Deep Placement Of Fertilizer Research Articles

Effect of fertilizer deep placement and nitrification inhibitor on N2O, NO, HONO, and NH3 emissions from a maize field in the North China Plain

Fertilized soil is an essential source of atmospheric gaseous nitrogen compounds (GNC, including N2O, NO, HONO, and NH3) that play important roles in global warming and regional air pollution. However, there is still a lack of comprehensive research on the exchange fluxes of these gases between soil and the atmosphere, let alone exploration of mitigation measures. Herein, the fluxes of N2O, NO, HONO, and NH3 under different fertilization treatments (surface fertilization (SF), deep fertilization (DF), DF with added nitrification inhibitor (DN), and control (CK, non-fertilization)) were comparatively investigated by open-top dynamic chambers in a maize field in the North China Plain (NCP) in 2022. The results showed that fertilization significantly promoted soil GNC emissions under SF and DF treatments, while there was no significant increase in GNC emissions except for NH3 under the DN treatment after fertilization. In comparison to the SF treatment, the cumulative emissions under the DF treatment exhibited a significant reduction, amounting to 80.8% for N2O, 89.4% for NO, 88.3% for HONO, 84.8% for NH3, and 83.9% for the total emissions of these four gases. These results emphasize the effect of fertilizer deep placement in mitigating soil GNC emissions, and further reductions were observed when using nitrification inhibitors like dicyandiamide (DCD). Compared with the cumulative emissions under the SF treatment, the DN treatment showed reductions exceeding 95% for N2O, NO, and HONO, and 77.1% for NH3 due to the inhibition of ammonia oxidation by DCD, resulting in an overall reduction of 88.8% for the four gases. Therefore, we advocate deep placement of fertilizer with or without nitrification inhibitors during crop cultivation to achieve a comprehensive reduction in GNC emissions and improve regional air quality.

Differential Effects of Nitrogen and Phosphorus Fertilization Rates and Fertilizer Placement Methods on P Accumulations in Maize.

Crop production in Afghanistan suffers from limited phosphorus (P) availability, which severely hinders national agriculture sustainability. This study hypothesized that deep fertilizer placement could significantly enhance the uptake of immobile P and, thus, tissue P accumulation and crop yield. A two-year pot experiment growing two maize (Zea mays) hybrid cultivars (Xida-789 and Xida-211) was, therefore, conducted to test these hypotheses under three contrasting fertilizer placement methods (broadcast, side band, and deep band). In doing so, P concentrations in both maize tissues and soils were compared at 45, 60, and 115 days after sowing (DAS) under nine combinations of nitrogen (N) and P fertilizer rates (kg ha-1: N112P45, N112P60, N112P75, N150P45, N150P60, N150P75, N187P45, N187P60, N187P75). Results have shown that deep band placement significantly increased P uptake efficiency, leading to greater P concentration and accumulation in maize tissues compared to the other two fertilization methods. This improved P uptake was attributed to several factors associated with deep placement, including reduced P fixation, enhanced root access to P, and moisture availability for P uptake. Additionally, deep band placement combined with higher N application rates (N187 and N150) further enhanced plant P uptake by promoting P availability and utilization mechanisms. Deep band placement also resulted in significantly higher total soil P, Olsen-P, and P use efficiency than broadcast and side band methods, indicating a more efficient P fertilization strategy for maize that can improve growth and yield. This study also found positive correlations between P concentration in plant organs and soil Olsen-P, highlighting the importance of adequate soil P levels for optimal plant growth. Overall, our results have shown that deep band fertilizer placement emerged as a superior strategy for enhancing P uptake efficiency, utilization, and maize productivity compared to broadcast and side band placement. The outcome generated from the deep band fertilization by this greenhouse study can be recommended for field practices to optimize P fertilizer use and improve maize production while minimizing potential environmental P losses associated with broadcast fertilization.

Mechanized Fertilizer Deep Placement: A Transition Towards Climate Smart Agriculture

Mechanized Fertilizer Deep Placement: A Transition Towards Climate Smart Agriculture

Agricultural management practices in China enhance nitrogen sustainability and benefit human health.

The potential of enhanced agricultural management practices to drive sustainability is rarely quantified at grassroots level. Here we analyse nitrogen use and loss in Chinese cropland, drawing from data collected in 2,238,550 sites in two national agricultural pollution source censuses from 2007 to 2017. We find an upswing of 10% in crop yields and an 8% reduction in nitrogen pollution during this period, owing to the promotion and adoption of various management practices (including the combination of organic and chemical fertilizers, straw recycling and deep placement of fertilizer). These practices have collectively contributed to an 18% increase in nitrogen use efficiency in the country. By fully embracing them, we project that annual cropland pollution could be further reduced by up to 1.4 Mt of nitrogen without compromising crop yields. Environmental and human health benefits are projected to consistently outweigh implementation costs in the future, with total benefits reaching US$15 billion.

Effects of Deep Placement of Fertilizer on Growth, Productivity, and Fertilizer Use Efficiency of Rice in Cool Climatic Region

Effects of Deep Placement of Fertilizer on Growth, Productivity, and Fertilizer Use Efficiency of Rice in Cool Climatic Region

Does the Deep Placement of Fertilizers Increase Potato Yields, Fertilization Efficiency and Reduce N2O Emissions from the Soil?

Despite the notable decline in potato cultivation areas across Poland and Europe, potatoes remain a crucial crop with diverse applications. Achieving the ambitious emission targets set by the EU for agricultural production may be easier with the practice of deep placement of slow-release fertilizers, which may increase yields and reduce greenhouse gas emissions. To examine the effect of deep placement of slow-release fertilizers on potato tuber yields, plant nutrient uptake, nutrient use efficiency, and soil N2O-N emissions, a two-year field experiment was conducted on loamy sand soil classified as Alblic Podzol (Ochric) soil, under temperate climate conditions prevailing in central Poland. The experiment involved a three-field rotation (potatoes, wheat, and peas), with potatoes being cultivated after peas in both years of the study. The experiment compared the effects of applying slow-release fertilizer at soil depths of 10 and 20 cm (DP10 and DP20) to fertilization with single-nutrient fertilizers applied to the soil surface (TD). The experiment utilized increasing doses of nitrogen and phosphorus, denoted as D0 (control), D1, D2, and D3, along with a standard dose of potassium across all tested fertilizer application methods. The results of this study confirmed that deep placement of slow-release fertilizers had limited effects on potato tuber yields. Deep placement of slow-release fertilizer increased plant nitrogen uptake by 2.8–13.5% compared to topdressing. Consequently, there was an improvement in nitrogen use efficiency from 29.8–75.0% on sites with fertilizer topdressing to 38.7–89.8% on sites with slow-release fertilizer deep placement. Phosphorus uptake by plants on sites with slow-release fertilizer deep placement was approximately 9.3–13.0% higher than on sites with fertilizer topdressing. This led to an enhancement in phosphorus use efficiency from about 15.1–19.5% on fertilizer topdressing sites to 19.4–25.4% on slow-release fertilizer deep placement sites. The impact of fertilizer deep placement was found to be less pronounced compared to the effects observed with increased nitrogen and phosphorus doses. The most important factors affecting tuber yield and nutrient use in potatoes were rainfall levels during the growing season. Deep fertilization did contribute to reduce soil N2O emissions by about 14%. However, further research involving different fertilization methods is needed to comprehensively assess the effectiveness of this practice in reducing greenhouse gas emissions.

Global meta-analysis and three-year field experiment shows that deep placement of fertilizer can enhance crop productivity and decrease gaseous nitrogen losses

Context or problemThere is an urgent need to address the contradiction between food security and climate change, and achieve the highest crop productivity at the lowest environmental cost. Scientific fertilization is the key to solving this problem. Objective or research questionDeep placement of fertilizer (DPF) is an effective fertilization strategy for improving crop productivity and reducing gaseous N losses, but its effectiveness varies among agricultural systems and appropriate fertilization depths have not yet been determined. MethodsIn this study, we synthesized 99 global studies (120 locations) and conducted a three-year field experiment to evaluate the effects of DPF on the crop yield, nitrogen use efficiency (NUE), and nitrous oxide (N2O), and ammonia (NH3) emissions, and explored their responses to different climates, field management practices, and environmental factors. ResultsDPF could increase the grain yield by 13.5%, and NUE by 33.8%, and reduce N2O emission by 16.2%, and NH3 emissions by 86.6%, respectively. Random forest analysis showed that the fertilization depth and nitrogen application rate were the most important factors that determined the impacts of DPF on the crop yield, NUE, and N2O and NH3 emissions, but their effects also depended on the climate conditions, field management practices, and soil environmental factors. Meta-regression modeling showed that the effects of DPF on the crop yield and NUE increased but then decreased as the fertilizer application depth and nitrogen application rate increased, and the effects on N2O and NH3 emissions tended to increase gradually. The meta-analysis also demonstrated that under DPF, the emission factors for N2O and NH3 decreased by 35.8% and 84.5%, respectively. According to the meta-analysis, the global N2O and NH3 emissions under DPF can be reduced by 0.23 and 5.46 Tg N·year–1 respectively. ConclusionsThe results obtained based on global meta-analysis and a three-year experiment demonstrated that DPF obtained higher grain production with lower environmental costs, and the most suitable fertilization depth was identified as 15–25 cm. Implications or significanceThe results obtained in this study provide valuable insights into food security and environmental costs under effective fertilization management.

The impact of livelihood capitals on farmers’ adoption of climate-smart agriculture practices: Evidence from rice production in the Jianghan Plain, China

As the relationship between climate change and agricultural production increasingly gains attention, the FAO recommends the adoption of climate-smart agriculture practices (CSAPs) to ensure the stable development of agriculture amidst changing climatic conditions. However, the adoption rate of CSAPs remains low and the effects of livelihood capitals have received little attention. Based on the survey data for 916 farmers in the Jianghan Plain of China, this paper adopts a multivariate Probit model to examine the impact of farmers’ livelihood capitals which are measured by an entropy-TOPSIS approach on their adoption of CSAPs. Our results demonstrate that different livelihood capitals exert various influence on the adoption of CSAPs. Specifically, human, financial, physical, and social capital have positive relationships with pesticide-oriented CSAPs such as integrated pest management (IPM). Natural capital has a positive relationship with seed- and water- oriented CSAPs like tolerant rice varieties (TRV). Natural capital positively relates to soil-oriented CPSPs including rice straw mulching (RSM) while physical capital has a negative effect. Natural and physical capitals have positive relationships with fertilizer-oriented CSAPs like deep placement of fertilizer (DPF). Social and natural capitals have positive relationships with soil-oriented CSAPs such as no-tillage direct seeding (NTDS) while financial capital has a negative effect. Climate factors are also important in the adoption of CSAPs such as TRV and RSM. Finally, policy recommendations are suggested to enhance household livelihood capitals to promote the adoption of each type of CSAP.

Anomalous increase in global atmospheric ammonia during COVID-19 lockdown: Need policies to curb agricultural emissions

The restrictions imposed on human activities during the COVID-19 lockdown (LD) period provided a new scenario to identify potential sources of atmospheric pollution. There are several studies that deal with changes in air quality around the world during LD, but very few on atmospheric ammonia (NH3). Therefore, we examine the changes in global NH3 during LD (April–May 2020) in comparison to the pre-lockdown (PreLD, April–May 2017–2019) and post-lockdown (PostLD, April–May 2021) periods, and assess the factors responsible for these changes. We observe an increase in NH3 during LD across the latitudes, with very high values in the western Europe, Eastern China (EC), the Indian subcontinent and the eastern United States of America (USA). However, a decline in NH3 is observed in some regions of South America (SA) and North America (NA). Similar changes in NH3 during LD are also observed in smaller spatial scales, as found in 3000 cities across the globe. The reduction of sulphur dioxide (SO2), nitrogen dioxide (NO2), nitric acid (HNO3), humidity and cloud cover as a result of restrictions on human activities, particularly in the western Europe and the USA, may have impeded the conversion of NH3 to particulates, which led to a higher NH3 there. Nevertheless, agricultural activities and livestock are the most prominent sources of atmospheric NH3, and were not under restriction during LD, show an enhancement in terms of the use of nitrogen fertilizer, crop production and area harvested, which also cause a rise in NH3 in these regions. Therefore, it is evident that the changes in meteorology and atmospheric composition, together with increased agricultural activities, led to the global increase in atmospheric NH3 during LD. That is, most pollutants show a decline during LD, but NH3 exhibits a rise due to its sources such as agricultural activities. Henceforth, environmental regulations, policies and advanced technologies are required in the agricultural sector, such as fertilizer deep placement using urea briquettes and restricted application of nitrogen fertilizers, to curb NH3 emissions.

Slow-release fertilizer deep placement increased rice yield and reduced the ecological and environmental impact in Southeast China: A life-cycle perspective

An unreasonable application of nitrogen fertilizer leads to increased agricultural greenhouse gas (GHG) emissions and carbon footprint (CF). To solve this issue, slow-release fertilizer and deep placement of nitrogen fertilizer are recommended, and have been proven effective in improving nitrogen utilization efficiency and reducing nitrogen loss. However, the deep placement of fertilizer increases the cost of mechanical fuel and labor, especially in the hilly and mountainous areas of southeast China and the comprehensive effects throughout the life cycle of crop production, including economic benefits, energy flow, and environmental and ecological advantages, resulting from different application strategies for nitrogen fertilizer, are still largely unknown. In this work, a two-year field trial was conducted in Fujian Province, China, from 2021 to 2022. The main objectives of the study were to investigate the yield and GHG emissions resulting from the deep placement of slow-release fertilizer (DSK) and to assess the carbon footprint, energy use efficiency, and net economic and ecological benefits from a life-cycle perspective. The results showed that compared with deep placement of urea (DCK), slow-release fertilizer broadcasting (SK), and the traditional fertilization mode practiced by farmers (CK), the average annual yield of rice under DSK treatment significantly increased by 8.78%, 15.18%, and 23.54% respectively. Compared with CK, the contents of indole-3-acetic acid (IAA) and trans-Zeatin Riboside (t-ZR) under DSK were significantly increased and the dry matter translocation amount, Non-Structural Carbohydrates (NSC) translocation amount and Nitrogen translocation amount were significantly increased by 22.79%, 49.60% and 41.47% respectively. GHG emissions were indirectly reduced by the transport of above-ground substances to grains. The average cumulative CH4 emissions were significantly reduced by 25.34% in the DSK treatment, compared to the CK treatment, primarily as a result of decreased methanogenic gene abundance of mcra gene. Additionally, N2O emissions decreased significantly by 48.97%, compared to the CK, mainly due to a decrease in nirK gene abundance and an increase in nosZ gene abundance in denitrifying bacteria. Furthermore, the carbon footprint of the DSK treatment significantly decreased by 38.74% compared to the CK treatment, while net energy income and net ecological and economic benefits increased by 43.83% and 76.43%, respectively. Comprehensive analysis showed that deep placement of slow-release fertilizer is a sustainable nitrogen fertilizer management mode that helps to balance grain yield, environmental footprint, and economic benefits in southeast China.

Repositioning fertilizer manufacturing subsidies for improving food security and reducing greenhouse gas emissions in China

China removed fertilizer manufacturing subsidies from 2015 to 2018 to bolster market-oriented reforms and foster environmentally sustainable practices. However, the impact of this policy reform on food security and the environment remains inadequately evaluated. Moreover, although green and low-carbon technologies offer environmental advantages, their widespread adoption is hindered by prohibitively high costs. This study analyzes the impact of removing fertilizer manufacturing subsidies and explores the potential feasibility of redirecting fertilizer manufacturing subsidies to invest in the diffusion of these technologies. Utilizing the China Agricultural University Agri-food Systems model, we analyzed the potential for achieving mutually beneficial outcomes regarding food security and environmental sustainability. The findings indicate that removing fertilizer manufacturing subsidies has reduced greenhouse gas (GHG) emissions from agricultural activities by 3.88 million metric tons, with minimal impact on food production. Redirecting fertilizer manufacturing subsidies to invest in green and low-carbon technologies, including slow and controlled-release fertilizer, organic–inorganic compound fertilizers, and machine deep placement of fertilizer, emerges as a strategy to concurrently curtail GHG emissions, ensure food security, and secure robust economic returns. Finally, we propose a comprehensive set of government interventions, including subsidies, field guidance, and improved extension systems, to promote the widespread adoption of these technologies.

Effects of integrated plant nutrition systems with fertilizer deep placement on rice yields and nitrogen use efficiency under different irrigation regimes

Improved fertilizer management, with a combination of organic and inorganic inputs, has the potential to enhance rice yield while maintaining soil health. However, studies on the effects of broadcast prilled urea (PU) and urea deep placement (UDP) applied in combination with organic inputs (poultry litter [PL] and vermicompost [VC]), as integrated plant nutrition systems (IPNSs), on rice yields and nitrogen use efficiency (NUE) under alternate wetting and drying (AWD) irrigation are limited. We conducted field experiments during the dry and wet seasons of 2018, 2019, and 2020 to investigate the effects of fertilizer treatments, including control (no nitrogen), UDP, PU, and IPNSs (PU + VC, PU + PL, and UDP + PL) on rice yield and NUE under two irrigation regimes – AWD and continuous flooding (CF). The results revealed that fertilizer treatment and irrigation regime had significant (p < 0.05) interaction effects on rice yield and the agronomic efficiency of N (AEN) during the dry season. UDP significantly (p < 0.05) boosted rice yield, total dry matter (TDM), and NUE as compared to broadcast PU in both wet and dry seasons. Similarly, the IPNS treatment of UDP with PL significantly (p < 0.05) boosted rice yield, TDM, and NUE in comparison to broadcast PU. Under AWD irrigation, UDP alone produced higher rice yields than other treatments, while UDP, and UDP with PL produced similar yields under CF irrigation. During the dry season, AWD irrigation significantly (p < 0.05) increased rice yield, TDM, and AEN when compared to CF conditions, but during the wet season, AWD irrigation demonstrated a rice yield and NUE equivalent to CF. This research implies that using a UDP alone or in combination with PL as an IPNS could be a good way to boost crop productivity while also maintaining soil fertility.

Advantages of deep fertilizer placement in environmental footprints and net ecosystem economic benefits under the variation of precipitation year types from winter wheat fields

Advantages of deep fertilizer placement in environmental footprints and net ecosystem economic benefits under the variation of precipitation year types from winter wheat fields

Ammonia mitigation campaign with smallholder farmers improves air quality while ensuring high cereal production.

Reducing cropland ammonia (NH3) emissions while improving air quality and food supply is a challenge, particularly in China where there are millions of smallholder farmers. We tested the effectiveness of a tailored nitrogen (N) management strategy applied to wheat-maize cropping systems in 'demonstration squares' across Quzhou County in the North China Plain. The N-management techniques included optimal N rates, deep fertilizer placement and application of urease inhibitors, implemented through cooperation between government, researchers, businesses and smallholders. Compared with conventional local smallholder practice, our NH3 mitigation campaign reduced NH3 volatilization from wheat and maize by 49% and 39%, and increased N-use efficiency by 28% and 40% and farmers' profitability by 25% and 19%, respectively, with no detriment to crop yields. County-wide atmospheric NH3 and fine particulate matter (with aerodynamic diameter <2.5 μm) concentrations decreased by 40% and 8%, respectively. County-wide net benefits were estimated at US$7.0 million. Our demonstration-square approach shows that cropland NH3 mitigation and improved air quality and farm profitability can be achieved simultaneously by coordinated actions at the county level.

Deep placement of fertilizer enhances mineral uptake through changes in the root system architecture in rice

Deep placement of fertilizer enhances mineral uptake through changes in the root system architecture in rice

Effect of Deep Placement Fertilization on the Distribution of Biomass, Nutrients, and Root System Development in Potato Plants.

The study was carried out in designed pots-rhizoboxes. Root systems were evaluated using computer scanning to determine total length, root area, and root diameter. The study showed a favorable effect of deep placement of fertilizers on total yield, increasing biomass yield by 7-17% relative to surface fertilization. The largest biomass increase under the influence of deep fertilization was obtained in the case of tuber yield, in which a yield increase of 18-34% was obtained. Higher yields of potato tubers were obtained under depth fertilization compared to surface application of fertilizers. Under the influence of deep fertilization at a depth of 20 cm, the uptake of nitrogen and phosphorus by potato biomass increased by 20-21%. Increased depth of fertilization increased the proportion of nitrogen accumulated in the tubers, while in the case of phosphorus, no effect of depth on P distribution was shown. An analysis of root system parameters showed a positive effect on increases in length and total root area under deep fertilization of potato plants. Based on the study, it was found that the distribution of dry matter, nutrients, and potato root development parameters were most optimal when fertilizer granules were applied at a depth of 20 cm.

신개발 심층시비장치를 이용한 심층시비의 밭작물 재배 효과

Understanding the Effects of Deep Fertilization on Upland Crop Cultivation and Ammonia Emissions using a Newly Developed Deep Fertilization Device-Ammonia (NH₃),Fertilizer deep placement,Nitrogen,Upland crop,Yield

Efficacy of Mechanical Seedling Transplanter and Deep Placement of Mixed Fertilizer on Rice Yield

A field experiment was conducted at the West Byde of BRRI farm, Gazipur during T. Aman and Boro, 2021-22 season to evaluate the efficacy of newly developed mechanical rice transplanter cum fertilizer applicator. Five treatments in Randomized Complete Block Design with three replications. Field experiments was conducted on silty clay loam soil in Gazipur. Individual plot size was 8m×5m with 30 cm buffer zone. The treatments were T1 = Mechanical transplanting along with 100% fertilizer (Urea, TSP, MoP and Gypsum) deep placement, T2 = Mechanical transplanting along with 80% fertilizer (80% Urea and 100% TSP, MoP and Gypsum) deep placement, T3 = Mechanical transplanting along with 70% fertilizer (70% urea and 100% TSP, MoP and Gypsum) deep placement, T4 = Mechanical transplanting along with 100% fertilizer hand broadcasting (TSP, MoP and Gypsum fertilizer as basal dose and urea fertilizer in three split) and T5 = Hand transplanting of same seedling of rice transplanter along with 100% fertilizer hand broadcasting (TSP, MoP and Gypsum in basal dose and urea fertilizer in three split) and T6 = BRRI recommended practice. In this experiment, BRRI dhan89 and BRRI dhan92 was used in T. Aman and Boro seasons, respectively. In the field, saving percentage of urea fertilizer varied from 25% to 28% against the calibration of 30% of urea saving due to the variation of the machine, operational speed and more penetration of the driving wheel during operation. It was found that grain yield was varied with the mode and rate of urea fertilizer application. Mechanical transplanting along with urea fertilizer deep placement (80% of recommended dose) gave significantly higher yield compared to manual transplanting and hand broadcasting of urea. Mechanical transplanting along with deep placement of urea fertilizer is a promising technology for rice farmers in Bangladesh. Manual transplanting is tedious and time consuming as a result mechanical transplanting is seen as a solution of labor problems. No significant differences among the treatments was found in growth parameters. Significant variations were recorded in case of yield. BRRI recommended practice and mechanical transplanting with 80% urea with other fertilizers were produced very similar grain yield. From these results, it might be said that mechanical transplanting with 80% urea fertilizer is recommended with BRRI recommended hand transplanting practice. Urea saving is additional benefit with time savings and low transplanting cost when transplanted with rice transplanter cum fertilizer applicator.

Influence of Reduced Tillage, Fertilizer Placement, and Soil Afforestation on CO2 Emission from Arable Sandy Soils

Extreme meteorological phenomena resulting from climate change caused by anthropogenic emissions of greenhouse gases (GHG) require the implementation of CO2 mitigation practices from various industries, including agriculture. Owing to varying soil, climatic, and agrotechnical characteristics, they may have different efficiencies in mitigating soil CO2 emissions. The aim of this study was to evaluate the impact of three mitigation practices (reduced tillage, deep fertilizer placement, and soil afforestation) on CO2 emissions from sandy soils in Central and Eastern Europe allowing the prediction of the mitigation effectiveness of these methods. The average soil CO2-C flux under a moldboard plow system ranged from 218.4 ± 108.4 to 263.7 ± 176.6 mg CO2-C m−2 h−1 and under a reduced tillage system ranged from 169.7 ± 118.7 to 163.6 ± 115.2 mg CO2-C m−2 h−1 in a year with normal meteorological conditions and under extreme drought conditions, respectively. In the dry growing season, similar amounts of CO2-C were released from the soil fertilized to the soil surface and after mineral fertilizers application at a depth of 10 cm and 20 cm (133.7 ± 155.8, 132.0 ± 147.5 and 131.0 ± 148.1 mg CO2-C m−2 h−1, respectively). Meanwhile, from the forest soil, the average CO2-C emission in the dry growing season was 123.3 ± 79 mg CO2-C m−2 h−1. The obtained results revealed that reduced tillage on sandy soil allowed for reduced CO2 emissions from the soil by 28.7–61.2% in normal and drought weather, respectively. Under drought conditions, deep fertilizer placement did not reduce CO2 emissions from sandy soil, and CO2 emissions from forest soils were even higher than from arable soils.

Mechanized Hybrid Rice Seed Production: Planting Density, the Flight Height of an Unmanned Aerial Vehicle, Fertilizer Application, and the Row-Ratio of Parents

The mechanized seed production of hybrid rice (Oryza sativa L.) represents significant progress in modern agriculture. However, the technologies and the crop management strategies in mechanized hybrid rice seed production are still immature. The present study was conducted with three field experiments to explore the effects of different planting densities, the flight height of an agricultural unmanned aerial vehicle (AUAV) for assisting the pollination, fertilization techniques, and the row-ratio of the restore line and the sterile line on seed yield in hybrid rice seed production. In experiment 1, three planting densities “DS1: 250000 hills per ha; DS2: 285000 hills per ha; DS3: 3,33,000 hills per ha” and three flight heights of an AUAV (FH1: above ground 2 m; FH2: above ground 3 m; FH3: above ground 4 m) were adopted. The results showed that DS1 and DS2 treatments produced a higher seed yield than the DS3 treatment, and the seed yield in the FH2 treatment was significantly higher than FH1 and FH3. In experiment 2, two fertilizer application methods, mechanized deep placement of fertilizer and traditional manual broadcasted fertilizer, were adopted. The results showed that deep placement of fertilizer significantly increased seed yield by increasing the effective panicle number and the grain number per panicle. In experiment 3, three row-ratios of sterile line and restore line at 8:1 (R1), 9:1 (R2), 10:1(R3) were adopted, and the highest seed yield was recorded in the R1 treatment.