Plant Tissue Nitrogen Research Articles

Primary nutrient content and its uptake in finger millet (Eleusine coracana) as influenced by different nutrient management and seed priming

A field experiment was conducted in the experimental plots of DKS farm, IGKV, Bhatapara Dist- Baloda Bazaar, Chhattisgarh during kharif season of the year 2019. The soil of the experimental field was Alfisol and climate was sub-humid with a total rainfall of 872.2 mm during the crop growth. The objectives of experiment were to the study the effect of various nutrient management and seed priming treatments on N, P and K content and uptake of finger millet. The experiment was laid out in split-plot design. The treatments constituted with five nutrient management N1 (control), N2 (125 kg Neem cake + 1.25 tons ha-1 vermicompost), N3 (50“Kg/ha N : 50 Kg/ha P2O5 : 50 Kg /ha K2O”and 2% Borax spray at flowering), N4 (125 Kg Neem cake + 1.25 tons ha-1 vermicompost + 50 Kg/ha N : 50 Kg/ha P2O5 : 50 Kg /ha K2O and 2% Borax spray at flowering) and N5 (Recommended dose of fertilizer i.e. 20 Kg/ha N”: 20 Kg/ha P2O5 : 10 Kg /ha K2O) in main plots with four priming treatment P1 (control), P2 (Hydro priming for 6 hrs), P3 (Seed priming with 2% KH2PO4 for 6 hrs) and P4 (Seed priming with 20% liquid Pseudomonas fluorescens) in sub plots. Results revealed that the nitrogen, phosphorus, and potassium contents in plant tissue were not affected significantly by nutrient management and seed priming treatments. However, the nutrient uptake of nitrogen, phosphorus, and potassium were found in higher range where either higher doses of chemical fertilizers or the chemical fertilizers in combination with organic manures were applied. No significant effect of seed priming was seen for nutrient uptake of these elements by plants.

Fragrant rice performances in response to continuous zero-tillage in machine-transplanted double-cropped rice system

Zero-tillage is one of conservation tillage techniques. In order to investigate the effects of continuous zero-tillage on yield formation and grain 2-acetyl-1-pyrroline (2-AP, key component of fragrant rice aroma) content of fragrant rice, present study was conducted with a six-season field experiment from 2017 to 2019. The conventional tillage (twice puddling with rotary cultivator before transplanting) was set as control (CK) and zero-tillage was set as treatment (ZT). At the first year after applying zero-tillage, yield loss was observed in the ZT treatment which was attributed to the lower effective panicle number per area and grain number per panicle. However, from late season in 2018 to late season in 2019, significant higher grain yield was recorded in ZT than CK. ZT increased the net photosynthetic rate and chlorophyll content (SPAD value) by 6.81–20.77% and 7.23–23.80% in the last three cropping seasons compared with CK. Higher nitrogen, potassium and phosphorus accumulations in plant tissues were also recorded in ZT than CK from late season in 2018 to late season in 2019. Other hand, higher grain 2-AP content was recorded in ZT than CT in the whole six cropping seasons which might be related to the grain proline content. Furthermore, compared with CK, ZT significantly increased the soil organic matter content and the number of bacteria, fungi and actinomycetes in the last three cropping seasons. In conclusion, continuous zero-tillage could improve soil and increase the photosynthesis and nutrient accumulation and finally achieve the improvement of fragrant rice yield.

A low-cost smartphone controlled sensor based on image analysis for estimating whole-plant tissue nitrogen (N) content in floriculture crops

Monitoring and maintaining plant tissue nitrogen (N) content in the optimal range is crucial for proper growth and quality of floriculture crops. Direct laboratory measurements of tissue N content is destructive, time-consuming and expensive. The equipment costs for indirect measurement of tissue N content are high. Currently, there are no low-cost, reliable and non-destructive techniques for measuring whole-plant tissue N content in floriculture crops. The objective of this study is to develop a low-cost sensor that can instantaneously and non-destructively estimate whole-plant tissue N content in floriculture crops. The technique involves a sensor, smartphone and local computer. The low-cost sensor was built using Raspberry Pis, camera modules and light filters. A smartphone interacts with both the sensor and the local computer using wireless network connection. Using a web-interface, smartphone was connected to the sensor for capturing and transferring plant images to a cloud storage. Subsequently, the smartphone was remotely connected to the local computer with image-processing software. Images were processed to calculate a reflectance ratio (Rratio). Results indicated linear and positive relationships between the laboratory measured whole-plant N content and Rratio (r2 = 0.70) and chlorophyll concentration and Rratio (r2 = 0.71). Further, a model based on stepwise selection (N = 125) indicated that tissue N mostly affected Rratio (partial R2 = 0.66), while other elements in the plant tissue had minimal effect on the ratio. Based on these results, the developed algorithm can be used to instantaneously compute whole-plant tissue N content using the low-cost sensor.

Plant responses to nutrient addition and predictive ability of vegetation N:P ratio in an austral fen

Abstract Previous studies of the N:P ratio in wetland plants have been carried out in northern hemisphere wetlands where atmospheric nitrogen deposition is higher. There is little research on foliar N:P ratio as a potential indicator of nutrient limitation in vegetation communities in southern hemisphere wetlands. This study aimed to redress this knowledge gap and answer the following questions: how well does the plant tissue nitrogen to phosphorus (N:P) ratio predict wetland plant community nutrient limitation, as indicated by vegetation standing stocks and below‐ground biomass, in southern hemisphere fens? Secondly, what are the impacts of realistic upper levels of farm nutrient run‐off on natural montane fen vegetation? Low (35 kg ha−1 year−1) and high (70 kg ha−1 year−1) levels of nitrate‐N or ammonium‐N with and without P (20 kg ha−1 year−1) were added to 81 vegetation plots over a period of 2.75 years. Species composition, plant nutrient status, and above‐ground live vegetation standing stocks were assessed after 3 years, and below‐ground biomass after 2 years. Plant tissue analysis suggested the community was N limited or N and P co‐limited; we found greater standing stocks of vegetation in plots treated with 70 kg ha−1 year−1 ammonium‐N, indicating N limitation. No difference between other treatments was found in above‐ground standing stocks or below‐ground biomass. Plant species cover increased in both high N treatments, consistent with N limitation. These changes in plant species cover were accompanied by significant decreases in species richness in both high N treatments. Native species dominated the vegetation and this was unaffected by nutrient addition (90% cover). This is one of the first studies to test and find support for the N:P ratio in southern hemisphere wetlands. Observed declines in species richness after N fertilisation in an N‐limited fen suggests increased N may pose risks to austral wetlands. Responses by plant communities (changes in composition, biomass) to lower levels of nutrient addition may require longer periods of fertilisation to be apparent in slow growing ecosystems.

Development of Bacillus safensis-based liquid bioformulation to augment growth, stevioside content, and nutrient uptake in Stevia rebaudiana.

The application of chemical fertilizers to enhance crop production is a major concern due to associated environmental pollution and health hazards. Hence, there is an urgent need to develop an eco-friendly solution to improve crop production and promote sustainable agriculture simultaneously. Stevia rebaudiana is an important medicinal crop being substitute for sugar, superior flavor outline, extensive medicinal properties, and also of agronomic interest. In the present study, bacterium STJP isolated from the rhizospheric soil of S. rebaudiana and identified as Bacillus safensis on the basis of 16S rRNA gene sequencing, showed good amount of zinc (4.4mg/L) and potassium (5.4mg/L) solubilization. Paneer-whey (a dairy waste) based bioformulation (P-WBF) was developed utilizing isolate B. safensis STJP (accession number NAIMCC TB-2833) and inspected for the quality and ability to enhance the growth, nutrients uptake, and stevioside content in S. rebaudiana. The application of P-WBF displayed a significantly higher concentration (153.12%) of stevioside in S. rebaudiana as compared to control. P-WBF treated Stevia plants showed significantly higher fresh and dry weight as well (as compared to control). Further, enhancement of phosphorous, nitrogen, potassium, and zinc uptake in plant tissue was also recorded by application of P-WBF. This study suggests the use of P-WBF based biofertilizer using B. safensis STJP to increase stevioside content in Stevia plant by a nutrient(s) linked mechanism. This novel approach can also be beneficial for utilization of a dairy waste in preparation of bioformulationand, for enhancement of crop yield by an ecofriendly manner leading to sustainable agriculture.

Efficiency of pumpkin (Cucurbita pepo), sweet wormwood (Artemisia annua) and amaranth (Amaranthus dubius) in removing nutrients from a smallscale recirculating aquaponic system

In aquaponic systems, plants absorb dissolved nutrients from aquaculture wastewater for their growth. The removal of nutrients allows reuse of water and minimises wastewater discharge to the surrounding environment. This study evaluated the relative nutrient removal efficiencies of three plant species and the performance of Nile tilapia (Oreochromis niloticus) in a small-scale aquaponic system. Three aquaponic systems were assigned as treatments PU (pumpkin), SW (sweet wormwood) and AM (amaranth). Physical-chemical water quality parameters were measured in the fish tanks as well as hydroponic inlets and outlets. Fish sampling was done every 2 weeks for 60 days. Results showed significantly (p < 0.05) lower nutrient concentrations in the hydroponic outlets than the inlets. There was no significant difference in nutrient removal efficiency of the plants (p > 0.05) for all the tested nutrients except for phosphorus. Phosphorus removal was substantially high in PU (75.5 ± 16.8%) than SW (47.36 ± 14.5%) and AM (40.72 ± 13.2%). In addition, the SW system had better (p < 0.05) relative growth rate (0.06 ± 0.00) than that of PU (0.05 ± 0.00) and AM (0.05 ± 0.00). Nitrogen and phosphorus content in plant tissues was significantly high (p < 0.05) in SW and PU plants respectively. Water quality parameters had a significant influence on the growth of fish (p < 0.05). The growth of fish was not different (p > 0.05) in the three treatments. The findings indicate that the tested plants can reduce nutrients in aquaculture discharge water.

Implications of nutrient enrichment for the conservation and management of seagrass Zostera muelleri meadows

Abstract Nutrient overenrichment in aquatic environments, or eutrophication, is increasingly affecting seagrass habitats around the world, leading to the degradation of seagrass ecosystems and the loss of associated ecosystem services. The resistance of seagrass to nutrient enrichment is believed to be site specific, yet the direct correlations between environmental factors and the resistance of seagrass meadows has not yet been adequately resolved. The response of seagrass beds to long‐term multiple‐level sediment nutrient enrichment represents a current research gap. This study therefore assessed the in situ long‐term influence of four levels of sediment urea fertilizer addition on Zostera muelleri plants using a manipulative experimental design at three sites with diverse sediment characteristics. Specifically, this study investigated the response of porewater nutrient concentration, seagrass morphology indices, and seagrass plant tissue carbon and nitrogen contents under experimental nutrient stress levels. Over a 13‐month experiment, sediment nutrient addition substantially increased the ammonium concentrations in the sediment porewater, significantly decreased seagrass morphology indices, and caused a carbon and nitrogen imbalance in plant tissues. Ammonium toxicity was more pronounced in seagrass meadows growing on sandy substrates with lower relative above‐ground biomass, which showed low resistance to eutrophication at sediment ammonium concentrations of up to 1 × 104 μM. Plants growing in muddy sand substrates with higher relative above‐ground biomass were more resistant to nutrient impacts, however, with a delayed negative response observed in response to higher nutrient concentrations (up to 1 × 105 μM). Our findings suggest that seagrasses in low‐nutrient sandy environments show more rapid responses to eutrophication, although seagrasses in both sandy and muddy substrates exhibited declines in response to a long‐term elevation of sediment nutrient concentrations. While continuing to assess the relative susceptibility of seagrass habitats across differing environments to inform coastal management, conservation efforts should allocate resources accordingly and prioritize reducing nutrient overenrichment in sensitive seagrass meadows.

Soil nematodes differ in association with native and non-native dune-building grass species

Non-native plant species can alter soil communities, which can lead to changes in their ecosystem functioning and facilitate invasive plant spread. In this study, we asked whether abundance, composition, or function of free-living soil nematode communities differed in association with two dune building grass species in US Pacific Northwest coastal dunes. In 2016, we surveyed soil nematode communities along foredune profiles at six sites in Oregon and Washington, USA, where the non-native beach grass Ammophila breviligulata co-occurred with the native dune grass Elymus mollis. We also measured plant-associated factors that might influence nematode communities, including plant tissue nitrogen, arbuscular mycorrhizal associations, litter production, and plant community diversity associated with the two grass species across the foredune profile. Elymus mollis plots had over twice as many nematodes on average as A. breviligulata plots and were also associated with a higher nematode enrichment index, especially on dune heels. This is possibly explained by higher percent leaf nitrogen content in E. mollis. Subtle differences in nematode community composition and plant tissue nitrogen between the two grass species indicate that A. breviligulata may be altering nutrient cycling across the dune profile, which could explain the arrested succession associated with this species on back dunes. However, overall, nematode communities shifted more in response to foredune cross-shore position and stabilization as opposed to changes in vegetation.

Limited effects of the maternal rearing environment on the behaviour and fitness of an insect herbivore and its natural enemy.

The maternal rearing environment can affect offspring fitness or phenotype indirectly via ‘maternal effects’ and can also influence a mother’s behaviour and fecundity directly. However, it remains uncertain how the effects of the maternal rearing environment cascade through multiple trophic levels, such as in plant-insect herbivore-natural enemy interactions. Pea aphids (Acyrthosiphon pisum) show differential fitness on host legume species, while generalist aphid parasitoids can show variable fitness on different host aphid species, suggesting that maternal effects could operate in a plant-aphid-parasitoid system. We tested whether the maternal rearing environment affected the behaviour and fitness of aphids by rearing aphids on two plant hosts that were either the same as or different from those experienced by the mothers. A similar approach was used to test the behaviour and fitness of parasitoid wasps in response to maternal rearing environment. Here, the host environment was manipulated at the plant or plant and aphid trophic levels for parasitoid wasps. We also quantified the quality of host plants for aphids and host aphids for parasitoid wasps. In choice tests, aphids and parasitoid wasps had no preference for the plant nor plant and aphid host environment on which they were reared. Aphid offspring experienced 50.8% higher intrinsic rates of population growth, 43.4% heavier offspring and lived 14.9% longer when feeding on bean plants compared to aphids feeding on pea plants, with little effect of the maternal rearing environment. Plant tissue nitrogen concentration varied by 21.3% in response to aphid mothers’ rearing environment, and these differences correlated with offspring fitness. Maternal effects in parasitoid wasps were only observed when both the plant and aphid host environment was changed: wasp offspring were heaviest by 10.9–73.5% when both they and their mothers developed in bean-reared pea aphids. Also, parasitoid wasp fecundity was highest by 38.4% when offspring were oviposited in the maternal rearing environment. These findings indicate that maternal effects have a relatively small contribution towards the outcome of plant-aphid-parasitoid interactions.

Organic amendment additions to rangelands: A meta-analysis of multiple ecosystem outcomes.

Interest in land application of organic amendments—such as biosolids, composts, and manures—is growing due to their potential to increase soil carbon and help mitigate climate change, as well as to support soil health and regenerative agriculture. While organic amendments are predominantly applied to croplands, their application is increasingly proposed on relatively arid rangelands that do not typically receive fertilizers or other inputs, creating unique concerns for outcomes such as native plant diversity and water quality. To maximize environmental benefits and minimize potential harms, we must understand how soil, water, and plant communities respond to particular amendments and site conditions. We conducted a global meta‐analysis of 92 studies in which organic amendments had been added to arid, semiarid, or Mediterranean rangelands. We found that organic amendments, on average, provide some environmental benefits (increased soil carbon, soil water holding capacity, aboveground net primary productivity, and plant tissue nitrogen; decreased runoff quantity), as well as some environmental harms (increased concentrations of soil lead, runoff nitrate, and runoff phosphorus; increased soil CO2 emissions). Published data were inadequate to fully assess impacts to native plant communities. In our models, adding higher amounts of amendment benefitted four outcomes and harmed two outcomes, whereas adding amendments with higher nitrogen concentrations benefitted two outcomes and harmed four outcomes. This suggests that trade‐offs among outcomes are inevitable; however, applying low‐N amendments was consistent with both maximizing benefits and minimizing harms. Short study time frames (median 1–2 years), limited geographic scope, and, for some outcomes, few published studies limit longer‐term inferences from these models. Nevertheless, they provide a starting point to develop site‐specific amendment application strategies aimed toward realizing the potential of this practice to contribute to climate change mitigation while minimizing negative impacts on other environmental goals.

Decomposer diversity increases biomass production and shifts aboveground-belowground biomass allocation of common wheat

Biodiversity is well known to enhance many ecosystem functions, but empirical evidence for the role of soil biodiversity for plant biomass production and allocation is scarce. Here we studied the effects of animal decomposer diversity (1, 2, and 4 species as well as a control without any decomposers) on the biomass production and aboveground-belowground biomass allocation of common wheat using two earthworm and two Collembola species using an additive design in two soil management types (organic and mineral fertilizer treatments) in a microcosm experiment. Shoot (+11%), spike (+7%), and root biomass (+56%), increased significantly with increasing decomposer diversity, and these effects were consistent across the two soil management types. Notably, decomposer diversity effects were stronger on root than on shoot biomass, significantly decreasing the shoot-to-root ratio (−27%). Increased plant biomass production was positively correlated with a decomposer richness-induced increase in soil water nitrate concentrations five weeks after the start of the experiment. However, elevated soil nitrate concentrations did not cause significantly higher plant tissue nitrogen concentrations and nitrogen amounts, suggesting that additional mechanisms might be at play. Consistent decomposer diversity effects across soil management types indicate that maintaining soil biodiversity is a robust and sustainable strategy to enhance crop yield.

Field evaluation of the fertilizing potential of biologically treated sanitation products

Among different approaches of treating source-separated urine and feces for agronomic utilization, the treatment by addition of nitrifying bio-seeds seems to be useful in increasing the fertilizing potential of these sanitation products by modifying and stabilizing the nitrogen profile. In this study, biological treatment was applied to an onsite resource-oriented sanitation system by adding nitrifying microorganism bio-seeds. Further, the potential of the sanitation products to be utilized as fertilizer for white radish (Raphanus sativus var. longipinnatus) cultivation was examined and compared with that of a commercial fertilizer. This was done through the measurement of nutrients released in soil samples as well as measurements of root mass, root length, and the measurement of accumulated nitrogen, sugar, and water content in plant tissues. Our results show that soil fertilized with a mixture of biologically treated urine and feces exhibits a statistically similar nutrient release trend to soil fertilized using a commercial fertilizer. Moreover, soil fertilized with a mixture of biologically treated urine and feces yielded larger white radishes with a higher sugar and water content, as well as a higher accumulation of nutrients in the plant tissues, than soil fertilized with a commercial fertilizer.

Effect of Phosphorus Levels on Soil Properties and Plant Tissues of Two Nerica Varieties

Phosphorus levels in the soil are easily fixed and rendered unavailable to plants even if they are found to be high and therefore, its influence on uptake of other nutrients such as nitrogen, and potassium cannot be overemphasized. In that view, an experiment was set out at KALRO-Mwea to investigate on the effect of phosphorus levels on soil properties and plant tissue nutrient contents of Nerica rice variety. The experiment was laid out in a Randomized Complete Block Design in split-split plot arrangement and replicated thrice. Two rice varieties (Nerica 11 and Nerica 4) formed the main plots and 4 phosphorus levels (0 kg P/ha, 25 kg P/ha, 50 kg P/ha and 75 kg P/ha) formed the sub plots. Highest net pH decreases of 0.20 and 0.22 units were recorded at 75 Kg haˉ¹ P2O5 in season 1 and season 2 respectively, while the lowest net decreases of 0.12 and 0.16 were elicited at 50 Kg haˉ¹ P2O5 treatment in season 1 and season 2 respectively. A net decrease was observed in all the CEC levels where phosphorus was applied in all the seasons in which the highest net decrease of 1.09 and 1.03 during season 1 and 2 respectively was elicited on the control treatment, while the lowest net decrease of 0.61 and 0.59 was elicited by the 50 Kg haˉ¹ P2O5 rate in season 1 and 2 respectively. There was an inverse relationship exhibited between the phosphorus level of applications and the soil phosphorus net decrease across the two seasons. The net decrease was highest at 0 Kg haˉ¹ P2O5 and increased significantly with increasing phosphorus rate. That content of soil nitrogen were low with a marginal increase recorded with application of phosphorus across the seasons. The highest net increase of 0.05% was observed at the 75 Kg haˉ¹ P2O5 rate and control in season 1 while the application rate of 50 Kg haˉ¹ P2O5 had the lowest net increase of 0.02% in season 2. Highest mean plant-tissue phosphorus of 62.05 ppm was recorded in Nerica 4 under 75 kg P/ha treatment. Highest plant tissue nitrogen of 0.686% and 0.713% for Nerica 4 and 11 respectively were elicited at 75 kg haˉ¹ P2O5 in season 1, whereas in season 2 the highest plant tissue nitrogen of 0.721% and 0.691% at 75 kg haˉ¹ P2O5 for Nerica 11 and 4 respectively was recorded. Application of phosphorous led to the highest plant-tissue phosphorus in both seasons indicating the importance of proper P fertilizer application where from this study 50-75 kg haˉ¹ P2O5 rate is recommended in rice growing.

Plant Nitrogen Status of Southern Highbush Blueberry (Vaccinium corymbosum L. Interspecific Hybrid) Grown in Pine Bark Amended Soils with Varying Rates of Nitrates

ABSTRACTAn experiment evaluating three fertilizer types (granular, liquid, and controlled released fertilizer) with nitrate ranging from 0% to 44% was conducted over two seasons on southern highbush blueberry ‘Star’ at the University of Georgia’s blueberry farm in Alapaha, GA. The objective was to identify the effect on fruit quality, plant growth, and plant tissue nitrogen status. This work demonstrated that the applications of fertilizer had similar effects on fruit quality and growth for ‘Star’ grown in sandy organic soils. In addition, fertilizers with 36.5% or 44% nitrate did not appear to have significant accumulation of nitrate in the leaves. Soil analysis revealed that none of the fertilized soils significantly increased cation exchange capacity; however, soil pH increased in soils with 36.5% and 44% nitrate applications. This suggests these nitrate levels will require continued soil monitoring and possible soil acidification to maintain appropriate soil pH for blueberry production (4.0–5.5 pH).

Carbon, nitrogen, and water stable isotopes in plant tissue and soils across a moisture gradient in Puerto Rico

AbstractStable isotopes in the water molecule (2H or D and 18O), carbon, and nitrogen are useful tracers and integrators of processes in plant ecohydrological systems across scales. Over the last few years, there has been growing interest in regional to continental scale synthesis of stable isotope data with a view to elucidating biogeochemical and ecohydrological patterns. Published datasets from the humid tropics, however, are limited. To be able to contribute to bridging the “data gap” in the humid tropics, here, we publish a relatively novel and unique suite of δ13C, δ15N, δ2H, and δ18O isotope data from three sites across a moisture gradient and contrasting land use in Puerto Rico. Plant tissue (xylem and leaf) samples from two species of mahogany (Swietenia macrophylla and Swietenia mahagoni) and soil samples down to 60 cm in the soil profile were collected in relatively “wet” (July 2012) and “dry” (February 2013) periods at two sites in northeastern (Luquillo) and southwestern (Susua) Puerto Rico. The same sampling suite is also being made available from a highly urbanized site in the capital San Juan. Leaf samples taken in July 2012 and February 2013 were analyzed for δ13C and δ15N; all xylem and bulk soil samples were analyzed for δ2H and δ18O. Soil samples taken in July 2012 were analyzed for δ13C and δ15N. Leaf δ15N and δ13C dataset showed patterns that are possibly associated with site differences. While spatial patterns were also apparent in soil δ15N and δ13C dataset, the positively linear δ15N –δ13C relationship tends to weaken with site moisture. Soil depth and site moisture patterns were also observed in the δ2H and δ18O datasets of bulk soil and xylem samples. The purpose of these datasets is to provide baseline information on soil–plant water (δ2H and δ18O, N = 319), δ13C (N = 272), and δ15N (N = 269) that may be useful in a wide range of research questions from ecohydrological relations to biogeochemical patterns in soils and vegetation.

White lupine yield under different sowing densities and row spacings

ABSTRACT The study aimed to evaluate different sowing densities and row spacings on grain yield and biomass in the white lupine crop, cv. ‘Comum’. The experimental design was a randomized block in a 4 x 4 factorial scheme, with four row spacings (20, 40, 60 and 80 cm) and four sowing densities in the row (10, 15, 20 and 25 plants m-1), with four replicates. The evaluated variables were: grain yield, hundred-grain weight, fresh and dry matter and the contents of nitrogen, phosphorus and potassium in the plant tissue. The highest grain yield was obtained with row spacing of 20 cm, regardless of plant density. The density of 25 plants m-1 and row spacing of 20 cm increased the fresh and dry matter yield. The adjustment of plant density and row spacing did not affect the content of nitrogen, phosphorus and potassium in plant tissue.

The use of marine aquaculture solid waste for nursery production of the salt marsh plants Spartina alterniflora and Juncus roemerianus

Recent technological advances in marine shrimp and finfish aquaculture alleviate many of the environmental risks associated with traditional aquaculture, but challenges remain in cost-effective waste management. Liquid effluent from freshwater aquaculture systems has been shown to be effective in agricultural crop production (i.e., aquaponics), but few studies have explored the potential for reuse of marine aquaculture effluent, particularly the solid fraction. The purpose of this study was to investigate the use of marine aquaculture solid waste as a nutrient source for the nursery production of two salt tolerant plants commonly used in coastal salt marsh restoration, Spartina alterniflora (smooth cordgrass) and Juncus roemerianus (black needlerush). Specifically, measurements of plant biomass and tissue nitrogen and phosphorus allocation were compared between plants fertilized with dried shrimp biofloc solids and unfertilized controls, as well as between plants fertilized with dried fish solids and unfertilized controls. In both experiments, S. alterniflora plants fertilized with marine aquaculture solids showed few significant differences from unfertilized controls, whereas fertilized J. roemerianus plants had significantly greater biomass and absorbed and incorporated more nutrients in plant tissue compared to unfertilized controls. These results suggest that J. roemerianus may be a suitable plant species for the remediation of marine aquaculture solid waste.

Phosphorus Influence on Plant Tissue Nitrogen Contents and Yield Attributes of Finger Millet Varieties in Semi-arid Region of Kenya

The experiment was conducted with the aim of evaluating the effect of differential levels of P on finger millet accumulation of N and yield components. On-station experiments were conducted at the KALRO-Kiboko crops research station in Makueni County during the short and long rains of 2014 and 2015 respectively. There were 4 levels of P (0, 12.5, 25 and 37.5 kg ha-1 P2O5) and three varieties (U-15, P-224 and Ekalakala). Ekalakala was the local check while 0 kg/ha P2O5 was the control. The trial was laid out in a randomized complete block design and fitted in factorial arrangement with three replicates given a total of 36 plots. Soil sampling was at a depth of 0-30 cm on all the plots and analytical results showed moderately available P but very low N, organic carbon and zinc. Significant differences (P=.05) were observed between the phosphate levels on the nitrogen contents in plant parts with the control showing the lowest N accumulation of 4.95% and 4.90% for the short and long rains respectively while the 25 kg ha-1 P2O5 rate had the highest with 5.66% in the short rains and 5.14% in the long rains. The stem contained the highest nitrogen content while the roots had the lowest. Phosphate rates did not have significant influence on the yield components except the finger width while the varieties varied significantly (P=.05) on the productive tillers, panicle number, grains per spikelet and the harvest index. Variety U-15 had the highest yield for both seasons with a maximum of 3410 kg ha-1 for the short rains. The newly released variety (U-15) responded well to moderate P supplemented at 25 kg ha-1 P2O5 thus can efficiently utilize N in soils with low N like in Makueni and is highly recommended. The optimal P for the yield and N accumulation was 25 kg ha-1 P2O5 and beyond this point the P would not be translated to profitable yield but a loss to the farmer in the short run.

Increased resistance to a generalist herbivore in a salinity-stressed non-halophytic plant.

Plants often grow under the combined stress of several factors. Salinity and herbivory, separately, can severely hinder plant growth and reproduction, but the combined effects of both factors are still not clearly understood. Salinity is known to reduce plant tissue nitrogen content and growth rates. Since herbivores prefer tissues with high N content, and biochemical pathways leading to resistance are commonly elicited by salt-stress, we hypothesized that plants growing in saline conditions would have enhanced resistance against herbivores. The non-halophyte, Brassica juncea, and the generalist herbivore Trichoplusia ni were used to test the prediction that plants subjected to salinity stress would be both more resistant and more tolerant to herbivory than those growing without salt stress. Plants were grown under different NaCl levels, and either exposed to herbivores and followed by removal of half of their leaves, or left intact. Plants were left to grow and reproduce until senescence. Tissue quality was assessed, seeds were counted and biomass of different organs measured. Plants exposed to salinity grew less, had reduced tissue nitrogen, protein and chlorophyll content, although proline levels increased. Specific leaf area, leaf water content, transpiration and root:shoot ratio remained unaffected. Plants growing under saline condition had greater constitutive resistance than unstressed plants. However, induced resistance and tolerance were not affected by salinity. These results support the hypothesis that plants growing under salt-stress are better defended against herbivores, although in B. juncea this may be mostly through resistance, and less through tolerance.

Biomass Production, Tissue Nutrient Concentration, and N2-Fixing Potentials of Seven Tropical Leguminous Species

Two pot experiments were conducted in the screenhouse of Forestry Research Institute of Nigeria, Ibadan (7° 30′ N and 3° 54′ E), southwestern Nigeria, to assess seven nitrogen-fixing shrub and tree legumes (NFTs) for their biomass production, N2-fixing potentials, and tissue nutrient concentration in two soil types. The purpose of the study was to identify an NFT that has the greatest potential for agroforestry alley cropping system and biochar production for sustainable soil productivity and crop production. The results indicated that plant growth rate, biomass production, and N2-fixing potential of the plants differed significantly with plant species but not with soil types, while the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in plant tissues, in most cases, varied significantly with plant species, plant parts, and soil types. Total biomass was greatest for Gliricidia sepium in both Ultisol and Alfisol, whereas Acacia auriculaeformis produced the smallest biomass in both soils. Gliricidia sepium and Leucaena leucocephala had the least %NdfF (percent N derived from fertilizer), 4.8 and 4.2, respectively, in the two soils, whereas Faidherbia albida and Acacia auriculaeformis had the highest %NdfF of 9.6 in the Ultisol and 7.4 in the Alfisol respectively. Significant negative correlations were established between plant biomass and %NdfF in the Ultisol (−0.888**) and Alfisol (−0.898**). Based on total biomass, shoot N concentration and %NdfF, the NFTs were ranked with Gliricidia rated highest in the two soils as having the greatest potential for alley cropping and biochar production, closely followed by Leucaena, while Acacia auriculaeformis had the lowest potential in both soil types.