Application Of Slow-release Fertilizer Research Articles

Humic Acid-Functionalized Lignin-Based Coatings Regulate Nutrient Release and Promote Wheat Productivity and Grain Quality.

The rational application of fertilizers is crucial for achieving high crop yields and ensuring global food security. The use of biopolymers for slow-release fertilizers (SRFs) development has emerged as a game-changer and environmentally sustainable pathway to enhance crop yields by optimizing plant growth phases. Herein, with a renewed focus on circular bioeconomy, a novel functionalized lignin-based coating material (FLGe) was developed for the sustained release of nutrients. This innovative approach involved the extraction and sustainable functionalization of lignin through a solvent-free esterification reaction with humic acid─an organic compound widely recognized for its biostimulant properties in agriculture. The primary objective was to fortify the hydration barrier of lignin by reducing the number of its free hydroxyl groups, thereby enhancing release control, while simultaneously harnessing the agronomic benefits offered by humic acid. After confirming the synthesis of functionalized lignin (FLGe) through 13C NMR analysis, it was integrated at varying proportions into either a cellulosic or starch matrix. This resulted in the creation of five distinct formulations, which were then utilized as coatings for diammonium phosphate (DAP) fertilizer. Experimental findings revealed an improved morphology and hardness (almost 3-fold) of DAP fertilizer granules after coating along with a positive impact on the soil's water retention capacity (7%). Nutrient leaching in soil was monitored for 100 days and a substantial reduction of nutrients leaching up to 80% was successfully achieved using coated DAP fertilizer. Furthermore, to get a fuller picture of their efficiency, a pot trial was performed using two different soil textures and demonstrated that the application of FLGe-based SRFs significantly enhanced the physiological and agronomic parameters of wheat, including leaf evolution and root architecture, resulting in an almost 50% increase in grain yield and improved quality. The results proved the potential of lignin functionalization to advance agricultural sustainability and foster a robust bioeconomy aligning with the premise "from the soil to the soil".

Slow-release Fertilizer Application on Silk (Falcataria moluccana Miq.) and Rice (Oryza sativa L.) Plant Growth and Yield in Agroforestry System

The aim of this experiment is to evaluate the impact of chitosan-NPK slow-release fertilizer (CS-NPK SRF) on the germination and growth of silk tree and rice in different planting patterns, as well as to assess the nutrient release rate of the SRF. The germination test followed a complete randomized design, incorporating a single factor (fertilizer type), namely no fertilizer (F0), SRF CS 0.5% weight 0.03 g (F1), SRF CS 0.5% 0.01 g (F2), SRF CS 0.7% 0.03 g (F3), SRF CS 0.7% 0.01 g (F4), and conventional NPK fertilizer (F5). The growth test utilized a 2-factor split-plot design, with the primary factor being the planting pattern (sengon/rice monoculture-SM/RM and sengon-rice agroforestry-AF) and the second factor being the fertilizer type. Results indicate that F2 and F4 yielded the highest germination and growth values in both plants, although not significantly different from F0. These findings suggest that CS-NPK SRF has the potential to enhance plant growth. The AF pattern exhibited lower growth compared to SM/RM, attributed to plant competition. CS-NPK SRF demonstrated a slower nutrient release (47.65% N; 85.01% P; 31.80% K) compared to conventional fertilizers. This slow release could potentially reduce nutrient loss to the environment while enhancing plant nutrient absorption.

Morphological Character and Clorophyl Content Index of Corn Infected with Dowry Disease on Land Applied With Slow Realease Fertilizer Based on Corn Cob Biochar

Downy mildew is a significant disease of corn plants caused by the pathogenic fungus Peronosclerospora maydis, with attack rates reaching 95%. The application of slow-release fertilizer based on corn cob biochar is expected to increase the resistance of corn plants. Similarly, Bacillus sp. and Pseudomonas sp. are known as antagonistic microorganisms. Bacteria can produce antibiotic compounds that hydrolyze fungal cell walls, siderophores, and other antibiotic properties that inhibit pathogen growth. This study aims to determine the morphological characteristics of downy mildew-infected corn on biochar-applied land. Treatments were arranged factorially in a Factorial Randomized Block Design repeated four times. The treatment was the application of slow-release fertilizer from biochar mixed with NPK fertilizer, namely control, slow-release fertilizer, slow-release fertilizer + cow urine, and slow-release fertilizer + cow urine + bacteria (Azobacter and Bacillus). The results showed that slow-release fertilizer gave the best growth to both normal and downy mildew-affected maize plants. The stomata of typical corn leaves were more open with regular vascular bundles, while those affected by downy mildew had more closed and irregular stomata. The chlorophyll content index in downy mildew-affected maize can also improve by applying biochar-based slow-release fertilizer.

Using slow-release fertilizers ensures the maintenance of litchi (Litchi chinensis Sonn.) production by enhancing soil nutrient supply and optimizing microbial communities

High temperatures and rainy climate conditions result in a very low nutrient utilization rate during crop cultivation in tropical regions. To determine whether slow-release fertilizers could have a positive impact on the yield and quality of litchi, and the soil ecology of orchards while reducing chemical fertilizer application, a field plot experiment with two fertilizer types (chemical fertilizers and lignin-based slow-release fertilizers) combined with a 0 %, 15 % and 30 % reduction of fertilizer application rates was set up from 2018 to 2019. Subsequently, a demonstration trial with an optimum dose of slow-release fertilizers with chemical fertilizers was carried out from 2019 to 2020 in acidic soils. The results demonstrated that all treatments could maintain the yield of litchi between 11,825–13,056 kg/hm2 in 2018–2019. Furthermore, compared to conventional chemical fertilizer treatment, the treatment of lignin-based slow-release fertilizer application with a 15 % fertilizer reduction significantly reduced the concentration of alkaline nitrogen by 19.9 % and available phosphorus by 22.0 % at the 20–40 cm soil layer during the maturity period of litchi growth. The result of the demonstration trial in 2019–2020 further confirmed that a slow-release fertilizer, along with a 25 % reduction in fertilizer application, could maintain high levels of soil alkaline nitrogen and available potassium at the 0–20 cm soil layer without affecting soil bulk density, total soil porosity, and soil aeration. Moreover, the treatment of lignin-based slow-release fertilizer application with a 15 % fertilizer reduction significantly increased the relative abundance of Proteobacteria (1.21 times) and decreased the abundance of Firmicutes (0.81 times) compared to conventional fertilization treatment at the 0–20 cm soil layer. In contrast, it decreased the relative abundance of Firmicutes (0.67 times) and Proteobacteria (0.37 times) at the 20–40 cm soil layer. Meanwhile, the fertilizer application only affected the soil fungi richness but did not increase their diversity. Applying slow-release fertilizers can realize the goal of reducing chemical fertilizers and ensuring excellent litchi production in tropical acidic soils.

Syntheses and Characterization of Cephalexin-Chitosan/Natural Rubber network polymer for Slow-Release Fertilizer.

The increase in the world's population has forced the agricultural sector to increase the production of crops to meet food needs. The spread of nutrient deficiencies in the soil led to economic losses, a reduction in nutritional quality, and total grain quantity for humans and livestock. Coating fertilizers with polymers is one of the most important and effective aspects of slow-release fertilizers in the soil. aim this study, the reaction between chitosan and expired cephalexin as a grafted polymer was done and vulcanized with natural rubber in the presence of tetra methyl thiuram disulfide as catalyst to cover the urea fertilizer. The grafted polymer (chitosan/expired cephalexin compound) was prepared by the Schiff base method. The expired medicinal compound of cephalexin is rich in carbon, nitrogen, sulfur, and hydrogen atoms which improved the diffusion of the fertilizer .So the reaction of the validity of the reaction between chitosan and expired Cephalexin was confirmed by infrared (IR) and it was confirmed the presence of new absorption band due to the Azomethine group. The swelling, water retention, slow release of urea, and biodegradation of the NR/chitosan/expired cephalexin compounds were characterized. The rheometer test was carried out under the pressure of 250 bar and temperature of 170°C, The results showed that the Slow release of urea was increased with the increase in the concentration of cephalexin. The highest release percentage in soil media was 2.67 g/l for the C2 blend. The highest swelling ratio was 189.49 % for the C4 blend while the highest water retention was 75.67% for the C2 blend. It was also shown a good biodegradability, where the highest concentration of cephalexin with chitosan gave the highest rate of biodegradation to be 14.61% for C4. The homogeneity of the blends was studied by FE-SEM. It was concluded that the C1-C4 blends were the best for slow-release fertilizer application.

A facile strategy to fabricate lignocellulose-based slow-release fertilizers via a high-performance treatment of rice straw using deep eutectic solvents

Lignin-based slow-release fertilizers (SRFs) have attracted widespread attention due to their ability to enhance nutrient utilization efficiency and reduce environmental pollution in agricultural production. However, the extraction and separation processes of lignin from biomass sources are intricate, involving substantial quantities of non-reusable toxic reagents. Here, a sustainable and eco-friendly approach using deep eutectic solvents (DES) was employed to treat rice straw, effectively dissolving the lignin present. Subsequently, the in-situ lignin regeneration was facilitated through the addition of a zinc chloride solution. The regenerated lignin was tightly wrapped around and connected to cellulose micro/nanofibers, forming a homogeneous slurry. A simple coating technique was employed to uniformly coat urea particles with the lignocellulosic slurry, yielding lignocellulose-based SRFs. Results revealed that the nutrient release of the lignocellulose-based coated fertilizers in water exceeded 56 days. A pot trial demonstrated that the application of lignocellulose-based SRFs significantly promoted the growth of rice and improved grain yield (by 10.7 %) and nitrogen use efficiency (by 34.4 %) compared to the urea treatment in rice production. Furthermore, the DES demonstrated consistently high efficiency in biomass processing even after four cycles of reuse. This green strategy offers a novel approach for the preparation of SRFs coating materials, promoting agricultural sustainability.

Effect of Chitosan-PMAA-Nutrients Slow-release Fertilizer on Germination of Falcataria moluccana (Miq.) Barneby & J. W. Grimes

Slow-release fertilizer (SRF) with chitosan (CS) coating as a supply of plant nutrients is an alternative to the efficient use of conventional chemical fertilizers and reduces environmental pollution. However, its potential in woody plants is limited. This study aimed to analyze the effect of SRF on Falcataria moluccana germination and SRF phosphorus release rate. This study used SRF from polymerizing CS with methacrylic acid (MAA) to trap nutrients (CS-PMAA-nutrients SRF). The seeds of F. moluccana were germinated at six concentrations SRF: without fertilizer (F0), SRF CS dose 0.5% weight 0.03 g (F1), SRF CS 0.5% 0.01 g (F2), SRF CS 0.7% 0.03 g (F3), SRF CS 0.7% 0.01 g (F4), and conventional fertilizer (F5) for 21 days. SRF can increase the germination of F. moluccana. F4 increased normal sprout (10%) and germination power (16%) of F. moluccana. Furthermore, SRF with a concentration of 0.01 g produced a higher germination value than a concentration of 0.03 g. The release rate of SRF’s nutrients was slower (91.80% phosphorus) than conventional fertilizers. SRF application can reduce nutrients lost and increase the efficiency of nutrient absorption. Hence, it can improve F. moluccana growth.

Effects of a Novel Weeding and Fertilization Scheme on Yield and Quality of Rice

This study aimed to assess the feasibility of a novel weeding and fertilization scheme, namely, mechanical weeding plus a one-time deep application of a reduced amount of slow-release fertilizer for rice cultivation. The effects of the weeding and fertilization method on rice yield and quality were investigated using a split plot test as the research method. Two weeding methods, namely, chemical weeding (CW) and mechanical weeding (MW), and four fertilization methods were tested, including the conventional fertilization method (quantitative split broadcast application of fast-release N fertilizer (CK)), the quantitative split broadcast application of 80% fast-release N fertilizer (LCK), the one-time base application of slow-release fertilizer (SR), and the one-time deep application of 80% slow-release fertilizer (LSR). The results showed that the rice yield under MW with LSR treatment can maintain a high level—higher than 9.2 t ha−1 per year. This was attributed to the slow-release fertilizer and deep fertilization, which increased the number of stems and tillers in the pre-fertility and spike rate, respectively, resulting in a high panicle number with a 20% reduction of N fertilizer. Furthermore, mechanical weeding improved the seed-setting rate, resulting in a higher number of grains per panicle, a higher panicle number, and an increased thousand-grain weight, thereby maintaining a high yield. At the same time, the quality of rice under MW with LSR treatment improved, specifically reflected in the significant improvement of the processing and appearance quality of rice, a slight increase in protein content, and a reduction in the amylose content, thereby improving its nutritional quality while maintaining good cooking quality.

Enhancing maize yield in a conservation agriculture-based maize (Zea mays)- wheat (Triticum aestivum) system through efficient nitrogen management

This study evaluated the impact of contrasting tillage and nitrogen management options on the growth, yield attributes, and yield of maize (Zea mays L.) in a conservation agriculture (CA)-based maize-wheat (Triticum aestivum L.) system. The field experiment was conducted during the rainy (kharif) seasons of 2020 and 2021 at the research farm of ICAR-Indian Agricultural Research Institute (IARI), New Delhi. The experiment was conducted in a split plot design with three tillage practices [conventional tillage with residue (CT), zero tillage with residue (ZT) and permanent beds with residue (PB)] as main plot treatments and in sub-plots five nitrogen management options [Control (without N fertilization), recommended dose of N @150 kg N/ha, Green Seeker-GS based application of split applied N, N applied as basal through urea super granules-USG + GS based application and 100% basal application of slow release fertilizer (SRF) @150 kg N/ha] with three replications. Results showed that both tillage and nitrogen management options had a significant impact on maize growth, yield attributes, and yield in both seasons. However, time to anthesis and physiological maturity were not significantly affected. Yield attributes were highest in the permanent beds and zero tillage plots, with similar numbers of grains per cob (486.1 and 468.6). The highest leaf area index (LAI) at 60 DAP was observed in PB (5.79), followed by ZT(5.68) and the lowest was recorded in CT (5.25) plots. The highest grain yield (2-year mean basis) was recorded with permanent beds plots (5516 kg/ha), while the lowestwas observed with conventional tillage (4931 kg/ha). Therefore, the study highlights the importance of CA practices for improving maize growth and yield, and suggests that farmers can achieve better results through the adoption of CA-based permanent beds and use of USG as nitrogen management option.

Effects of Slow-Release Fertilizer on Lotus Rhizome Yield and Starch Quality under Different Fertilization Periods

Slow-release fertilizer is an environmentally friendly fertilizer that is widely used in crop cultivation instead of traditional nitrogen fertilizer. However, the optimal application time of slow-release fertilizer and its effect on starch accumulation and rhizome quality of lotus remains unclear. In this study, two slow-release fertilizer applications (sulfur-coated compound fertilizer, SCU, and resin-coated urea, RCU) were fertilized under three fertilization periods (the erect leaf stage, SCU1 and RCU1; the erect leaf completely covering the water stage, SCU2 and RCU2; and the swelling stage of lotus rhizomes, SCU3 and RCU3) to study the effects of different application periods. Compared with CK (0 kg∙ha-1 nitrogen fertilizer), leaf relative chlorophyll content (SPAD) and net photosynthetic rate (Pn) remained at higher levels under SCU1 and RCU1. Further studies showed that SCU1 and RCU1 increased yield, amylose content, amylopectin and total starch, and the number of starch particles in lotus, and also significantly reduced peak viscosity, final viscosity and setback viscosity of lotus rhizome starch. To account for these changes, we measured the activity of key enzymes in starch synthesis and the relative expression levels of related genes. Through analysis, we found that these parameters increased significantly under SCU and RCU treatment, especially under SCU1 and RCU1 treatment. The results of this study showed that the one-time application at the erect leaf stage (SCU1 and RCU1) could improve the physicochemical properties of starch by regulating the key enzymes and related genes of starch synthesis, thus improving the nutritional quality of lotus rhizome. These results provide a technical choice for the one-time application of slow-release fertilizer in lotus rhizome production and cultivation.

Optimization of slow-release fertilizer application improves lotus rhizome quality by affecting the physicochemical properties of starch

To achieve the dual goals of high yield and good quality with low environmental costs, slow-release fertilizer (SRF) has been widely used in lotus cultivation as new type of fertilizer instead of traditional nitrogen fertilizer. However, the optimal amount of SRF and how it would promote lotus rhizome quality remain unclear. This study was designed to investigate the photosynthetic characteristics and the synthesis, accumulation, and physicochemical properties of lotus rhizome starches under six SRF levels (CK, S1, S2, S3, S4, and S5). Compared with CK (0 kg ha–1), the net photosynthetic rate (Pn) and SPAD values of leaves remained at higher levels under SRF treatment. Further research showed that SRF increased the lotus rhizome yield, the contents of amylose, amylopectin, and total starch, and the number of starch granules. Among the six SRF levels, S3 (1 035 kg ha–1) showed the greatest difference from CK and produced the highest levels. With the increasing SRF levels, the peak, hot and final viscosities decreased at first and then increased, but the setback viscosity and pasting temperature increased. In order to interpret these changes at the molecular level, the activities of key enzymes and relative expression levels of starch accumulation related genes were analyzed. Each of these parameters also increased under SRF treatment, especially under the S3 treatment. The results of this study show that SRF, especially S3 (1 035 kg ha–1), is a suitable fertilizer option for lotus planting which can improve lotus rhizome quality by affecting starch accumulations related enzymes and genes. These results will be useful for SRF application to high-quality lotus rhizome production with low environmental costs.

Starch Physicochemical Properties of Normal Maize under Different Fertilization Modes

Improving the quality with desired functions of natural starch through agronomic practice will meet the increasing need of people for natural, functional foods. A one-off application of slow-release fertilizer is a simple and efficient practice in maize production, though its influence on the starch quality is scarce. In the present study, the structural and functional properties of the starch of normal maize under two fertilization modes (one-off application of slow-release fertilizer at the sowing time (SF), and three applications of conventional fertilizer at the sowing time, and topdressing at the jointing and flowering stages (CF)) under the same fertilization level (N/P2O5/K2O = 405/135/135 kg/ha) were studied using Jiangyu877 (JY877) and Suyu30 (SY30) as materials. The observed results indicate that the size of starch granules was enlarged by fertilization and the size was the largest under CF in both hybrids. The amylose content was unaffected by CF and reduced by SF in both hybrids. In comparison to no fertilizer (0F), the peak 1/peak 2 ratio was decreased by CF in both hybrids, whereas the ratio under SF was unaffected in JY877 and decreased in SY30. The amylopectin average chain-length was reduced by fertilization and the reduction was higher under CF in JY877. The relative crystallinity was increased by CF in both hybrids and the value under SF was unaffected in SY30 and increased in JY877. The peak, trough, and final viscosities of starch were increased by fertilization in both hybrids. The starch thermal characteristics in response to fertilization modes were dependent on hybrids. The retrogradation enthalpy and percentage were increased by CF in both hybrids, whereas those two parameters under SF were increased in SY30 and decreased in JY877. In conclusion, starch with similar granule size, higher peak 1/peak 2 ratio, and lower relative crystallinity was obtained under SF than under CF for both hybrids. Longer amylopectin chain-length was observed in JY877, which induced lower pasting viscosities in SY30 and lower retrogradation characteristics in JY877.

Risk assessment of Artemia egg shell-Mg-P composites as a slow-release phosphorus fertilizer during its formation and application in typical heavy metals contaminated environment

Artemia egg shell loaded with nano-magnesium (shell-Mg) can be used to recover phosphorus from wastewater. The exhausted Artemia egg shell-Mg (denoted as shell-Mg-P) can be used as a slow-release fertilizer for phosphorus reuse. However, due to the coexistence of heavy metal ions in the environment, the application of slow-release fertilizer for phosphorus removal and reuse may have potential risks. In this paper, the potential risks of Pb2+, Cd2+, Zn2+ and Cu2+ in phosphorus wastewater and soil were studied from the formation and application process of shell-Mg-P. The result showed that shell-Mg adsorbed Pb2+, Cd2+, Zn2+ and Cu2+ in phosphate wastewater during the formation of shell-Mg-P and became shell-Mg-P-metal hybrid biomaterial. Although the experiment proved that the existence of heavy metal ions did not affect the phosphorus slow-release behavior of slow-release fertilizer, but the heavy metal ions in the shell-Mg-P-metal were also slow released. The pot experiment results confirmed that the slow-release phosphorus fertilizers (shell-Mg-P and shell-Mg-P-metal) in the soil polluted in low concentration of heavy metals can reduce the amount of heavy metals in whole wheat seedlings and promote wheat seedling growth. However, the application of slow-release fertilizers increased the translocation efficiency (TFR to SL) of metal from root (R) to aboveground part (stem and leaves, SL), promoted the transportation of heavy metals from roots to the stems and leaves, and increased the safety risk of the wheat seedling edible. Therefore, besides the positive role of slow-release fertilizers in retaining heavy metals and reducing the amount of heavy metals in whole seedlings, the risk that it may aggravate the translocation of heavy metals to stems and leaves should be paid more attention, so as to ensure the safe and reliable application of slow-release fertilizers.

Response of rhizosphere microbial community of Chinese chives under different fertilization treatments.

Soil microorganisms play an irreplaceable role in agricultural production, however, an understanding of response of soil microorganisms to slow-release and common fertilizer applications is limited. In this study, different amounts of slow- release fertilizer were used to overwintering Chinese chives growing area in a plastic greenhouse to investigate the effects of on rhizosphere soil physicochemical properties and soil microbial communities (bacteria and fungi) of Chinese chives. The result displayed that application of slow-release fertilizer significantly improved soil nutrients, soil enzyme activity, and soil microbial community structure and diversity compared to conventional fertilizer application. Compared with T1 treatment, the content of total nitrogen (TN) and available phosphorus (AP), and the SU-E activity in the soil of T2 (NPK: 62.8 kg · 667 m-2) increased by 42.58%, 16.67%, and 9.70%, respectively, showing the best effects. In addition, soil bacterial diversity index and soil microbial community structure were improved as indicated by increased relative abundance of each species, such as Byssovorax, Sandaracinus, and Cellvibrio. Oppositely, the both soil fungal diversity and the number of species decreased after fertilizationthe relative abundance of Ascomycota increased in each fertilization treatment detected by ITS sequencing. Further, the relative abundance of pathogenic fungi such as Pezizomycetes, Cantharellales, and Pleosporales decreased in the T2 treatment. Principal Coordinates Analysis (PCoA) showed that both the amount of fertilizer applied and the type of fertilizer applied affected the soil microbial community structure. RDA evidenced that soil bacteria, Proteobacteria and Gemmatimonadetes, were closely correlated with soil AN, SOM, and AK. Acidobacteria were closely correlated with soil pH, TN, and AP. Ascomycota was closely correlated with soil pH and TN. In conclusion, the application of slow-release fertilizers and reduced fertilizer applicationcould improve soil physical and chemical properties as well as soil microbial community structure and diversity, contributing to sustainable soil development. The recommended fertilization rate for overwintering Chinese chives is NPK: 62.8 kg · 667 m-2.

Response of bacterial compositions to the use of slow-release fertilizers with long-acting agents and synergists

Slow-release fertilizer (SRF) is a new type of fertilizer, which is consistent with the physiological nutrient requirements of crops, but can also improve fertilizer utilization by reducing the total amount of fertilizers and the number of applications. However, its effects on soil fertility and bacteria in sugarcane fields are not clear. This study investigated the proper usage of SRF and the long-term application of SRF on soil fertility and health in sugarcane fields, seven fertilization treatments were set up as follows: SRF + 125 g/t long-acting agent (A), SRF +150 g/t long-acting agent (B), SRF + 235 g/t long-acting agent (C), SRF + 3 kg/t synergists (D), SRF + 8 kg/t synergists (E), SRF + 18 kg/t synergists (F) and traditional fertilization (CK). Traditional and Illumina HiSeq high-throughput sequencing technologies were used to compare and analyze soil enzyme activity, microbial biomass, and other biological traits and bacterial diversity. The results showed that sugarcane yields could be significantly increased by the application of SRFs. Meanwhile, soil fertility, which was represented by the content of total organic matter, nitrogen, phosphorus, and potassium, or the available nitrogen, phosphorus, and potassium, were all significantly improved or similar to those of CK. Moreover, the bioindicators of soil fertility, such as the activities of soil enzymes (β-Glucosidase, aminopeptidase, and phosphatase) and soil microbial biomass (carbon, nitrogen, and phosphorous), were also significantly increased or similar to those of CK in most of the SRFs treatments. In comparison with CK, soil microbial diversity, richness, and soil bacterial community structures were not significantly altered in sugarcane fields under different SRFs applications. In addition, although unclassified_f__Acetobacteraceae, Humibacter, and norank_f__Caulobacteraceae were the unique dominant bacterial genera in CK, some soil bacterial genera, such as unclassified__Subgroup_6, unclassified__Subgroup_2 and unclassified__IMCC26256 were also enriched as the special soil dominant bacterial genera in all or parts of the SRFs treatments. i.e., soil bacterial community structures also were not destroyed by SRFs application which compared to CK. In comparison to CK, cane yields increased significantly over three years, but soil fertility and health in sugarcane fields could also be improved or maintained by SRFs applications. All of the above results indicate that the traditional fertilization method for sugarcane production can be completely replaced by SRFs application. Furthermore, based on the cane yields and the prices of sugarcane and fertilizers in the local area, the treatment C can be concluded as the most cost-effective SRFs usage among the six SRFs treatments: A to F.

Fertilization methods affecting ‘Tahiti’ lime (Citrus latifolia) fruit yield and profitability

In Puerto Rico, the most commonly planted citrus crops are oranges, mandarins and limes. Farmers still have an interest in citrus production despite the detrimental effect of the Huanglongbing (HLB) disease on island orchards. Vector control and use of slow-release fertilizers (SRF) and soluble fertilizer (SF) applications to the soil are among the recommended management practices to increase citrus production. In 2009, the Department of Agriculture of Puerto Rico (DAPR) appointed the fruit tree specialist from the University of Puerto Rico and a DAPR staff member to evaluate the condition of citrus production in Puerto Rico. Based on that evaluation, DAPR developed an initiative to increase the number of marketable fruits of oranges, mandarins, and limes from trees between five and 12 years of age by promoting the use of SRF in combination with SF applications to the soil. An experiment was established during 2011 in a seven-year-old ‘Tahiti’ limeorchard in Ciales, Puerto Rico, to compare fertilization methods promoted by the DAPR with conventional methods, estimating the profitability of each method. The DAPR fertilizer recommendations were developed specifically for situations where HBL is present. In the orchards under study, HBL was not observed and therefore not tested. This does not mean that trees were not infected because symptoms may take months or years to become visible. The fertilization methods evaluated were: (1) granular fertilizers applied every four months (conventional fertilization), (2) manual application of SRF twice a year plus the application of SF to the soil with a backpack sprayer four times a year (SRF+SF/backpack), (3) manual application of SRF twice a year plus the application of SF to the soil with a motorized sprayer four times a year (SRF+SF/motorized), and (4) manual application of SRF twice a year. Total fruit number, total fruit weight, and average fruit weight were measured. Harvests were carried out monthly for 15 months. In the first seven harvests, the performance of trees submitted to the combination of SRF and SF was more efficient than was conventional fertilization or SRF alone, since the same production was maintained using a considerably lower amount of nutrients. At 14 months, the application twice a year of SRF alone almost doubled yield although the effect of this treatment was inconsistent during the year. We estimate that the combination of SRF and SF applications to the soil will result in the highest profitability with an income of $27 per tree per year and a profitability of $8.05 per dollar spent.

Effects of Mulching and Slow-release Fertilizer Application Reduction on Soil Microbial Community Structure in Rapeseed Field Under Two Different Rainfall Conditions

In order to investigate the effects of furrow and ridge rainwater harvesting, straw mulching, and reduced and slow-release fertilizer on soil microbial community structure of rapeseed, a two-year field study was conducted in rainy (2016-2017) and drought (2017-2018) seasons, which included three cultivation patterns:1 conventional flat planting, 2 straw mulching, and 3 ridge-furrow rainfall harvesting system and four fertilization patterns:1 conventional fertilization (100% of the amount), 2 reduced slow-release fertilizer Ⅰ (80% of the amount), 3 reduced slow-release fertilizer Ⅱ (60% of the amount), and 4 no fertilizer. The results indicated that it was rainy in 2016-2017, with seasonal drought during the nutritional growth stage in 2017-2018. The two technologies (straw mulching+80% slow-release fertilizer, J80 and ridge-furrow rainfall harvesting system+80% slow-release fertilizer, M80) were beneficial to boost the soil microbial activity. J80 and M80 increased the microbial biomass carbon by 9.94% and 10.32% and microbial biomass nitrogen by 2.38% and 1.19%, respectively, compared with that of the local cultivation pattern under two different climate conditions. The total amount of microbial phospholipid fatty acid (PLFA) decreased by 30.75% in the rainy year compared with that in the drought year, and mulching technology could effectively increase the total amount of soil PLFA. The PLFA contents of soil bacteria and fungi in the rainy year were 33.67% and 53.21%, respectively, lower than those in the drought year. However, the PLFA content of actinomycetes increased by 13.04%. Microbial communities were sensitive to abnormal precipitation. The bacteria/fungi ratio increased in rainy weather. The drought climate heighted the ratio of straight chain saturated fatty acid/straight chain monounsaturated fatty acid and straight chain monounsaturated fatty acid/cyclopropane acid. In conclusion, adopting the optimal cultivation technologies can stabilize the soil microenvironment under abnormal precipitation, relieve water and nutrient stress, and provide an effective means for rapeseed sustainable development.

Delaying application time of slow-release fertilizer increases soil rhizosphere nitrogen content, root activity, and grain yield of spring maize

Application of slow-release fertilizer (SF) is a nutrient-management measure aimed at improving maize nutrient use and yield and saving labor cost. One-time application of SF at sowing usually results in nutrient deficiency during the post-silking stage, owing to the long growth period of spring maize. This study was conducted to investigate the effects on spring maize of SF application stage (zero, three-, and six-leaf stages, designated as SF0, SF3, and SF6, respectively) on grain yield, total soil rhizosphere nitrogen (N) content, and root activity, in comparison with the conventional fertilization mode (CF, application of compound fertilizer at sowing time, and topdressing urea at six-leaf and tasseling stages) at the same fertilization level as the control. Compared with no fertilization (F0) and CF, SF increased grain number and weight. The maize cultivars Suyu 30 (SY30) and Jiangyu 877 (JY877) produced the highest grain yield and net return under SF6 treatment over the three years. SF6 increased enzymatic activities including oxidoreductase, hydrolase, transferase, and lyase in rhizosphere soil at silking (R1) and milking stages (R3). SF6 increased the total N contents of rhizosphere soil by 7.1% at R1 and 9.2% R3 stages compared with SF0. The activities of antioxidant enzymes in roots were increased under SF6 treatments at R1 and R3. The mean root activities of SF0, SF3, and SF6 increased by 7.1%, 12.8%, and 20.5% compared with CF at R1 and by 8.8%, 13.0%, and 23.5% at R3. Delaying the application time of SF could increase grain yield by increasing total N content of rhizosphere soil, delaying root senescence, and increasing root activity at the late reproductive stage. Applying SF at the six-leaf stage is recommended as an effective fertilization strategy for the sustainable production of spring maize in southern China.

Effects of Mechanized, Deep Application of Slow-Release Fertilizer on Yield and Nitrogen, Phosphorus, and Potassium Utilization of Direct-Seeded Rice

Effects of Mechanized, Deep Application of Slow-Release Fertilizer on Yield and Nitrogen, Phosphorus, and Potassium Utilization of Direct-Seeded Rice

Biostimulant in acclimatization of micropropagated banana (Musa spp.) seedlings

Microorganisms, such as growth-promoting bacteria, may favor the obtaining of better-quality banana (Musa spp.) seedlings. This study aimed to evaluate the effect of inoculation with growth-promoting bacteria Bacillus sp. on micropropagated seedlings of banana cv. ‘Prata Catarina’ in the acclimatization phase. The design was in randomized blocks, with 4 treatments (negative control: no inoculation and no fertilization; positive control: application of slow-release fertilizer; inoculation with Bacillus sp. strain 186; and inoculation with Bacillus sp. strain 109) and 4 replicates (14 experimental units), totaling 224 seedlings. The bacterial population in the rhizosphere was quantified and the growth of seedlings and contents of minerals were evaluated. Seedlings treated with slow-release fertilizer showed better performance for the number of leaves (6.14 ± 1.44), shoot (3.64 g ± 1.72) and root (4.76 g ± 3.23) fresh weight and root dry weight (0.72 g ± 0.43). Using strains alone did not promote the growth of seedlings, under the conditions of the present study. Nevertheless, the strains were efficient in increasing the nitrogen content in leaves (17.93 g kg-1 ± 0.73, strain 109) and potassium and magnesium contents in roots (6.96 g kg-1 ± 0.39 and 6.98 g kg-1 ± 0.40, strain 186).