High Nitrogen Rates Research Articles

Effects of nitrogen application rates on the spatio-temporal variation of leaf SPAD readings on the maize canopy

AbstractThe spatio-temporal variation of leaf chlorophyll content is an important crop phenotypic trait that is of great significance for evaluating crop productivity. This study used a soil-plant analysis development (SPAD) chlorophyll meter for non-destructive monitoring of leaf chlorophyll dynamics to characterize the patterns of spatio-temporal variation in the nutritional status of maize (Zea maysL.) leaves under three nitrogen treatments in two cultivars. The results showed that nitrogen levels could affect the maximum leaf SPAD reading (SPADmax) and the duration of high SPAD reading. A rational model was used to measure the changes in SPAD readings over time in single leaves. This model was suitable for predicting the dynamics of the nutrient status for each leaf position under different nitrogen treatments, and model parameter values were position dependent.SPADmaxat each leaf decreased with the reduction of nitrogen supply. Leaves at different positions in both cultivars responded differently to higher nitrogen rates. Lower leaves (8th–10th positions) were more sensitive than the other leaves in response to nitrogen. Monitoring the SPAD reading dynamic of lower leaves could accurately characterize and assess the nitrogen supply in plants. The lower leaves in nitrogen-deficient plants had a shorter duration of high SPAD readings compared to nitrogen-sufficient plants; this physiological mechanism should be studied further. In summary, the spatio-temporal variation of plant nitrogen status in maize was analysed to determine critical leaf positions for potentially assisting in the identification of appropriate agronomic management practices, such as the adjustment of nitrogen rates in late fertilization.

Optimized nitrogen rate, plant density, and irrigation level reduced ammonia emission and nitrate leaching on maize farmland in the oasis area of China.

Nitrogen fertilizers play a key role in crop production to meet global food demand. Inappropriate application of nitrogen fertilizer coupled with poor irrigation and other crop management practices threaten agriculture and environmental sustainability. Over application of nitrogen fertilizer increases nitrogen gas emission and nitrate leaching. A field experiment was conducted in China’s oasis irrigation area in 2018 and 2019 to determine which nitrogen rate, plant density, and irrigation level in sole maize (Zea mays L.) cropping system reduce ammonia emission and nitrate leaching. Three nitrogen rates of urea (46-0-0 of N-P2O5-K2O), at (N0 = 0 kg N ha−1, N1 = 270 kg N ha−1, and N2 = 360 kg N ha−1) were combined with three plant densities (D1 = 75,000 plants/ha−1, D2 = 97,500 plants/ha−1, and D3 = 120,000 plants/ha−1) with two irrigation levels (W1 = 5,250 m3/hm2 and W2 = 4,740 m3/hm2) using a randomized complete block design. The results showed that, both the main and interaction effects of nitrogen rate, plant density, and irrigation level reduced nitrate leaching (p < 0.05). In addition, irrigation level × nitrogen rate significantly (p < 0.05) reduced ammonia emission. Nitrate leaching and ammonia emission decreased with higher irrigation level and higher plant density. However, high nitrogen rates increased both nitrate leaching and ammonia emission. The study found lowest leaching (0.35 mg kg−1) occurring at the interaction of 270 kg N ha−1 × 120,000 plants/ha−1 × 4,740 m3/hm2, and higher plant density of 120,000 plants/ha−1 combined with 0 kg N ha−1 and irrigation level of 5,250 m3/hm2 recorded the lowest ammonia emission (0.001 kg N)−1. Overall, ammonia emission increased as days after planting increased while nitrate leaching decreased in deeper soil depths. These findings show that, though the contributory roles of days after planting, soil depth, amount of nitrogen fertilizer applied and year of cultivation cannot be undermined, it is possible to reduce nitrate leaching and ammonia emission through optimized nitrogen rate, plant density and regulated irrigation for agricultural and environmental sustainability.

EVALUATING QUINOA LODGING RISK AND YIELD UNDER DIFFERENT IRRIGATION THRESHOLDS, NITROGEN RATES AND PLANTING DENSITIES IN NORTH-WESTERN CHINA

<List> <ListItem><ItemContent> ● A moderate irrigation threshold of −25 kPa gave the greatest actual yield. </ItemContent></ListItem> <ListItem><ItemContent> ● Nitrogen rates of 80−160 kg·ha⁻¹ reduced lodging risk without yield decrease. </ItemContent></ListItem> <ListItem><ItemContent> ● Planting density of 30 plants·m⁻² provided both high yield and lodging resistance. </ItemContent></ListItem> <ListItem><ItemContent> ● A lower-stem lodging index was best for prediction of quinoa lodging risk. </ItemContent></ListItem></List> Lodging is a major yield-limiting factor of quinoa production. In 2018 and 2019, the orthogonal field experiments were conducted to investigate the responses of quinoa lodging risk and yield to irrigation threshold (soil matric potential of −15, −25 and −55 kPa), nitrogen rate (80, 160 and 240 kg·ha⁻¹) and planting density (20, 30 and 40 plants m⁻²). Results showed that high irrigation thresholds and nitrogen rates significantly (<i>P</i> < 0.05) increased plant height and fresh weight per plant, and high planting densities reduced stem diameter and strength, all of those led to significantly ( <i>P</i> < 0.05) high lodging risks. The −15 and −55 kPa treatments gave the lowest actual yield ( <i>P</i> < 0.05) in 2018 and 2019, respectively. Higher lodging rate with a nitrogen rate of 240 kg·ha⁻¹ resulted in a lower actual yield than 80 and 160 kg·ha⁻¹ in both years. Planting density of 30 plants m⁻² gave a significantly (<i>P</i> < 0.05) greater estimated yield than 20 plants m⁻² and had a lower lodging rate than 40 plants m⁻², resulting in the maximum actual yield among planting densities. In conclusion, a moderate irrigation threshold of −25 kPa, a nitrogen rate of 80−160 kg·ha⁻¹ and an intermediate planting density of 30 plants m⁻² were determined to be best for quinoa cultivation in North-western China. In addition, the lower-stem lodging index (quarter plant height) could evaluate lodging risk more accurately than middle-stem (half plant height) or upper-stem (three quarters plant height) lodging indexes.

Yield, nutrient uptake, and economic return of faba bean (Vicia faba L.) in calcareous soil as affected by compost types

Compost application is a promising approach to improve soil fertility and the sustainability of plant production, but different types of compost may vary in their efficiency. A field experiment was carried out to evaluate the effect of traditional compost, vermicompost, and material composted with additional effective microorganisms (EM) on faba bean yield and related properties. The compost treatments were applied at three nitrogen levels (18, 27, and 36 kg ha −1 ) and compared to mineral fertilizer alone or in combination with compost in a two-factor randomized complete block design with four replicates. The economic effects of the different composts were assessed using partial budget analysis. All three composts resulted in significantly higher grain and biomass yields, as well as nutrient uptake into grain compared to mineral fertilizer. This was reflected in a higher number of nodules and higher residual soil nitrogen in the compost treatments. However, EM and vermicompost were most efficient, with a yield of approximately 3.6 and 3.45 t ha −1 , respectively, compared to traditional compost with a yield of 3.1 t. Similar results were found for other investigated properties. The economic analysis revealed that EM compost application at medium and high nitrogen rates was the most profitable among the treatments, with marginal rates of return varying between approximately 790 and 2800%. • EM compost and vermicompost addition resulted in significantly higher grain yield, biomass yield, number of nodules, and residual nitrogen than traditional compost and mineral fertilizer. • Nitrogen, phosphorus, and sulphur uptake into grain and straw were significantly higher on EM and vermicompost treated plots. • EM compost application based on medium and high nitrogen rates and EM compost with mineral fertilizer resulted in the best economic performance among the treatments.

In silico assessment of sowing dates and nitrogen management in common bean crops

The application of nitrogen soil fertilization is one of the factors that leads to high yields in common bean crops. Therefore, the aim of this work is to evaluate in silico the effects of nitrogen rates and topdressing dates on common bean yield in three different sowing dates and three growing seasons in Goiás State, Brazil. The CSM-CROPGRO-DRYBEAN crop model was parameterized, validated, and applied to simulate common bean yields in wet (Nov to Dec), dry (Jan to Feb), and winter (May to Jun) seasons for nitrogen rates applied at sowing and as topdressing. An economic analysis was carried out to assess the viability of each scenario. Nitrogen rate was the most important factor in the wet season in obtaining high yields. Yields increased as nitrogen rates increased. In the dry season, sowing date was the most important factor in obtaining the highest yields. However, this season presented the lowest increase in yield per kg of nitrogen, whereas the winter season presented the highest increase. In the winter season, nitrogen rate was also the most important factor in obtaining high yields, and sowing date and topdressing had a low effect on yield. The highest crop economic return was obtained with N rates (sowing/topdressing) of 60/180 kg ha−1 and 40/120 kg ha−1 for the wet and winter seasons, respectively. The bean price was fixed at US$ 0.85 kg1. Therefore, the best management strategy is an early sowing date for the dry season, high nitrogen rates and an early sowing date for the wet season, and high nitrogen rates for the winter season.

Phenotypic predictors of dent maize grain quality based on different genetics and management practices

Attempts to determine phenotypic predictors to identify high quality maize grain for different uses are noteworthy. This study aimed to assess the relationships among maize grain quality and some phenotypic characteristics of dent maize cultivars in response to various irrigation regimes (6-day and 12-day intervals), planting dates (20 June and 21 July), and nitrogen rates (0 and 184 kg ha−1), in a two-year experiment. Principal component analysis suggested that grain yield, hundred-grain weight and stem biomass were highly correlated with starch, oil and most fatty acid concentration variables. Grains per ear was the only variable correlated with amylose, protein and amino acids. Using regression tree analysis, stover yield (R2 = 0.47, P˂0.01), stem biomass at flowering (R2 = 0.74, P˂0.001), and year (R2 = 0.74, P˂0.001), were the most important variables predicting starch, oil and protein concentrations of maize grain, respectively. Data from 2019, a warmer and drier year, and high nitrogen rate were associated with higher protein and amino acids. There was a negative relationship between protein and plant height (R2 = 0.44; P˂0.001). The relationships determined in this study can give an insight to breeders and farmers for specialized farming and selecting specific quality characteristics through phenotypic predictors.

Fungal communities are more sensitive to nitrogen fertilization than bacteria in different spatial structures of silage maize under short-term nitrogen fertilization

Soil microbial diversity plays key roles in plant nutrient acquisition and resilience. In recent years, interactions between plants and their associated microorganisms in soil have decreased due to the large-scale use of chemical fertilizers. Silage maize is one of the main silage feeds with high yield and rich nutrition. However, there is a lack of knowledge on how nitrogen application affects the soil (rhizosphere and bulk soil) and endosphere microbial communities of silage maize. In this study, the effects of nitrogen application rates on bacterial and fungal communities in the bulk soil, rhizosphere, and endophytic environment of silage maize were assessed. Our results showed that microbiome assembly along the soil-root continuum is shaped predominantly by spatial structures rather than by fertilization practice. From bulk soil to endophytic environment, the effects of nitrogen application on microbial communities decreased, and bacterial diversity and network coefficient consequently reduced. Moreover, nitrogen fertilization rates significantly affected fungal alpha diversity in bulk soil and endophytic environment, and nitrogen fertilization had greater impact on fungal community composition than bacterial in different sample types. The biomarkers of fungi sensitive to nitrogen treatment accounted for 25.5%, 11.4%, and 6.9% of all the taxonomic groups, respectively. The non-random collinearity analysis showed that Mortierellaceae, Sporormiaceae, and Geminibasidiaceae were the dominant fungal residing groups in bulk soil, rhizosphere, and endophytic environment, respectively. Therefore, the fungal community can be considered as an important indicator for silage maize in response to nitrogen application. In the N240 (240 kg N ha - 1) treatment, there was a more precise relationship between bacterial and fungal communities; however, this relationship weakened under higher nitrogen rates, and an increase in the nitrogen application rate weakened the interaction of the fungal community.

Long-term fertilization with high nitrogen rates decreased diversity and stability of diazotroph communities in soils of sweet potato

Sweet potato (Ipomoea batatas Lam) could produce acceptable root yield in low-nitrogen (N) soils, with substantial N uptake potentially attributed to supplies provided via biological N2-fixation by free-living diazotrophs. However, dynamics of diazotrophic communities as influenced by soil properties across the N fertilization gradients are still largely unclear. Long-term fertilization experiment under wheat-sweet potato rotation was established in an acid yellow brown soil since 2011. Soil samples were collected after sweet potato harvest (October 2018). The nitrogenase (nifH) gene real-time polymerase chain reaction (RT-PCR) and Hiseq high-throughput sequencing technologies were applied to soil samples from four N fertilizer treatments (0, 60, 120 and 180 kg ha−1). The results showed that long-term N fertilization significantly decreased abundance of the nifH gene, which was closely related to decreases in the content of available phosphorus (AP). The long-term high-N (120 and 180 kg ha−1) fertilization dramatically altered structure of soil diazotrophic community and lead to in decreased diversity of diazotrophs, whereas low-N (60 kg ha−1) fertilization maintained diazotrophic community diversity and stability. Compared with the low-N fertilizer inputs (0 and 60 kg ha−1), the high rates of N fertilization (180 kg ha−1) significantly decreased the relative abundance of nifH-harboring microorganisms, especially the phylum Cyanobacteria known as potential N2-fixers that could sustain fertility of sweet potato soils. There were negative correlations between N fertilization rates and the relative abundance of Proteobacteria, whereas the Bacteroidetes and Firmicutes showed a positive correlation. Moreover, the structural equation model (SEM) results suggested that the diazotrophic community diversity and structure were influenced mostly by soil pH rather than SOM and N forms (TN, NH4+-N and NO3−-N), and diazotrophs abundance mainly regulated by soil AP content. Our results implied that appropriate N fertilization is beneficial to sustain the stability and diversity of the diazotrophic community.

Nitrogen processing by treatment wetlands in a tropical catchment dominated by agricultural landuse

Agriculture is a major contributor to marine nitrogen pollution, and treatment wetlands can be a strategy to reduce it. However, few studies have assessed the potential of treatment wetlands to mitigate nitrogen pollution in tropical regions. We quantify the nitrogen removal rates of four recently constructed treatment wetlands in tropical Australia. We measured denitrification potential (Dt), the inflow-outflow of nutrients, and tested whether the environment in these tropical catchments is favourable for nitrogen removal. Dt was detected in three of the four systems with rates between 2.0 and 12.0 mg m-2 h−1; the highest rates were measured in anoxic soils (ORP −100 to 300 mV) that were rich in carbon and nitrogen (>2% and >0.2%, respectively). The highest nitrogen removal rates were measured when NO3−-N concentrations were >0.4 mg L−1 and when water flows were slow. Treatment wetlands in tropical regions can deliver high removal rates of nitrogen and other pollutants when adequately managed. This strategy can reduce nutrient loads and their impacts on sensitive coastal zones such as the Great Barrier Reef.

Purification effect of bioretention with improved filler on runoff pollution under low temperature conditions

In recent years, there have been a number of studies on bioretention during hot summer, with only few studies reported during low-temperature winters. The application of bioretention in cold areas still lacks effective guidance. In this study, runoff simulation experiments were conducted to explore the influence of wood chips filler and water treatment residue on the removal of runoff pollutants under different packing gradations and low temperature conditions. Under low temperature, nitrate nitrogen removal rate of wood chips filler decreased from 70% to 90% in autumn to −23%- 35% in winter, the total nitrogen removal rate decreased from 75 to 90% in autumn to 20%–50% in winter, the removal rate of ammonia nitrogen and total phosphorus exceeded 70% during the entire experiment. Water treatment residue filler maintained a high ammonia nitrogen and total phosphorus removal rate during the experiment, with the total phosphorus removal rate above 90% and ammonia nitrogen removal rate above 80%. The bioretention effluent concentration of nitrate and total nitrogen was higher than 7.3 mg/L and 8.5 mg/L, respectively, most of the time. However, at low temperature, the COD removal rate of the two fillers was 25%–50%, which was very poor. Therefore, wood chips filler was observed to be better suited for the removal of nitrate and total nitrogen from the runoff, while water treatment residue had a better effect on the removal of ammonia nitrogen and total phosphorus in winter. Thus, for the application of bioretention in northern China, appropriate fillers should be selected considering the water quality characteristics of the area.

Assessment of grey water footprint in paddy rice cultivation: Effects of field water management policies

Excessive use of fertilizers and manure has detrimentally affected surface and ground water resources due to high rates of nitrogen (N) deposition. Reducing the nitrogen-related grey water footprint (GWF) is crucial, otherwise it may lead to severe food production-related water pollution and a reduction in freshwater absorption capacity. This study explored the feasibility of farmland water management policies (WMPs) for GWF regulation in paddy rice fields. Four WMPs—frequent shallow irrigation (FSI), wet and shallow irrigation (WSI), controlled irrigation (CI), and rain-catching and controlled irrigation (RCCI)—were analyzed based on daily field water balance and nitrogen transportation in Nanjing, China. The results showed that GWF varied among the four WMPs. During 2015–2017, the GWF values under FSI, WSI, CI, and RCCI policies were 303.6, 366.4, 369.5, and 218.3 mm, respectively. The GWF under RCCI was the smallest for all the years, that under CI was the highest in the wet year (2016), and that under FSI was the highest in the dry year (2017). GWF increased with an increase in total field water inflow and precipitation. Additionally, changes in the irrigation and drainage methods could regulate and decrease GWF. Pollutant leaching risk increased with rising precipitation, which could be mitigated by reducing drainage in the early stages of growth. In East China, RCCI was observed to be the best policy for managing field water in paddy production with regard to GWF reduction. The findings of this study can aid in agricultural water resource management.

Nonlinear dependency of N2O emissions on nitrogen input in dry farming systems may facilitate green development in China

China's green development has advanced national strategic requirements for excessive nitrogen application, greenhouse gas emission reduction, and efficient production in food systems. However, large challenges still exist in achieving these goals. In this study, a comprehensive meta-analysis and random forest identification were conducted to integrate nitrogen fertilization based nitrous oxide (N2O) emission data from field experiments in the dry farming system of China (DFSC), and to analyze the dependency of N2O emissions and crop yield on nitrogen inputs. We then quantified the potential reasonable nitrogen dose in the DFSC that would simultaneously reduce N2O emissions and favor China’s green development. The results showed an absolute impact of nitrogen input on N2O emissions, and a significant nonlinear response between N2O emissions and nitrogen dose in the DFSC. However, the crop yield exhibited a different pattern: yields of cereal and cash crops in response to nitrogen input were modeled by a quadratic polynomial, especially at extremely high nitrogen rates (>300 kg N ha−1 for cereals and >600 kg N ha−1 for cash crops). The yield enhancing effect tended to be flat or even decrease. We propose to achieve a reasonable nitrogen dose by reducing the 1/3 nitrogen surplus in the DFSC, according to the various soil-climatic conditions. For cereal, cash, vegetable, tea and orchard crops, the values should be 98.72 – 133.46, 67.66 – 107.4, 258.53 – 470.57, 159.61–296.09 and 269.08–383.48 kg N ha−1, respectively. The findings of our investigation indicate that implementation of a reasonable nitrogen dosage will not give rise to a large yield decrease and will better contribute to meeting the requirements of N2O mitigation and a national green development strategy.

Synergy between autotrophic denitrification and Anammox driven by FeS in a fluidized bed bioreactor for advanced nitrogen removal

On the basis of the metabolic synergy between autotrophic denitrification (AuDen) and anaerobic ammonium oxidation (Anammox), the feasibility of a novel ferrous sulfide (FeS)-driven AuDen and Anammox coupled system (FS-DADAS) was investigated. The nitrogen removal performance of FS-DADAS was investigated in a lab-scale fluidized bed bioreactor fed with synthetic wastewater containing NH4+-N and NO3−-N. The results of long-term operation (120 days) demonstrated the promising performance of the system with 100% NO3−-N removal and NH4+-N concentrations lower than 8.11 mg L−1 in the effluent at a nitrogen loading rate of 0.20 g-N·(L·d)−1. Sufficient NO2−-N was provided by the AuDen for Anammox where a high removal rate of total nitrogen (TN) was achieved. The contribution of Anammox to TN removal was at >80%. The reactor could maintain a stable pH with less SO42− production owing to the fact that Fe(II) and S acted as electron donors. FeS gradually transformed into a sheet-like secondary mineral, FeOOH. AuDen (Thiobacillus) and Anammox bacteria (Candidatus Kuenenia) were successfully retained in the bioreactor, with relative abundance values of 18.82%–23.64% and 3.52%–8.67%, respectively. FS-DADAS is a promising technology for the complete removal of TN from wastewaters with low C/N ratios at low energy consumption.

The influence of nitrogen doses on yield and yield properties of safflower (Carthamus tinctorius) varieties under micro-climate conditions of Igdir plain – Turkey

The growth and development of safflower are affected by several factors such as genotype, agronomic practices, and environmental conditions. One of the most important agronomic practices is fertilization. As a fertilizer, nitrogen is a basic element required for successful plant growth. In the study, it was aimed to determine the effects of different nitrogen doses (0, 100, 150, and 200 kg ha−1) on yield and yield properties of three safflower varieties (Remzibey-05, Dinçer, and Yenice) under micro-climate conditions in the Iğdır University Agricultural Research fields, Turkey during 2012 − 2013 according to the split-plot experimental design in randomized blocks with three replications. The investigation denoted that the differences among the varieties were found significant for all attributes except seed number per head. And also, the effect of differences between observation years and the effects of nitrogen rates were determined to be significant for all observed properties. Increasing the nitrogen rate increased all observed attributes. Seed oil content increased with nitrogen applications up to 100 kg ha−1 but reduced again in higher nitrogen rates. In the study, the interactions of both factors had no significant effects on all observed attributes. The results of two years study show that the Yenice safflower cultivar as an alternative oil plant and the most economical nitrogen dose of 150 kg ha−1 can be suggested for the maximum yield in the unit area where the experiment is carried out and in other regions with similar climatic conditions.

Soil amendments and fumigation for the management of Fusarium wilt of bunching spinach in Ontario, Canada

Fusarium wilt, caused by Fusarium oxysporum f. sp. spinaciae, is a significant constraint to the summer production of bunching spinach in Ontario, Canada. Trials were conducted to assess soil amendments (limestone) and fumigants (metam sodium, chloropicrin and dazomet) for the suppression of Fusarium oxysporum f. sp. spinaciae. Dolomitic limestone applied at a rate of 10 and 20 t ha−1 reduced the incidence of fusarium wilt by 10 and 47%, respectively, even though there was little change in soil pH (7.4–7.5) or soil calcium concentration (1598 vs 1483 in 20 t lime vs control, respectively. Fusarium wilt severity was lower in the 2013 than in the 2014 growing season. In 2014, the fumigants metam sodium, chloropicrin and dazomet reduced the population of Fusarium spp. propagules in the soil by 84, 93 and 100%, respectively. Chloropicrin provided the best control of the spinach fusarium wilt pathogen compared to the other fumigants but was only assessed one year. Chloropicrin was the only treatment to truly reduced spinach Fusarium wilt by preventing vascular discolouration. Brassica juncea and calcium cyanamide were not effective at suppressing the disease. A high rate of nitrogen, consisting of polymer coated sulphur coated urea, was applied to provide the same rate of nitrogen as the Brassica juncea and calcium cyanamide treatments. Applying nitrogen in this formulation was as effective as metam sodium in reducing the incidence and severity of Fusarium wilt and should be evaluated further to determine the economics and environmental impact of this approach.

Agricultural intensification and climate change have increased the threat from weeds.

Weeds represent a significant threat to crop yields and global food security. We analysed data on weed competition from the world's longest running agricultural experiment to ask whether potential yield losses from weeds have increased in response to management and environmental change since the advent of the Green Revolution in the 1960s. On plots where inorganic nitrogen fertiliser has been applied, potential yield losses from weeds have consistently increased since 1969. This was explained by a warming climate, measured as air temperature averaged over the growing season for the weeds, and a shift towards shorter crop cultivars. Weeds also reduced yield proportionally more on plots with higher rates of nitrogen which had higher yields when weeds were controlled; the relative benefit of herbicides was, therefore, proportional to potential crop yield. Reducing yield losses from weed competition is increasingly challenging because of the evolution of herbicide resistance. Our results demonstrate that weeds now represent a greater inherent threat to crop production than before the advent of herbicides and integrated, sustainable solutions to weed management are urgently needed to protect the high yield potential of modern crop genotypes.

The Role of Engineering Thermodynamics in Explaining the Inverse Correlation between Surface Temperature and Supplied Nitrogen Rate in Corn Plants: A Greenhouse Case Study

Nitrogen stress plays a critical role in corn yield reduction. Thermal remote sensing has many applications: as an assessment tool for urban heat island, as an ecological indicator of ecosystem development, and as a water-stress-detection tool. In this study, it was hypothesized that corn crops supplied with optimum or high rates of nitrogen would have lower surface temperatures compared to corn grown under nitrogen-stressed conditions. Two experiments were conducted in the greenhouse at the University of Guelph, Canada, from the period between 2015 and 2016, involving three rates of nitrogen (high, medium, and low rates) supplied to corn plants after seed emergence. Leaf and whorl temperatures were collected by using a high-resolution thermal camera, an infrared handheld point measurements gun, and a type T thermocouple, respectively. An approximate difference of 2 °C was observed in temperatures between plants receiving high and low rates of nitrogen. These results supported the hypothesis that nitrogen-stressed plants have higher temperatures compared to less stressed plants, at a 0.05 significance level. This study investigated the application of the exergy destruction principle through thermal remote sensing, to detect crop stress at early growth stages under greenhouse conditions, to increase the production and reduce the harmful environmental impact.

Principal component analysis of steers performance and structural and nutritional characteristics of Mombasa grass

ABSTRACT: There is little information about whether the increased secondary productivity observed in pastures fertilized with high nitrogen rates is attributable to fluctuations in the nutritional value or pasture structural characteristics, or both. This study aimed to identify a set of factors (structural and nutritional characteristics) that best explain the performance of beef steers grazing Mombasa grass pastures under residual effects of nitrogen fertilizer. The data were collected in Mombasa grass pastures fertilized with increasing rates of nitrogen (N) (100, 200 and 300 kg ha-1) from 2015 to 2017. In 2018, nitrogen fertilization was not used in order to characterize a residual effect of the nutrient. Variables related to pasture structural characteristics such as forage accumulation rate (FAR), canopy height, forage mass (FM) and morphological components were evaluated. The study also evaluated the nutritional value of leaf blades and the performance of beef steers based on average daily gain (ADG) and stocking rate. Principal component analysis was performed using the dataset available. Most of the variance (99.6%) was explained by only two principal components (PCs), of which 90.0% corresponded to PC1. The most influential parameters for PC1, in order of priority, were: FAR, FM, leaf blade and stem masses. These variables were positively associated with stocking rate. Conversely, ADG was not associated with any variable. ADG was the most relevant variable for the second PC; however, this PC explained less variance (9.6%). The structural characteristics of the pasture (FAR, FM and morphological components mass) better explain the fluctuations in the performance of cattle on pastures of Mombasa grass under residual effects of nitrogen fertilizer. The stocking rate is an efficient parameter to support decision-making in managed pastures with variable stocking.

Spring camelina: Effect of mineral fertilization on the energy efficiency of biomass production

The aim of this study was to determine the effect of nitrogen (0, 40, 80, 120, 160 kg ha−1) and sulfur (0, 15, 30 kg ha−1) fertilization on the energy efficiency ratio of spring camelina produced in north-eastern Poland. The energy inputs in the production of camelina ranged from 5.1 (without nitrogen and sulfur fertilization) to 17.7 GJ ha−1 (160 kg N ha−1 and 30 kg S ha−1). The energy output of camelina produced without nitrogen or sulfur fertilizers was determined at 28.38 (seeds) and 61.53 GJ ha−1 (seeds and straw). High rates of nitrogen and sulfur fertilization increased the energy output of camelina seeds and biomass by up to 186% and 155%, respectively. Nitrogen fertilizer applied at 120 kg ha−1 decreased the energy efficiency ratio by 49% in seeds and by 55% in total biomass. The application of sulfur increased the energy efficiency ratio of seeds by 1–8%, and the energy efficiency ratio of total biomass by 1–5%. Sulfur enhanced the energy efficiency ratio of camelina in production technologies with high rates of nitrogen fertilization.

A hybrid decision tool for optimizing broccoli production in a changing climate

Climatic changes are already influencing the frequency, magnitude, and duration of extreme weathers (e.g. drought) in California. California is a leading state for vegetable production in United States (U.S.). Since vegetables are very sensitive to extreme weathers, it is critical to evaluate the effects of climate change on yield and to find the potential adaptive management strategies for the sustainable vegetable production. The objectives of this study were to develop a plant-oriented cropping model to evaluate the impacts of different cropping managements on yields under various climate condition and atmospheric CO2 levels. To improve modeling performance, numerous previous studies that reported broccoli yields in different managements were used. After model calibration and validation, 560 scenarios under the conditions of combinations of climate changes, four broccoli cultivars, five nitrogen fertilizer application rates, and four plant densities were simulated in two study locations in Monterey County, CA where produces almost 40% of total California broccoli production. Based on results from 33,600 simulations, broccoli yields were highly related to nitrogen fertilizer application. However, at high nitrogen rates (above 75 kg N ha−1), yields were barely changed. In general, under stressful conditions, all cultivars produced their maximum yields at low plant density, and their yields did not respond to addition of nutrient in soil. However, CO2 enrichment and warmer temperature under RCP8.5 pathways, yield responded positively with fertilizer application rate and plant density. It seems likely that the effects of cropping managements will depend upon CO2 level and temperature.