years of sugarcane cultivation on the physicochemical properties of soil. In order to achieve this objective disturbed and undisturbed soil samples were collected from 0-30 and 30-60 cm layers of selected cultivated and uncultivated light and heavy soils for laboratory analysis. Results of the study indicated that long term cultivation of sugarcane at the same depth and low soil organic matter content of cultivated fields induced soil compaction and consequently highest bulk density was recorded in subsoil layer of cultivated than uncultivated land. The bulk density and total porosity values were out of ranges recommended for optimum sugarcane cultivation and suggest the existence of some degree of compaction. The finding further showed that the pH of study area soils is out of the normal pH range for sugarcane plant growth. The soil organic carbon, total nitrogen content and available phosphorus concentration of soils under both land uses of all soils was found within low range. Therefore, based on the result of the study it can be concluded that under condition of strong base soil pH of study area the availability of essential nutrients are critically affected. This indicates that the strong pH values at Wonji-Shoa Estate require more attention. Moreover, the low levels of organic carbon, total nitrogen, and available P contents under both cultivated and uncultivated soils indicated that soil fertility is among the constraints for sustainable sugarcane production in the estate. Based on the findings and conclusions of this study one can recommend that to maintain sustainability of sugarcane production in the estate soil management practices that can protect as well as ameliorate soil compaction, increase soil organic carbon, total nitrogen, soil available P and that can decrease soil pH are important. Nevertheless, in order to give conclusive recommendation further research studies are needed for more soil management units in the estate.

Protective Effect of Yerba Mate on Rats Fed on High Cholesterol Diet- An Experimental Study

Introduction: Yerba mate tea, a concoction made from the leaf extracts of the tree Ilex paraguariensis, is a broadly consumed non alcoholic beverage in Latin America which is gaining rapid introduction into the world market. Aim: To explore the influence of Yerba Mate (Ilex paraguariensis) powder and beverage on induced hypercholesterolemic rats. Materials and Methods: The experiment was carried out for a duration of one year from February 2020 to January 2021 at University of Ha’il, Ha’il, Saudi Arabia, on 48 male Albino rats divided into six subgroups; Control (-) group: group fed a basal diet. Rats in the other five groups fed on basal diet containing 2% cholesterol+0.25% bile salts for two weeks to induce hypercholesterolemia. Then those rats were subdivided into: control(+)group:groupthatremainedhypercholesterolemic.Yerba Mate Powdered (YMP) 15% group: fed on hypercholesterolemic diet+YMP15%; YMP 10% Group: fed on hypercholesterolemic diet+YMP10%; Yerba Mate Beverage (YMB) 15% group: fed on a hypercholesterolemic diet+YMB 15%; and YMB 10% group: fed on a hypercholesterolemic diet+YMB 10%. Results: It was found that, with increasing the amount of Yerba Mate powder or beverage, the total cholesterol, triglycerides, Low Density Lipoprotein-Cholesterol (LDL-C), Aspartate Transaminase (ALT), Alanine Transaminase (ALT), urea nitrogen and glucose levels decreased significantly (p<0.05) and the best result belonged to the group of rats that fed on Yerba Mate 15% powder. Conclusion: It can be concluded that, supplementation with high percentage of Yerba Mate powder (15%) exerts a positive impact on the lipid profile and other biochemical parameters in hypercholesterolemic rats.

Effect of Supplementing Rice Straw with Pigeon Pea Forage on Rumen and Blood Metabolites of Yankasa Sheep

A study was conducted to determine the effect of supplementing rice straw with pigeon pea forage on rumen and blood metabolites of Yankasa sheep. Sixteen yearling Yankasa ewes were used for the study. A completely randomized design was used with four animals per treatment. A basal rice straw diet was provided ad libitum and pigeon pea forage supplemented at 0.5, 1.0 and 1.5%of the body weight. Rumen and blood samples were collected at 3, 6, 9, 12 and 24 hours post-feeding. Results of the study showed low (1.16-3.81mg/100ml) NH3-N concentration in the unsupplemented ewes. Supplementation at 1 % body weight improved the level of NH3-N concentration to 10.38mg/100ml. Volatile faty acids also increased from 26.33 to 43.33mg/l in 0.0% and 1.0% of body weight pigeon pea forage supplementation. pH variations within treatments remain within acceptable range for rumen microbial activity: There was a uniformly low level of plasma urea nitrogen in the unsupplemented diet across sampling time, supplementing at 1.0% of the body weight had the highest plasma urea nitrogen level with 3 and 6 hours post-feeding being significantly (P<0.05) higher than other sampling time. Levels of packed cell volume and haemoglobin improved from 21.00% and 48% in the supplemented diet to 32.00% and 73% at 1.0% pigeon pea forage supplementation respectively

Maize Response to Sole and Combined Effects of Nitrogen and Nematode Stresses

Crops grown on the field or in phytotrons are faced with different biotic stresses including plant-parasitic nematodes (PPNs) and abiotic stresses such as drought and poor soil fertility (low nitrogen levels). In this study, the interactive responses of a low-nitrogen tolerant variety LNTP-YC6 and a regular variety BR-9928-DMRSR to Pratylenchus zeae under four nitrogen-levels: no amendment; [T0], low nitrogen [100kgN/ha NPK; T1], optimum nitrogen [200kgN/ha NPK + Urea; T2] and compost [10t/ha; T3] were investigated. The treatments were arranged in a 2 x 4 factorial fitted into randomised complete block design (RCBD) with four replicates. Data were collected on growth parameters (plant height and stem girth), yield components (number and weight of cobs), lesion score (LS), final nematode population (FNP) and reproductive factor (RF). Low nutrient stress in combination with nematode infection generally reduced maize growth and yield. Growth parameters of BR-9928-DMRSR variety were generally high while yield parameters of LNTP-YC6 variety were significantly greater than in BR-9928-DMRSR variety. However, T2 and T3 improved growth and yield of both maize varieties compared to T0, with T2 being superior to T3. Meanwhile, T3 reduced FNP more than T2. FNP (107.65) and RF (1.3) of P. zeae on LNTP-YC6 variety and with T3 was significantly low compared to T2 (178, 3.34), T0 (188, 3.6) and T1 (217, 5.0). In all the parameters considered, LNTP-YC6 outperformed BR-9928-DMRSR variety. In conclusion, soil amendment with optimum rate of nitrogen and compost reduced nematode population and enhanced maize growth, while low nitrogen in combination with nematode stress reduced maize yield.

Two galling insects (Hartigiola annulipes and Mikiola fagi), one host plant (Fagus sylvatica) – differences between leaf and gall chemical composition

Gall-inducing organisms change the chemical properties of galled organs and host plants due to the development of gall tissues that are supposed to shelter the galler and provide it with nutrients. Hartigiola annulipes and Mikiola fagi represent the gall midge family (Diptera; Cecidomyiidae). They share a host plant species, the common beech (Fagus sylvatica), whose leaves they use for galling. Their galls are single-chambered and occur on the upper side of the leaf blade. The morphologies of their galls are different, but there is a lack of studies comparing the impact of both species on the common host. Therefore, we analysed the total contents of carbon, nitrogen, soluble carbohydrates, starch, soluble phenolics and tannins in galls, galled leaves with removed galls and leaves without galls. Samples were collected in two different forest stands in western Poland (Scots pine forest with artificially planted beech trees and a natural beech forest). The influence of the studied gallers on the leaves is species- and forest-dependent. Perhaps seasonal changes and the level of infestation are also responsible for the chemical changes. The content of soluble carbohydrates in the galls of H. annulipes reaches an optimized level and is independent on the forest type. A high infestation level by H. annulipes is manifested itself in an elevated content of total soluble phenolics and tannins in leaves, while gall tissues do not accumulate soluble phenolics. The low levels of nitrogen in the gall tissues of both gallers leads to the rejection of the nutrition hypothesis; however, M. fagi galls act as sinks for soluble carbohydrates.
 Keywords: plant galls, chemistry, gall midge, common beech, biochemistry

Two galling insects (Hartigiola annulipes and Mikiola fagi), one host plant (Fagus sylvatica) – differences between leaf and gall chemical composition

Gall-inducing organisms change the chemical properties of galled organs and host plants due to the development of gall tissues that are supposed to shelter the galler and provide it with nutrients. Hartigiola annulipes and Mikiola fagi represent the gall midge family (Diptera; Cecidomyiidae). They share a host plant species, the common beech (Fagus sylvatica), whose leaves they use for galling. Their galls are single-chambered and occur on the upper side of the leaf blade. The morphologies of their galls are different, but there are a lack of studies comparing the impact of both species on the common host. Thus, this was the aim of this study. We analysed the total contents of carbon, nitrogen, soluble carbohydrates, starch, soluble phenolics and tannins in galls, galled leaves with removed galls and leaves without galls collected in two different forest stands in western Poland (a Scots pine forest with artificially-planted beech trees and a natural beech forest). The influence of the studied gallers on the leaves is species- and forest-dependent. Perhaps seasonal changes and the level of infestation are also responsible for the chemical changes. The content of soluble carbohydrates in the galls of H. annulipes reaches an optimized level and is independent of the forest type. A high infestation level by H. annulipes is manifested itself in an elevated content of total soluble phenolics and tannins in leaves, while gall tissues do not accumulate soluble phenolics. The low levels of nitrogen in the gall tissues of both gallers leads to the rejection of the nutrition hypothesis; however, M. fagi galls act as sinks for soluble carbohydrates.

Correlation and Path Coefficient Analysis of Yield Attributes in Grain Sorghum (Sorghum bicolor L.) Genotypes

Path coefficient was computed to estimate the contribution of individual traits to yield in grain sorghum .An investigation was carried out with 24 restorer lines of sorghum and one check variety Doradoto asses association of grain yield components and their direct and indirect effects on grain yield/plant during 2019 and 2020 growing seasons at Shandweel Agric. Res. Station, Egypt under four levels of nitrogen fertilization (60, 80 .100 .120 kg N / fed). Results of combined analysis of variance showed that significant or highly significant variations were recorded for environments, genotypes, and their location for various studied morphological and yield traits. The results of correlation analysis indicated that 1000-grain weight, panicle length, panicle width and plant height positive and significant correlation with grain yield. Plant height had maximum positive direct effect on grain yield/plant followed by 1000-grain weight. The best genotype was Rsh-19 for grain yield / plant , Rsh-22 for 1000-grain weight , Adv-44 for panicle width , Rsh-20 for panicle length , Sel pop- 13 for earliness and Rsh-12 for plant height . The highest mean values for all traits except days to 50% flowering were obtained under high nitrogen level (120 Kg N/fed) in both two seasons while the reverse was obtained under low nitrogen level (60 Kg N/ fed) in both two growing seasons.

A comparative assessment of growth, pigment and enhanced lipid production by two toxic freshwater cyanobacteria Anabaena circinalis FSS 124 and Cylindrospermopsis raciborskii FSS 127 under various combinations of nitrogen and phosphorous inputs.

Nitrogen and phosphorous are important nutritional regulators for the growth of cyanobacteria, thereby having a significant impact in bloom formation by toxic species. Usage of toxic cyanobacteria for increasing valuable metabolite production by nutrient manipulation is still unexplored. Hence, the current work is aimed to estimate and compare growth, pigment, and increased lipid production coupled with the identification of fatty acids between two toxic strains-Anabaena circinalis FSS 124 and Cylindrospermopsis raciborskii FSS 127 under various combinations of these two nutrients. Low level of nitrogen and phosphorous enhanced lipid content in both strains (˃ 20% and 30% respectively) and C. raciborskii, respectively. Lipid productivity in low phosphorous concentration (P0.5) was achieved significantly high in C. raciborskii. Similarly, a substantial amount of carotenoids was obtained at reduced nitrogen and phosphorous in C. raciborskii accompanied by lessened growth and Chl a concentration. Unlikely, enough biomass (˃ 2 g L-1) was produced at high nutrient levels in both species. Comparative statistical significance (p < 0.05) was found between two species regarding biomass production, chlorophyll concentration, lipid content, and productivity and between these factors in each species under both nutrient variations. FAME of Cylindrospermopsis is composed of saturated fatty acids (˃ 50%) and MUFA (˃ 25%) while Anabaena contains PUFA (˃ 21%) additionally. However, the study highlights C. raciborskii as potential lipid and carotenoid producer at nutrient stress and finds a novel way to utilize these cyanobacterial biomasses, which cause immense environmental hazards and life threats.

Concomitant emphysema might increase the false-negative rate of urinary antigen tests in patients with pneumococcal pneumonia: results from a retrospective study.

The urinary antigen test (UAT) is a rapid diagnostic method for pneumococcal pneumonia, but the high false-negative rate of 30% may affect its reliability. To maximize the utility of UAT, it is necessary to investigate the patient factors affecting UAT results. However, there is no report elucidating the association between its utility and pre-existing lung abnormalities. We retrospectively reviewed 388 patients with pneumococcal pneumonia confirmed by blood and/or sputum culture tests. Finally, 94 of 388 patients who had the results of UAT and computed tomography scans were enrolled to evaluate the association between the utility of UAT and patient factors including pulmonary emphysema and fibrosis. The overall positive rate of UAT was 69.1%. The positive rates of UAT in the patients with emphysema were significantly lower than those in individuals without emphysema (33.3% and 77.6%, p < 0.001). Univariate logistic regression analysis showed that the presence of emphysema was associated with a low positive rate (odds ratio 6.944, 95% confidence interval 2.268-21.231). Multivariate logistic analysis showed that the presence of emphysema and lower levels of serum blood urea nitrogen (BUN) were significantly and independently associated with a low positive rate. The combination of emphysema and BUN can potentially stratify the positive rate of UAT in patients with pneumococcal pneumonia. Patients with pneumococcal pneumonia and emphysema have a lower positive rate of UAT. Additionally, the combination of emphysema and serum BUN value may be useful to evaluate the reliability of the negative results of pneumococcal UAT.

The Influence of Three Years of Supplemental Nitrogen on Above- and Belowground Biomass Partitioning in a Decade-Old Miscanthus × giganteus in the Lower Silesian Voivodeship (Poland)

Because of the different opinions regarding nitrogen (N) requirements for Miscanthus × giganteus biomass production, we conducted an experiment with a set dose of nitrogen. The objective of this study was to examine the effects of nitrogen fertilization on the biomass yield, water content, and morphological features of rhizomes and aboveground plant parts in various terms during a growing season over the course of three years (2014–2016) in Lower Silesia (Wroclaw, Poland). The nitrogen fertilization (dose 60 kg/ha and control) significantly affected the number of shoots (p = 0.0018), the water concentration of rhizomes (p = 0.0004) and stems (p = 0.0218), the dry matter yield of leaves (p = 0.0000), and the nitrogen uptake (p = 0.0000). Nitrogen fertilization significantly affected the nitrogen uptake in all plant parts (p = 0.0000). Although low levels of nitrogen appeared to be important in maintaining the maximum growth potentials of mature Miscanthus × giganteus, the small reductions in the above- and belowground biomass production are unlikely to outweigh the environmental costs of applying nitrogen. More studies should use the protocols for the above- and belowground yield determination described in this paper in order to create site- and year-specific fertilizer regimes that are optimized for quality and yield for autumn (green) and spring (delayed) harvests.

Evaluation on morpho-physiological characters of synthetic maize genotypes on low soil nitrogen level condition

A study aimed to evaluate the growth and production of several synthetic maize lines at low nitrogen level was conducted at the Indonesian Cereals Research Institute Experimental Farm in Bajeng District, Gowa Regency, South Sulawesi. The research was carried out from September to December 2018. The study also aimed to determine the nitrogen dose that could be used for selection of synthetic maize genotypes against low nitrogen doses. The study was conducted in the form of an experiment using a Split Plot Design. Five levels of Nitrogen fertilizer were used namely 0, 50, 100, 150, and 200 kg N per hectare. Various genotypes treatment were consisted of 4 synthetic maize genotypes namely Syn 5, Syn 6, Syn 7, Syn 8 and 2 comparative varieties namely Bisma and Lamuru. The results show a significant interaction between the treatment of nitrogen doses and the synthetic maize genotype on the morphological and physiological characters of the maize genotypes. Genotypes gave the best results at nitrogen doses of 100 kg N ha−1 was Syn8 (8.67 tons ha−1) and 50 kg N ha−1 (6.47 tons ha−1). Nitrogen doses of 50 kg N ha−1 and 100 kg N ha−1 can be used for the selection of maize tolerant to low nitrogen condition with productivity of 4.57 tons ha−1 and 8.67 tons ha−1, respectively. There is potential for the Syn8 genotype to be developed for low-nitrogen-tolerant maize varieties due to higher production compared to the comparative variety.

Analysis of main factors affecting silage fermentation of sorghum prepared with whole crop and stover in semiarid West Africa

Sorghum (Sorghum bicolor L.) is widely cultivated in semiarid West Africa as a combined crop for human consumption and animal feed. In order to address the shortage of ruminant feed in Burkina Faso, we studied the potential of preparing silage from sorghum at various growth stages and analysed the main factors affecting silage fermentation, including the microbial population, chemical composition and ensiling characteristics of sorghum prepared with and without microbial additives at three stages of development (soft dough; hard dough; physiological mature stover). After 90 d of ensiling, lactic acid bacteria (LAB) became the dominant microorganisms in silages. The silage from soft dough sorghum exhibited the highest LAB counts, water-soluble carbohydrate (WSC) and crude protein content. In addition, silage presented greater quality with higher (p < 0.05) lactic acid content and lower (p < 0.05) pH and ammonia nitrogen levels than those at hard dough stage and stover. The WSC and LAB were the important factors affecting silage fermentation and the addition of LAB and cellulase improved fermentation quality. The combined additives displayed a synergistic effect and when silage is prepared with sorghum at soft dough stage, it has best potential for controlling spoilage microorganisms and preserving the silage quality for animal feed.

Maternal inheritance in the efficiency of use of Azospirillum brasilense in maize

The maize crop demands high nitrogen input. However, Brazilian soils are generally deficient in this element. The use of associative bacteria, such as Azospirillum brasilense , can benefit agricultural systems that use low nitrogen levels. This study analyzes the occurrence of maternal inheritance in traits of maize genotypes for the efficiency of response to Azospirillum brasilense . For that, we used 132 treatments consisting of 66 crosses in complete diallel scheme with reciprocals. We evaluated two experiments in the same area and under the same conditions. We performed one experiment without nitrogen topdressing / with Azospirillum brasilense inoculation and another with nitrogen topdressing / without Azospirillum brasilense inoculation. These experiments took place in the second crop of 2017, in a randomized block design with two replicates. After obtaining the data, we estimated the efficien­cies for the use of Azospirillum brasilense by adapting the Fischer model. From these data, we conducted analy­sis of variance, t test, and diallel analysis, thus estimating maternal inheritance. The evaluated traits showed no maternal inheritance, being governed by nuclear genes. Most genotypes were efficient for the use of A. brasilense , for all traits.

Centennial glacier retreat increases sedimentation and eutrophication in Subantarctic periglacial lakes: A study case of Lake Uruguay

High resolution XRF scanning documented inter-annual paleolimnological changes of a Subantarctic periglacial lake, during a process of centennial glacier retreat in King George Island, Antarctica. Two major paleoenvironmental stages were inferred from the combined analysis of elemental, molecular and isotopic biomarkers, with a boundary or transition set at about 3200 yr BP. The first stage was characterized by a relatively low allochthonous organic content, reduced productivity and nitrogen levels. Such paleoenvironmental conditions are interpreted as a terrestrial system under periglacial influence, where material influx was related to erosion process from the melt water discharge, because of the proximity to the Collins Glacier ice cap. After the major Holocene glacier advance dated at about 3500 yr BP, the ice cap retreat led to the formation of Lake Uruguay, which involved in filling processes leading to moraine deposits, proglacial meltwater channels, and lakes next to the land glacier. During the second stage, with the onset of the Current Warm Period, prior to 1900 CE the stabilization of the Zr/Rb ratio within the laminated sediments documented the origin of the lacustrine sedimentation system, with subsequent increases in the sedimentation rate and biomass content (total nitrogen and organic carbon). Time series analyses revealed that the lake displayed variability cycles related to El Niño Southern Oscillation (ENSO), as reflected by high resolution sedimentological proxies for grain size, weathering, allochthonous inputs from the watershed, increase of biomass and productivity, and changes in redox conditions, all of which displayed similar oscillation cycles from 2 to 6 yr. During this periglacial recession and associated eutrophication process, we detected a striking loss in both bacterial specific richness and diversity as inferred from preliminary selected ancient DNA analyses. Thus, the Antarctic warming scenario leading to glacier depletion appears to exert deterioration consequences on the Subantarctic microbial web.

Low-Cost Multispectral Sensor Array for Determining Leaf Nitrogen Status

A crop’s health can be determined by its leaf nutrient status; more precisely, leaf nitrogen (N) level, is a critical indicator that carries a lot of worthwhile nutrient information for classifying the plant’s health. However, the existing non-invasive techniques are expensive and bulky. The aim of this study is to develop a low-cost, quick-read multi-spectral sensor array to predict N level in leaves non-invasively. The proposed sensor module has been developed using two reflectance-based multi-spectral sensors (visible and near-infrared (NIR)). In addition, the proposed device can capture the reflectance data at 12 different wavelengths (six for each sensor). We conducted the experiment on canola leaves in a controlled greenhouse environment as well as in the field. In the greenhouse experiment, spectral data were collected from 87 leaves of 24 canola plants, subjected to varying levels of N fertilization. Later, 42 canola cultivars were subjected to low and high nitrogen levels in the field experiment. The k-nearest neighbors (KNN) algorithm was employed to model the reflectance data. The trained model shows an average accuracy of 88.4% on the test set for the greenhouse experiment and 79.2% for the field experiment. Overall, the result concludes that the proposed cost-effective sensing system can be viable in determining leaf nitrogen status.

Physico-chemical analysis of selected agricultural soil samples in Junnar tehsil of Pune district, Maharashtra

An experiment was undertaken at College of Agriculture Business Management, Narayangaon Maharashtra to investigate the physico- chemical properties of Onion and Tomato soil at ten different sites of Junnar tehsil of Pune District during February 2018 to May 2019. The soil parameters like soil pH, EC, Organic Carbon, Nitrogen, Potassium and Phosphorous content were analyzed. It was found that there was a marked variation in nutrients and parameters of various sample point in different farmers field. The results of the study show the low levels of Nitrogen, Phosphorous and Potassium in both sites. Also the organic matter is low during the study area.

Effects of carbohydrate sources on a biofloc nursery system for whiteleg shrimp (Litopenaeus vannamei)

In biofloc technology carbohydrate is added to stimulate the biofloc growth, the latter helps to improve water quality, reduce the need for water exchange and may serve as natural shrimp feed. The large diversity among possible carbohydrate sources makes the selection of a suitable carbohydrate difficult. This study investigated how corn starch addition compared to molasses addition affected water quality, biofloc and periphyton proximate composition, shrimp production parameters, diurnal fluctuations and distribution of carbon and nitrogen in whiteleg shrimp (Litopenaeus vannamei) culture system. The results showed that both corn starch and molasses addition treatments resulted in low ammonium nitrogen levels in the water. The total suspended solids and volatile suspended solids in both treatments increased over time and were not significantly different among treatments. The protein content in the dry matter of the biofloc varied from 34% to 48%, being higher in the molasses treatment. The same was observed for the protein content in the dry matter of the periphyton which ranged between 16% and 26%. The corn starch treatment resulted in significantly higher shrimp growth rate, production, average body weight, and lower FCR compared to molasses addition. Water quality was stable on a daily basis, but changed over the weeks. Carbon and nitrogen accumulations in the system were not significantly different among treatments.

Effect of Sowing Dates and Nitrogen Levels on Popula-tion of Okra Jassids (Amrasca biguttula biguttula Ishida)

Okra (Abelmoschus esculentus L. (Moench) is one of the most important vegetable crops grown in Nepal. The crop is susceptible to various insect pests of which jassids (Amrasca biguttula biguttula Ishida.) is most predominant which reduces production and deteriorates seed quality of okra. A field study was conducted at Horticulture Farm, Agriculture and Forestry University, Rampur, Chitwan, Nepal to elucidate the effect of sowing date and nitrogen levels on the population and damage of jassids from April to September 2018. Three levels of nitrogen (100, 200 and 300 kg N ha-1) and five sowing dates (8th April, 20th April, 2nd May, 14th May and 26th May, 2018) were evaluated in randomized complete block design with three replications. Results indicated that the highest damage score was recorded in okra which was sown on 8th April (2.39) followed by 20th April (2.31) and 2nd May (1.26). The highest damage score of jassids was obtained with the use of nitrogen at the rate of 200 kg ha-1 (1.94) followed by 300 kg/ha (1.72) and 100 kg ha-1 (1.54). Mean population of jassids was maximum with okra sown on 20th April (29.91) and minimum with okra sown on 26th May (6.95). This study showed that late planting i.e. 26th May and applying low level of nitrogen i.e. 100 kg N ha- 1is an effective approach for reducing the jassids population and its damage in okra.