Levels Of Nitrogen Fertilizer Application Research Articles

Method for Monitoring Wheat Growth Status and Estimating Yield Based on UAV Multispectral Remote Sensing

An efficient and accurate estimation of wheat growth and yield is important for wheat assessment and field management. To improve the accuracy and stability of wheat growth and yield estimation, an estimation method based on a genetic algorithm-improved support vector regression (GA-SVR) algorithm was proposed in this study. The correlation analysis between vegetation indices calculated from spectral data and wheat growth phenotypes and yields was performed to obtain the optimal combination of vegetation indices with high correlation and good estimation performance. At the same time, the optimal model for wheat growth monitoring was screened and constructed in experiments with 12 wheat varieties and 3 gradient nitrogen fertilizer application levels. Then, the yield estimation model was established and its applicability was verified under different nitrogen fertilizer application levels. The results showed that the constructed models for the leaf area index, plant height, and yield estimation performed well, with coefficients of determination of 0.82, 0.71, and 0.70, and root mean square errors of 0.09, 2.7, and 68.5, respectively. This study provided an effective UAV remote sensing technique for monitoring wheat growth status and estimating yield. This study provides an effective unmanned aerial remote sensing technique for monitoring wheat growth and estimating yield, and provides technical support for wheat yield assessment and field management.

Impacts of the tillage systems on the production of green corn (Zea mays L.) in long‐term plots in Northeastern Brazil

AbstractIn the current global context of climate change and the increasing demand for sustainability, optimizing agricultural production is very important in order to meet the demands for food and to mitigate environmental impact. To achieve sustainable agricultural production, particularly in regions with tropical soil and climate conditions, is necessary to adopt conservation‐oriented techniques. This includes no‐tillage system, the use of soil‐cover crops, and the application of inoculants. The objective of this research was, at the end of the 22nd cropping season, to assess the influence of soil compaction in the production of green corn (Zea mays L.) in a long‐term field experiment. This study was conducted under different soil tillage systems in a Red‐Yellow Ultisol from the Coastal Tablelands of northeastern Brazil. Three soil tillage systems were applied: Conventional Tillage (CT), Minimum Tillage (MT), and No‐tillage (NT). These were combined with four previous crops: cowpea (Vigna unguiculata), crotalaria (Crotalaria juncacea), pigeon pea (Cajanus cajan), and millet (Pennisetum glaucum), as well as two levels of nitrogen fertilizer application: (1) 100% of the recommended N dose, and (2) 50% of the recommended N dose plus Azospirillum brasilense inoculant. The experimental design consisted of strip plots with subplots divided and randomized within each strip, with three replications. Soil compaction was assessed using parameters of soil density (SD) and soil mechanical resistance to penetration (MRP) in conjunction with moisture content (MC). The principal component analysis (PCA) highlighted that conservation‐oriented systems exhibited greater soil organic carbon (SOC) levels, leading to increased productivity of commercial green corn cobs. The synergistic effect of diversifying previous crops and adopting conservation tillage systems, especially in soils under long‐term tillage, resulted in heightened productivity of commercial green corn ears.

Effects of Intercropping and Nitrogen Application on Soil Fertility and Microbial Communities in Peanut Rhizosphere Soil

The intercropping of peanuts and sugarcane is a sustainable planting model that deserves in-depth research. For this study, two variables, i.e., intercropping status (peanut monocropping or sugarcane/peanut intercropping) and the level of nitrogen fertilization (low, medium, or high), were evaluated to analyze the effects of intercropping and nitrogen application on soil fertility and microbial communities in peanut rhizosphere soil. These analyses revealed that higher nitrogen application led to increased total nitrogen (TN), available nitrogen (AN), and soil organic matter (OM) levels in rhizosphere soil for both monocropped and intercropped peanuts, with a decrease in pH. Monocropped peanuts had higher TN, total phosphorus (TP), and total potassium (TK) levels compared to intercropped peanuts at the same nitrogen level but lower AN content and pH levels. The diversity of microbial communities in the rhizosphere soil of intercropped peanuts was significantly higher than that of monocropped peanuts under high levels of nitrogen fertilizer application. Higher levels of Gemmatimonadetes abundance were observed in intercropping rhizosphere soil, compared to that associated with peanut monocropping under low, middle, and high levels of nitrogen fertilizer application, whereas the opposite trend was observed for Chloroflexi abundance. Nitrospira abundance levels rose gradually in the monocropping treatment group, whereas the opposite trend was evident under intercropping conditions. Further analyses of nitrogen cycle-related genes demonstrated higher levels of nitrogen conversion cycle activity in intercropping peanut rhizosphere soil under low nitrogen levels, whereas nitrogen transformation cycle activity levels were higher in monocropping peanut rhizosphere soil under high levels of nitrogen amendment. It can be concluded that intercropping and nitrogen fertilizer application change the physical and chemical properties of soil, thus affecting the diversity and function of soil microbial communities in the peanut rhizosphere. These results offer a theoretical foundation for more efficient sugarcane/peanut intercropping systems.

Assessing the impacts of climate change on crop yields, soil organic carbon sequestration and N2O emissions in wheat–maize rotation systems

Straw retention has been widely implemented to increase soil organic carbon (SOC) sequestration and greenhouse gas (GHG) mitigation for global agriculture. However, the combined effects of long-term straw retention on crop production, SOC sequestration and GHG emissions response to climate change remain unknown. Two nearby wheat–maize rotation field experiments in the North China Plain, combined with local weather, soil and agronomic measurements, were used to evaluate the applicability of the SPACSYS model. The model was then applied to assess the response of crop yield, SOC storage and nitrous oxide (N2O) emissions to three nitrogen fertilizer application levels (100, 200, 400 kg N ha−1) and three representative concentration pathway scenarios (RCP2.6, RCP4.5 and RCP8.5) under straw retention for the wheat–maize rotation systems during 2021–2100. In general, the model was reasonably accurate with R2 and model efficiency (EF) ranging from 0.25 to 0.96 and 0.32–0.94, respectively. Climate change decreased wheat yield by 4–39%, while maize showed a slight increase (3%) under RCP2.6 and a decrease of 1–15% under RCP4.5 and RCP8.5. The SOC storage in the 0–20 cm soil increased at a rate of 73–195 kg C ha−1 yr−1 but decreased within the upper 1 m soil at 280–390 kg C ha−1 yr−1. Climate change reduced the positive effect of SOC sequestration except in RCP2.6 and stimulated substantial N2O emissions ranging from 1–7.5 to 2.9–23.2 kg N ha−1 yr−1, consequently, the global warming potential increased from –79–2555 to 548–9357 kg CO2-eq ha−1 yr−1 under various N fertilizer application levels. This study reveals that the negative feedback under climate change with modelling approach, and extensive efforts are needed to make adaptations to ensure food production and reduce GHG emissions in the future.

The differences in metabolites, starch structure, and physicochemical properties of rice were related to the decrease in taste quality under high nitrogen fertilizer application

Nitrogen fertilizer application is one of the key cultivation practices to improve rice yields. However, the application of high nitrogen fertilizers often leads to a reduction in the stickiness of the rice after cooking, thus reducing the taste quality of rice. Moreover, there are differences in taste quality among rice varieties, and the mechanism has not been studied in depth. In this study, two rice varieties (Meixiangzhan2hao and Exiang2hao) were planted under two nitrogen fertilizer levels. The physicochemical properties and taste quality of the rice were determined after maturity. Our results showed that high nitrogen fertilizer level alters tryptophan metabolism in rice, increasing most amino acid content and protein content in rice. The high content of protein and the higher short-range ordered structure of starch inhibited the gelatinization characteristics of starch and reduced the taste quality of rice. Under high nitrogen fertilizer application, Exiang2hao showed smaller increases in protein content, lower level of amylose and relative crystallinity, and higher content of lipid metabolites. These differences in chemical substances resulted in a less pronounced reduction in the taste quality of Exiang2hao. In this study, the taste quality of different rice varieties under different levels of nitrogen fertilizer application was analyzed, providing new ideas for future improvement of rice taste quality.

Response of Soil Environment and Microbial Community Structure to Different Ratios of Long-Term Straw Return and Nitrogen Fertilizer in Wheat–Maize System

To determine the reasonable rate of straw return and nitrogen (N) fertilizer use which may maintain soil ecosystem health, we analyzed their soil microbial biomass and composition in a 10-year field experiment with different rates of straw return (50%, 100%) and N fertilizer (270, 360, 450, 540 kg N ha−1 yr−1) by phospholipid fatty acid (PLFA) analysis and high-throughput sequencing. A rate of 50% straw return combined with 450 or 540 kg N ha−1 yr−1 effectively increased the soil available nutrient contents mainly for total nitrogen, available potassium, and available phosphorus. Total PLFAs indicated that straw return combined with N fertilizer promoted soil microbial growth and increased biomass. A rate of 100% straw return with 450 kg N ha−1 yr−1 was not conducive to the stability of the soil ecosystem according to the ratio of fungi to bacteria (F:B). The similar rate of straw returning and the similar level of nitrogen fertilizer application will be divided into the same cluster using a heatmap analysis. Some saprophytic fungi or pathogens became the dominant fungi genera, such as Gibberella, Sarocladium, Pseudallescheria, and Mycosphaerella, in the treatments with 100% straw returning combining higher N fertilizer (>450 kg ha−1 yr−1 yr−1 added). The relative abundances of some heavy metal-tolerant bacteria, such as those in Proteobacteria and Chlorobi, increased in the soils in the 100% straw return treatments. Therefore, the combined application of 100% straw returning and higher N fertilizer (>450 kg ha−1 yr−1) added long-term was not appropriate for soil health, which will lead to the risk of disease and pollution in soil.

Irrigation Regimes and Nitrogen Rates as the Contributing Factors in Quinoa Yield to Increase Water and Nitrogen Efficiencies.

Sustainable field crop management has been considered to reach the food security issue due to global warming and water scarcity. The effect of deficit irrigation and nitrogen rates on quinoa yield is a challenging issue in those areas. In this regard, the interaction effects of different N rates (0, 125, 250, and 375 kg N ha−1) and irrigation regimes [full irrigation (FI) and deficit irrigation at 0.75 FI and 0.5 FI] on quinoa yield and water and nitrogen efficiencies were evaluated with a two-year field experiment. Increasing nitrogen fertilizer application levels from 250 to 375 kg N ha−1 under FI and deficit irrigation did not cause a significant difference in seed yield and the total dry matter of quinoa. Furthermore, 20% and 34% reductions were observed for nitrogen use efficiency (NUE) and nitrogen yield efficiency with the application of 375 kg N ha−1 compared with that obtained in 250 kg N ha−1 nitrogen fertilizer, respectively. Therefore, a Nitrogen application rate of 250 kg ha−1 and applying 0.75 FI is suggested as the optimum rate to reach the highest seed water use efficiency (0.7 kg m−3) and NUE (0.28 kg m−3) to gain 4.12 Mg ha−1 quinoa seed yield. Under non–limited water resource conditions, an FI and N application rate of 375 kg ha−1 could be used for higher seed yield; however, under water-deficit regimes, an N application rate of 250 kg ha−1 could be adequate. However, questions about which environmental factors impressively restricted the quinoa growth for optimizing the potential yield need further investigation.

Smart Cover Crop Rotations: Agronomic Parameters and NK Efficiency Indices of Rice as Affected by Crop Rotations and N Applications Rates

Continuous rice transplanting without crop rotation will reduce soil positive properties and crop productions in paddy field systems. Thus, the present study aimed to investigate the effect of cover crop rotations to enhance productivity and diminished chemical fertilizer application. The experiment was conducted as split plot based on a randomized complete blocks design with four replications in north of Iran, during 2015-16 and 2016-17. Six cover crop rotations including perko-rice, buko-rice, mixed cropping of clover + ramtil + phaselia-rice, clover-rice, faba bean-rice, and fallow-rice were used as main plots. Four levels of nitrogen fertilizer application included 0, 50, 100, and 150 kg.ha-1 of urea source as sub plots. The findings revealed that the maximum lodging index was achieved for perko-rice with 150 kg urea.ha-1 . Regarding the findings of yield components, the highest paddy yield (5147 kg.ha-1 ) was achieved in perko-rice rotation with 100 kg urea ha-1 . In all crop rotations, perko-rice rotation presenting the maximum N use efficiency, N utilization efficiency, and N uptake efficiency was obtained with 100 kg urea ha-1 . Totally, it was observed that the positive effects of the cover crops in the second year was were more pronounced, where perko was more suitable than other cover crops. These findings suggest that long-term cover of these crops especially perko and buko can improve soil properties and encourage proper plant growth in paddy fields rotation, which in the long term is useful for crop production and improving qualitative parameters.

Multi-Disciplinary Assessment of Napier Grass Plantation on Local Energetic, Environmental and Socioeconomic Industries: A Watershed-Scale Study in Southern Thailand

Napier grass is an energy crop that is promising for future power generation. Since Napier grass has never been planted extensively, it is important to understand the impacts of Napier grass plantations on local energetic, environmental, and socioeconomic features. In this study, the soil and water assessment tool (SWAT) model was employed to investigate the impacts of Napier grass plantation on runoff, sediment, and nitrate loads in Songkhla Lake Basin (SLB), southern Thailand. Historical data, collected between 2009 and 2018 from the U-tapao gaging station located in SLB were used to calibrate and validate the model in terms of precipitation, streamflow, and sediment. The simulated precipitation, streamflow, and sediment showed agreement with observed data, with the coefficients of determination being 0.791, 0.900, and 0.997, respectively. Subsequently, the SWAT model was applied to evaluate the impact of land use change from the baseline case to Napier grass plantation cases in abandoned areas with four different nitrogen fertilizer application levels. The results revealed that planting Napier grass decreased the average surface runoff and sediment in the watershed. A multidisciplinary assessment supporting future decision making was conducted using the results obtained from the SWAT model; these showed that Napier grass will provide enhanced benefits to hydrology and water quality when nitrogen fertilizers of 0 and 125 kgN ha−1 were applied. On the other hand, the benefits to the energy supply, farmer’s income, and CO2 reduction were highest when a nitrogen fertilization of 500 kgN ha−1 was applied. Nonetheless, planting Napier grass should be supported since it increases the energy supply and creates jobs while also reducing surface runoff, sediment yield, nitrate load, and CO2 emission.

Вплив диференціації азотного удобрення темно-каштанового солонцюватого ґрунту на його агрохімічні показники та врожайність сільськогосподарських культур

Goal. To establish features of the influence of differentiation (address rationing) of mineral nitrogen fertilizers application on agrochemical indicators of dark chestnut weakly alkaline soil (the content of mineral nitrogen and humus) and crop yield. Methods. Field — to study the effect of gypsum and nitrogen fertilizer on the properties of dark chestnut soil and crop yields, laboratory analysis — o determine the content of mineral nitrogen and humus, mathematical — to assess the reliability of research results. Results. The application of mineral nitrogen fertilizers has led to a tendency to increase the content of mineral nitrogen in dark chestnut weakly alkaline soil. Fertilization and cultivation of crops did not affect the variability of mineral nitrogen content, which in general in the experiment remained moderate, the coefficient of variation did not change. Although the average amount of nitrogen fertilizer applied to the plots in the variant of differentiated application is 92.1 kg/ha, was less than in the plots with the maximum level of fertilizer, the yield did not differ from that with the maximum level of application and was reliably higher than in the variant with the average level of application. Conclusions. It is established that under the influence of growing crops and applying nitrogen fertilizers, the supply of dark chestnut weakly alkaline soil with mineral nitrogen improves at medium and maximum levels of fertilizer. It is established that the lack of fertilizer or low doses of nitrogen fertilizers increase the variability of the soil in terms of mineral nitrogen content, and the high level of application (390 kg/ha) for 6 years under 3 crops equalizes this indicator. There was a decrease in the variability of dark chestnut weakly alkaline soil in terms of humus content in the arable layer. A stable significant increase in the yield of grain and fodder crops depending on the levels of nitrogen fertilizer application has been also established. Differentiation of nitrogen fertilizers allows saving nitrogen fertilizers in the amount equivalent to almost 15 kg/ha of active substance per year in grain-feed 6-field crop rotation in the absence of a significant reduction in yield on dark chestnut weakly alkaline non-irrigated soils.

Biochemical mechanism of rice nitrogen promoting the resistance development of Nilaparvata lugens (Stål) to buprofezin

• Overusing nitrogen fertilizer impacts buprofezin’ efficacy to Nilaparvata lugens . • Rice nitrogen facilitates the resistance development of N. lugens to buprofezin. • Increased esterase activity may be the resistance mechanism in N. lugens . • The conclusion will improve the integrated pest and nutrient management strategies. Overusing nitrogen fertilizer not only pollute farmlands, but also make Nilaparvata lugens (Stål) less susceptible to pesticides. The current study investigated the relationship between nitrogen fertilizer application and buprofenzin resistance in N. lugens in rice by conducting a series of field efficacy tests and laboratory bioassays. The results showed that the efficacy of buprofezin decreased significantly with high level of nitrogen fertilizer application, compared to those with low or no nitrogen application in rice fields. In the laboratory, the resistance ratios of N. lugens to buprofezin, assayed at three concentrations of nitrogen (0, 1.0, 3.0 mmol/L), have developed to 14.05-, 18.40- and 25.81-fold after 20 generations of resistance selection, respectively. Meanwhile, the resistance ratios of N. lugens without buprofezin treated were 1.00-, 3.30- and 4.67-fold after 20 generations as the nitrogen concentrations increased. The enzymatic assays revealed that the activities of P450 and esterase increased significantly after resistance selection with buprofezin and nitrogen, especially on the esterase activity in N. lugens under the condition of nitrogen treatment. These results suggested that nitrogen fertilizer application contributed to the resistance development in N. lugens to buprofezin by enhancing the activity of esterase.

Excessive Nitrogen Fertilization Favors the Colonization, Survival, and Development of Sogatella furcifera via Bottom-Up Effects.

Fertilization can trigger bottom-up effects on crop plant–insect pest interactions. The intensive use of nitrogen fertilizer has been a common practice in rice production, while the yield has long been challenged by the white-backed planthopper, Sogatella furcifera (Horváth). High nitrogen fertilization can facilitate S. furcifera infestation, however, how nitrogen fertilizer leads to high S. furcifera infestation and the nutritional interactions between rice and S. furcifera are poorly understood. Here, we evaluated the effects of various levels of nitrogen fertilizer application (0–350 kg/ha) on rice, and subsequently on S. furcifera performance. We found that higher nitrogen fertilizer application: (1) increases the preference of infestation behaviors (feeding and oviposition), (2) extends infestation time (adult lifespan), and (3) shortens generation reproduction time (nymph, pre-oviposition, and egg period), which explain the high S. furcifera infestation ratio on rice paddies under high nitrogen conditions. Moreover, high nitrogen fertilizer application increased all tested rice physical indexes (plant height, leaf area, and leaf width) and physiological indexes (chlorophyll content, water content, dry matter mass, and soluble protein content), except for leaf thickness, which was reduced. Correlation analysis indicated that the specific rice physical and/or physiological indexes were conducive to the increased infestation behavior preference, extended infestation time, and shortened generation reproduction time of S. furcifera. The results suggested that nitrogen fertilizer triggers bottom-up effects on rice and increases S. furcifera populations. The present study provides an insight into how excess nitrogen fertilization shapes rice–planthopper interactions and the consequent positive effect on S. furcifera infestation.

Nitrogen fertilizer on yield of fodder maize, chemical composition, its preference and digestibility by Sokoto Gudali heifers

The lack of high yielding quality fodder for ruminant production is still a major problem to livestock sector in Nigeria. Fodder yield is primarily determined by nitrogen levels in the soil which is often limiting in tropical soils. This study evaluated four levels of nitrogen fertilizer application (0, 100, 150 and 200kg N/ha) on fodder yield of maize, chemical composition, its acceptability and digestibility by Sokoto Gudali heifers. Treatments were replicated three times on plots measuring 4mx10m in a completely randomized design. Forage was harvested at 42 days after planting (DAP) and fodder yield (tons/ha) per plot was determined. Samples of forage from each plot were taken for chemical analysis. Eight heifers were used to evaluate acceptability and twelve heifers for digestibility of the fodder using standard procedures. The biomass yield increased significantly (P<0.05) with increasing levels of nitrogen fertilizer with the highest yield (9.06tons/ha) recorded at200kgN/ha also increased significantly (P<0.05) with increased levels of nitrogen across the treatment. The highest CP (23.25%) and NDF (75.15%) were recorded at 200kg N/ha and the lowest CP(17.51%) and NDF(71.40%) at 0kgN/ha. Preference of heifers for maize fodder reduced with application of fertilizer while digestibility of the maize fodder increased up to 100kg N/ha and thereafter reduced.

Effects of Different Levels of Nitrogen Fertilizer Application Through Drip Fertigation on Sweet Corn Yield in Japan

Effects of Different Levels of Nitrogen Fertilizer Application Through Drip Fertigation on Sweet Corn Yield in Japan

Growth and Productivity of Brown Midrib Sorghum Mutant Line Patir 3.7 (Sorghum bicolor L. Moench) Treated with Different Levels of Nitrogen Fertilizer

The study aimed to determine the best of nitrogen fertilizer level based on growth and biomass production of brown midrib sorghum mutant line Patir 3.7. This research was conducted at the Field Laboratory in the Faculty of Animal Science, Andalas University, Padang. The experiment was assigned in a completely randomized block design with 4 levels of nitrogen fertilizer application and 3 replications. The treatments consisted of N0= 0 kg N ha-1 as a control; N1= 50 kg N ha-1; N2= 100 kg N ha-1; and N3= 150 kg N ha-1. Agronomic and production variables measured were plant height, stem diameter, leaf width length, leaf stem panicle ratio, stem Brix sugar content, as well as fresh biomass and nutrient production. Analysis of variance followed by Duncan Multiple Range Test (DMRT) was conducted. The results showed that the addition of nitrogen fertilizer produced the highest stem diameter, leaf length, leaf width, leaf ratio, and stem ratio (p 0.05) by the level of nitrogen fertilizer. The fresh biomass, dry matter, crude protein, ash, NFE, and TDN production increased significantly (p<0.05) with the increased level of nitrogen fertilizer. Based on those findings, it can be concluded that nitrogen fertilizer application at the level of 50 kg N ha-1 produces better growth, fresh biomass, dry matter, and nutrients production.

Pengaruh Pupuk Hayati Terhadap Pertumbuhan Bibit Kelapa Sawit (Elaeis guineensis Jacq.) pada Pembibitan Awal

This study aims to determine the effectiveness of N2-fixing microbes contained in organic organic fertilizers at four levels of nitrogen fertilizer application in increasing the performance of oil palm seedlings. The experiment was carried out in the form of an experiment using a Randomized Block Design with 2 factors: organic organic fertilizer and nitrogen fertilizer. The first factor with three levels of treatment, namely without organic biological fertilizer, Organic fertilizer from cow dung (Agro Flower) 1 g / kg of Soil and Organic organic fertilizer (Biost) 1 g / kg of Soil. While the second factor consists of four levels, namely without N fertilizer, N fertilizer 50% of the standard dose, N fertilizer 100% of the standard dose, and N fertilizer of 150% of the standard dose. Each treatment was tested on 4 oil palm seedlings and repeated 3 times, so that 144 experimental plants were obtained. The observations made were the variable plant performance includes plant height, number of leaves, and stem diameter. Variants of plant nutrient levels included total N nutrient levels, P nutrient levels, and K nutrient levels. The results showed that N-inhibiting microbes contained in organic organic fertilizer increased plant height and stem diameter significantly in oil palm nurseries. The use of a 100% dose of N fertilizer together with organic biofertilizers shows the best crop performance results.

Effects of Different Level of Nitrogen Fertilizer Application on Growth, Yield, Quality and Storage Life of Onion (Allium cepa L.) at Jimma, South Western Ethiopia

Onion (Allium cepa L.) is one of the most important vegetable crops produced in Ethiopia. Yield and productivity of the crop has been far below the regional and national standards owing to several factors; absence of location specific fertilizer recommendation being the major among others. In Ethiopia, post harvest loss of vegetables contributed up to 30% yield reduction. Thus, a field experiment was conducted at Jimma University College of Agriculture and Veterinary Medicine Research field during dry season to study the effects of Nitrogen fertilizer application on growth, yield, quality and storage life of irrigated onion under Jimma condition, South Western Ethiopia. The treatments consisted of four levels of Nitrogen (0, 50, 100 and 150 kg N ha -1 ) that laid out in Randomized Complete Block Design with three replications. Data on growth, yield, bulb quality and storage life parameters were recorded and analyzed using GenStat 12.1 version computer soft ware packages. Results of the study revealed that; Nitrogen fertilizer applications had shown a highly significant effect on growth, yield and quality of onion. Similarly, the keeping qualities of the Onion bulbs are highly influenced by application of N at different levels. Excessive application of Nitrogen fertilizer caused higher bulb rots (%); bulb sprouts (%) and weight loss (%) during the three month storage time at ambient temperature. This can be recommended for use by potential onion investors or farmers in the study area. Keywords : Growth, Nitrogen, Onion, Quality, Storage life, Yield. DOI : 10.7176/JNSR/9-10-05 Publication date :May 31 st 2019

Performance of Two Rape (Brassica napus) Cultivars under Different Fertilizer Management Levels in the Smallholder Sector of Zimbabwe

Crop response to fertilizer application depends on the physiological and morphological characteristics of the cultivars, thus causing cultivar differences in growth rate and final yield. A study was carried out in the Zvimba smallholder farming area of Zimbabwe, from November 2016 to February 2017, to investigate the performance of two rape (Brassica napus) cultivars under different nitrogen fertilizer management levels. An experiment was set up in a randomized complete block design, replicated three times, with two rape varieties, Hobson and English Giant, and 5 ammonium nitrate (AN) (34.5% N) fertilizer application rates (200 kg/ha, 300 kg/ha, 350 kg/ha, and 400 kg/ha) as factors. Nitrogen fertilizer rates had a significant (p&lt;0.05) effect on leaf length at 6 WAP and 7 WAP. Nitrogen fertilizer application levels had significant effects on both in-season and total fresh leaf yield. There were no varietal effects on the leaf length (p&gt;0.05), in-season yield and total leaf yield (p&gt;0.05), and there were also no variety ∗ fertilizer application level interaction effects on leaf length, in-season yield and total leaf yield (p&gt;0.05). From the results of this study, English Giant rape would maintain a longer leaf length than Hobson up to the end of the season, but the two cultivars have similar yield response to fertilizers’ application rate. Both the English Giant rape and Hobson rape cultivars can, therefore, be recommended for production in the Mhondoro smallholder farming area of Zimbabwe and other areas with similar climatic and soil characteristics.

YIELD AND AGRONOMIC EFFICIENCY OF SUNFLOWER IN RESPONSE TO NITROGEN FERTILIZER APPLICATION AND SOWING SEASON

ABSTRACT Agronomic responses to the use of agricultural inputs have been used in agriculture to identify the optimal level of nutrients to be supplied for high yield. This strategy helps to avoid economic losses and excessive application of fertilizers that has caused pollution of aquifers and soil degradation. The aim of the study was to evaluate water use efficiency, agronomic efficiency of nitrogen, heat units and use of evapotranspiration in yield and its components in sunflowers under hot climate conditions in function of nitrogen fertilizer application during two sowing season. The experiment was conducted in the field. The treatments were two sowing seasons and three levels of nitrogen fertilizer application and one control: 0, 60, 80 and 120 kg N ha-1. The nitrogen source was urea. The experimental design was complete random blocks with factorial array and four replications. The occurrence of cv. Cobalto sunflower phenological stages were not modified by the treatments. Urea favored agronomic efficiency and water use efficiency. Yield components were modified positively, with increasing receptacle area, 100-grain weight, and grain yield per receptacle. Application of nitrogen fertilizer favored sunflower development, although environmental conditions are of critical importance as demonstrated by a clear interaction between the yield response to fertilizer application and the environment where the plants grew.

Low Nitrogen Application Enhances Starch-Metabolizing Enzyme Activity and Improves Accumulation and Translocation of Non-structural Carbohydrates in Rice Stems.

More than 4 billion inhabitants in Asia depend on rice for 35–60% of the calories consumed in their diets, but new rice cultivars frequently do not reach expected yields because of poor rice grain filling. Here, we quantified the activities of enzymes involved in starch metabolization in rice to investigate the mechanisms regulating the accumulation and translocation of stem non-structural carbohydrates (NSC) under different levels of nitrogen fertilizer application. A pot experiment was conducted using two rice cultivars, Liangyoupeijiu (LYPJ) and Shanyou63 (SY63), under high and low nitrogen applications. Compared with high nitrogen application (HN), low nitrogen application (LN) increased stem NSC concentration before the heading stage and NSC translocation during the grain filling stage; concomitantly, LN significantly shortened the active grain filling period and increased the grain filling rate in superior spikelets. Compared with the LYPJ cultivar, SY63 exhibited a higher grain weight, higher grain filling percentage, and higher stem NSC concentration before heading and greater NSC translocation after heading. During the period between panicle initiation and heading, the activities of adenosine diphosphate-glucose pyrophosphorylase (AGP), starch synthase (StS), and starch branching enzyme (SBE), all enzymes involved in starch synthesis, increased under the LN treatment and positively correlated with increases in stem NSC. During grain filling, the activities of enzymes involved in starch-to-sucrose conversion [α-amylase, β-amylase, and sucrose phosphate synthase (SPS)] increased under the LN treatment and positively correlated with stem NSC remobilization. Overall, the investigated enzymes exhibited higher activities in SY63 than in LYPJ. Our results suggest that low nitrogen increases the activities of AGP, StS, SBE, α-amylase, β-amylase, and SPS, leading to increased accumulation and remobilization of stem starch and NSC in SY63. We conclude that calculated reductions in nitrogen application and the choice of an appropriate cultivar may improve rice grain yields via enhanced stem NSC accumulation and translocation, thereby reducing the costs and increasing the sustainability of rice production.