Controlled-release Fertilizer Treatments Research Articles

Contribution of soil sustainable management to improve coffee nutrition and mitigate water scarcity

The soil can be managed to improve plant nutrition and resilience under water scarcity. The objective of this study was to evaluate the contribution of soil conditioners, controlled-release fertilizers, and water availability levels to mitigate water scarcity and improve the nutrition of coffee plants. The experiment was conducted in a greenhouse under a randomized block design with four replicates in a factorial scheme (2 irrigation levels × 2 fertilizer types × 5 soil conditioners) of analysis of variance. The factors under study were two irrigation levels (low—40% of water holding capacity, and high—80% of water holding capacity), fertilizer type (conventional and controlled-release), and soil conditioners (coffee husk, gypsum, water-retaining polymer, organic compost, and control without soil conditioner), The characteristics assessed were soil fertility, soil moisture, and nutrient foliar contents. Multivariate analytical methods were used to interpret the results. Soil moisture, chemical attributes, and leaf nutrient contents were analyzed. There was a similarity in the clusters formed by the controlled-release fertilizer treatments, which contribute to plant nutrition. Even under water restriction, the treatments with coffee husk and organic compost were clustered along with soil moisture, favoring the absorption of nutrients. Soil cover with organic compounds improved soil moisture, even under low water availability, which favored plant fertility and nutrition.

Eco-friendly cellulose hydrogels as controlled release fertilizer for enhanced growth and yield of upland rice

The effect of urea-loaded cellulose hydrogel, a controlled-release fertilizer (CRF) on growth and yield of upland rice were investigated in upland rice. As with the initial research, nitrogen (N) treatments were applied as CRF treatments; T2H (30 kg N ha−1), T3H (60 kg N ha−1), T4H (90 kg N ha−1), T5H (120 kg N ha−1) and recommended dose of fertilizer (RDF) at 120 kg N ha−1 RDF (T6U) in split application and T1 (0 N) as control. Results from this study indicated that applying CRF at the optimum N rate, T4H resulted in maximum grain yield, increasing by 71%. The analysis of yield components revealed that higher grain yield in T4H CRF was associated with an increase in panicle number and number of grains per panicle. Maximum grain N uptake of 0.25 g kg−1 was also observed in T4H CRF. In addition, T4H CRF recorded the highest harvest index (HI) and N harvest index (NHI) of 45.5% and 67.9%, respectively. Application of T4H CRF also recorded the highest N use efficiency (NUE) and N agronomic efficiency (NAE), 52.6% and 12.8 kg kg−1, respectively. Observations show that CRF with only 75% N applied (T4H) in soil improved grain yield when compared to CRF with 100% N and 100% RDF in farmers’ conventional split application. This suggested that CRF with a moderate N application might produce the highest potential yield and improved N efficiencies while enhancing crop production and further increase in N supply did not increase yield and N efficiencies. The results suggest that the application of T4H CRF for upland rice would enhance HI, N efficiencies and improve the yield of upland rice. Also, all growth parameters and yield were positively influenced by the application of CRF as a basal dose compared to split application of conventional urea fertilizers.

Evaluation of Controlled Release Fertilizer on Bulb Yield, Nutrient Content, and Storage Quality of Overwintering Intermediate-Day Onions

Controlled release fertilizer (CRF) can delay its availability for plant uptake and increase fertilizer use efficiency, which might be useful for overwintering onion (Allium cepa L.) which has a growing season of 7 to 8 months. The study was performed to evaluate the effect of CRF on bulb yield, nutrient content, and storage quality of intermediate-day onions in onion growers’ fields during the 2013/2014 and 2014/2015 growing seasons. The formulation of CRF used was 18N-3.1P-7.5K, and as an N source, 50% polymer-coated urea-N and 50% urea-N plus diammonium phosphate-N were blended. Treatments included CRF 25%, CRF 50%, CRF 100%, or CRF 150% based on the soil test recommended N rate. Separated NPK fertilizers of single application (NPK once), three-split application (NPK 3-split) and non-fertilized plot were checks. Soil NO3-N content in all CRF treatments and NPK once peaked at 133 days after transplanting. Marketable bulb yields for NPK once and CRF 150% was 66.12 Mg ha-1 and 65.67 Mg ha-1, respectively, on a 2-year average, which were not significantly greater than CRF 50%, CRF 100%, and NPK 3-split. Most nutrient uptakes in the bulb were not different among all treatments except for no fertilization. Apparent nutrient recovery of CRF 25% was 32.5% in N, 20.9% in P, and 76.1% in K on a 2-year average, approximately twice that of CRF 100%. Total flavonoids content was higher in CRF 25% than in other treatments. The 50% reduced CRF rate based on the soil test recommended N rate should satisfy crop demand of available nutrients when electric conductivity was more than 1.5 dS m-1 and organic matter was 35 g kg-1 in preplant soil.Comparison of bulb yield characteristics of onion as affected by application rates of controlled release fertilizer (CRF) and application methods of NPK fertilizer. Treatments Marketable yield (Mg ha-1) Unmarketable yield (Mg ha-1) Stand reduction (%) Large† Medium Small Total 2013/2014 CRF 25%‡ 52.98 ns§ 27.48 ns 1.26 ns 81.73 ns 1.29 ns 2.8 ns CRF 50% 62.67 22.44 0.67 85.79 0.69 2.3 CRF 100% 67.81 19.62 0.45 87.87 0.94 4.6 CRF 150% 68.31 22.00 0.58 90.89 0.55 1.9 NPK once 69.16 18.81 1.49 89.47 1.21 2.8 NPK 3-split 68.08 19.13 0.50 87.71 0.80 5.1 No fertilization 60.71 22.08 1.49 84.29 0.56 5.6 2014/2015 CRF 25% 3.28 ns 24.41 ns 10.37 b 38.07 ns 0.80 ns 7.90 ab CRF 50% 2.87 29.07 8.96 b 40.89 0.48 8.94 a CRF 100% 2.10 22.69 10.28 b 35.07 0.97 8.31 a CRF 150% 3.16 27.14 10.14 b 40.44 0.72 6.30 ab NPK once 4.43 28.24 10.10 b 42.77 1.02 6.83 ab NPK 3-split 2.33 28.68 10.88 b 41.88 0.68 4.88 b No fertilization 0.67 14.92 17.18 a 32.78 0.33 7.17 ab F-test Year (Y) ** ns ** ** ns ns Fertilizer (F) ns ns ** ns ns ** Y × F ns ns ** ns ns ns †Size categories in bulb diameter: large (≥8.0 cm), medium (≥6.0 and <8.0 cm), small (≥4.0 and <6.0 cm), and cull (<4.0 cm).‡CRF 25%, 50%, 100% and 150% rates based on soil test recommended N rate; NPK once = single application of N, P and K with 100% rate based on soil test recommended N, P and K rate; NPK 3-split = basal and 2-split applications of N, P and K.§Fisher’s protected least significant difference (p ≤ 0.05). ns, *, **: not significant or significant at p ≤ 0.05, p ≤ 0.01.

Fertilizantes de liberação controlada, orgânico ou organomineral para produção de palmeira areca

Abstract The areca palm is an ornamental plant widely used in Brazil for decoration and landscaping. The proper use of fertilizers and balanced fertilization are among the main factors that promote the rapid development of these plants and affect their technical and economic aspects. Because of the need to elucidate areca palm nutrition, this study aimed to evaluate the use of mineral (conventional or controlled release), organic, or organomineral fertilizers in the production of areca palm in pots. The experiment was conducted for a year under a 70% shading screen using a completely randomized design, with seven treatments and six replications. The treatments consisted of different fertilizers: control: no fertilizer; mineral: 10-10-10; controlled release mineral: 14-14-14, mineral with 50% N and K release controls: 16-06-18, mineral: 13-05-13, organomineral: 16-06-09, and organic. The experiment consisted of measuring the vertical height of the plant and determining the Falker Chlorophyll Index (FCI) a and b. All fertilizers used in the experiment provided gains in growth and green color (Chlorophyll Index) in the areca palm grown in pots relative to the absence of fertilization. The three-month controlled-release fertilizer treatment produced the best results, positively impacting the areca palm production, both in terms of plant height and color, which are attributes that increase the product’s commercial value.

Comparative Approach on the Effects of Soil Amendments and Controlled-Release Fertilizer Application on the Growth, Nutrient Uptake, Physiological Performance and Fruit Quality of Pepper (Capsicum annuum L.) Plants

Under the economic pressure from the increase of fertilizers’ prices due to the recent energy crisis, more efforts are needed to search for alternative and cheaper sources of nutrients for crops. The purpose of our study was to compare the effects of manure and inorganic amendments’ application to those derived from the application of a controlled-release fertilizer (CRF) on the growth, nutrition, physiology and fruit quality of pepper plants. For that reason, zeolite (ZEO) and vermiculite (VER) were applied either independently, or in combination between them, or with manure (MAN), in a pot experiment. Insignificant differences for plant growth among the treatments were recorded, while higher foliar N, Mg and Mn concentrations were determined in CRF. In contrast, a significantly higher K uptake was recorded in the ZEO and VER + ZEO treatments; the highest leaf P levels (0.47 and 0.44% D.W.) were recorded in the MAN + VER and ZEO treatments, respectively. The optimum photosynthetic II (PSII) performance was observed in the VER and in the MAN + ZEO (based on the performance index—PI) treatments. The highest stomata opening was found in the CRF treatment, while the photosynthetic rate of pepper plants showed its maximum values both in the CRF and VER treatments. Finally, fruit quality (as indicated by total soluble solids, total phenols and antioxidant activity—FRAP) was significantly influenced by treatment. In conclusion, significant differences in the growth, nutrition and physiological performance of pepper plants between soil amendments’ application (inorganic, such as zeolite and vermiculite, and organic, such as manures) and CRF application were recorded; thus, these amendments should be more thoroughly studied in future projects to investigate if they could partially decrease high inorganic fertilization rates in Capsicum annuum L.

An Integrated Nitrogen Management Strategy Promotes Open-Field Pepper Yield, Crop Nitrogen Uptake, and Nitrogen Use Efficiency in Southwest China

Excessive nitrogen (N) fertilizer application is a serious issue in intensive vegetable production and can negatively affect vegetable productivity and N use efficiency (NUE). The optimization of the N fertilizer rate and application of enhanced efficiency N fertilizers (EENFs), including nitrification inhibitors (Nis) and controlled-release fertilizer (CRF), are widely recognized as feasible N management strategies to resolve the problem of unreasonable N fertilizer input. Therefore, we conducted a 2-year field experiment (2019–2020) in an open-field vegetable system (pepper, Capsicum annuum L.) in southwest China to investigate the effects of an optimized N application rate and EENFs on vegetable yield, NUE, and crop N uptake. The following N management treatments were established: control without N fertilizer input (CK); optimized N fertilizer rate as urea (OPT); farmers’ fertilizer practice (FP); application of a nitrification inhibitor (NI) within the optimized N fertilizer rate; and application of controlled-release fertilizer (CRF) within the optimized N fertilizer rate. The results showed that the OPT treatment based on root zone N management achieved a 37.5% reduction in the N application rate without compromising vegetable yield and increased the recovery efficiency of N (REN) by 31.5% compared to the FP treatment. Furthermore, the combined application of the NI or CRF treatments with the OPT treatment resulted in greater vegetable yields, fruit N uptake, and REN (9.54%, 26.8%, and 27.6%, respectively, for NI; 10.5%, 28.7%, and 28.8%, respectively, for CRF) than the OPT treatment alone. The absorption ratio of fruit N uptake to total crop N uptake was also increased. Our results clearly showed that the combined application of EENFs with the OPT treatment could achieve the win–win benefits of a yield increase and improved REN in Chinese vegetable production.

Comparison of two controlled-release fertilizer formulations for cut-and-come-again harvest yield and mineral content of Lactuca sativa L. cv. Outredgeous grown under International Space Station environmental conditions

Red Romaine leaf lettuce (Lactuca sativa L. cv. Outredgeous) was grown in ground-based analogues of the Veggie plant-growth units used to grow salad vegetables for astronauts on the International Space Station (ISS). Plants were grown for 56 days with three “cut-and-come again” leaf harvests from the same plants. Six Biomass-Production-Systems-for-Education (BPSe) units were used to grow ‘Outredgeous’ (‘OR’) lettuce in a walk-in growth chamber under temperature, humidity, and LED-lighting conditions similar to those occurring in Veggie on ISS. Because of the ISS micro-gravity environment, both Veggie and ground-based BPSe units utilize one-way capillary wicking of water into an arcillite clay root substrate. In the present study, two different controlled-release fertilizer (CRF) formulations incorporated into the arcillite were compared for effects on ‘OR’ growth rate, overall yield, and mineral content of leaves harvested from the same plants 28, 48, and 56 days after planting. Both CRF treatments had a rapid-releasing T70 component that kept growth rate equivalent over the first two harvests. Growth rate for both CRF treatments increased from the first to the second harvest, but then declined from the second to the third harvest, more so for the slower-releasing T180 CRF than for the moderately-releasing T100 CRF. Tissue content of the macro-nutrients N, P, and K declined at each harvest for both CRFs, while content of the micro-nutrients B, Zn, and Mn increased. Although pH did not go out of the nominal range for availability of mineral nutrients to roots over the cropping cycle, and electrical-conductivity of rootzone salts was neither excessive nor depleted, tissue macronutrient depletion and micro-nutrient accumulation may have contributed to yield declines. Although either CRF formulation can support adequate yield of ‘OR’ lettuce over a 56-day period, the moderately-releasing T100 formulation tends to give slightly higher yield, especially during the last growth increment, and with non-deficient mineral content.

Combined Fertilization Could Increase Crop Productivity and Reduce Greenhouse Gas Intensity through Carbon Sequestration under Rice-Wheat Rotation

Quantifying greenhouse gas intensity (GHGI) and soil carbon sequestration is a method to assess the mitigation potential of agricultural activities. However, the effects of different fertilizer amendments on soil carbon sequestration and net GHGI in a rice-wheat cropping system are poorly understood. Here, fertilizer treatments including PK (P and K fertilizers); NPK (N, P and K fertilizers), NPK + OM (NPK plus manure), NPK + SR (NPK plus straw returning), and NPK + CR (NPK plus controlled-release fertilizer) with equal N input were conducted to gain insight into the change of soil organic carbon (SOC) derived from the net ecosystem carbon budget (NECB), net global warming potential (GWP), and GHGI under rice-wheat rotation. Results showed that compared with NPK treatment, NPK + OM significantly increased wheat yield and NPK + SR caused significant increase in rice yield. Meanwhile, NPK + SR and NPK + CR treatments reduced net GWP by 30.80% and 21.83%, GHGI by 36.84% and 28.07%, respectively, which suggested that improved grain production could be achieved without sacrificing the environment. With the greatest C sequestration, lowest GHGI, the NPK plus straw returning practices (NPK + SR) might be the best strategy to mitigate net GWP and improve grain yield and NUE in the current rice-wheat rotation system.

Effects of controlled release fertilizer ratio on yield formation and nitrogen absorption and utilization of late-maturing medium &amp;lt;italic&amp;gt;japonica&amp;lt;/italic&amp;gt; rice under different mechanized cultivation methods

<p id="C3">Rice cultivars of Nanjing 9108 with good taste quality was adopted as material under the pure nitrogen condition of 270 kg hm^-2in this study. Rice was cultivated with two methods including mechanical transplanting with pothole seedlings (MT) and mechanical transplanting with carpet seedlings (MC). Controlled-release fertilizer and quick-acting nitrogen fertilizer were mixed at a ratio of 5:5. Controlled-release fertilizer was mixed from four different release periods (40, 80, 100, and 120 days) at a ratio of 1:4 to form three mixing modes (40+80, 40+100, and 40+120). Conventional urea split fertilization (CK) was used as a control, and the effects of different controlled-release fertilizer ratios on yield formation and nitrogen accumulation of high-quality <italic>japonica</italic> rice were studied. Under the same fertilizer treatment, compared with mechanical transplanting with carpet seedlings (MC), the two-year yield of mechanical transplanting with pothole seedlings (MT) was significantly increased by 3.9% and 4.9%, respectively. The reason was that the transplanting of pothole seedling machine could improve the accumulation of photosynthetic substances in the middle and late stages and obtain larger panicle type with higher grain number per panicle, seed setting rate, and 1000-grain weight. Under the cultivation mode of pothole seedling transplanting and carpet seedling transplanting, compared with CK, the two-year yield of 40+80 and 40+100 controlled-release fertilizer treatments were higher than CK, and the two-year yield of 40+100 controlled-release fertilizer treatments was the highest, which was significantly increased by 7.3% and 9.2%, respectively. The reason was that 40+100 controlled-release fertilizer treatment had higher effective panicle number and population glume amount. Compared with 40+80 and 40+120 controlled-release fertilizer treatments, the nutrient absorption law of 40+100 controlled-release fertilizer treatment was more consistent with Nanjing 9108, which not only ensured the occurrence of early tillering, but also ensured the stable production of photosynthetic substances at later stage, thus obtaining stable panicle number, grains per panicle, and 1000-grain weight. Compared with CK, the nitrogen recovery efficiency, nitrogen agronomic efficiency, nitrogen physiological efficiency, and nitrogen partial productivity of 40+100 controlled-release fertilizer treatments were significantly increased by 10.0%-12.5%, 24.6%-30.5%, 11.4%-18.6%, and 7.3%-9.1%, respectively. In conclusion, the mechanical transplanting with pothole seedlings (MT) had obvious advantages over mechanical transplanting with carpet seedlings (MC), which was a cultivation method that was conducive to high-quality <italic>japonica</italic> rice. At the same time, the 40+100 controlled-release fertilizer ratio could better meet the nutrient requirements of good-quality <italic>japonica</italic> rice at various stages, and could obtain high yield, which could be used as a simplified fertilization scheme for high-quality <italic>japonica</italic> rice.

Estimation of Greenhouse Gas Emission in Rice Paddy Soil Under Slow Released N Fertilizer Application: Annual Investigation

Intermittent drainage can reduce methane (CH4) emission from rice paddy soils, but nitrous oxide (N2O) emission can increase. We believe that the slow released N fertilizer can mitigate N2O emissions by reducing N lost to the environment. In this study, we tried to assess the influence of slow N fertilizer on effective greenhouse gas (GHG) reduction. We installed three different treatments, urea (U) treatment, controlled release fertilizer (CRF) treatment, and hairy vetch with urea (HV) treatment. The emission rates of CH4 and N2O were monitored using the closed chamber method during cropping and fallow season. The grain yield was investigated to calculate yield scaled greenhouse gas intensity (GHGI). Compared with U treatment, CH4 emission was reduced in CRF but increased in HV treatment. In contrast, N2O emission was increased in CRF but reduced in HV treatment. Grain yield was increased in CRF and HV treatment than U treatment. The GHGI was the lowest in CRF treatment by high grain yield and low GHG emission. In contrast, GHGI was the highest in HV treatment due to increased CH4 emission. In conclusion, controlled release fertilizer can effectively reduce GHG emission. However, CRF application increased N2O emissions during the fallow season, and further investigation is needed to determine whether this is due to the effect of fertilizer residues. In addition, due to field experiments that are easy to influenced by the environmental condition, it seems necessary to verify the research results through additional investigations over many years. Grain yield, total GWP and GHGI during annual season in rice paddy under difference type of nitrogen fertilizer application.

Inorganic and Organic Amendments Affect Soil Fertility, Nutrition, Photosystem II Activity, and Fruit Weight and May Enhance the Sustainability of Solanum lycopersicon L. (cv. ‘Mountain Fresh’) Crop

One of the most important issues for modern agriculture is how to decrease fertilization rates and enhance the sustainability of crops, without decreasing yields. Two inorganic (zeolite—zeo; vermiculite—ver) amendments and their mixtures with an organic soil amendment (goat manure) (i.e., zeo + ver, manure + ver, manure + zeo) were tested, and compared to the application of a controlled release fertilizer (CRF), in order to investigate if they were able to satisfy the nutritional needs of Solanum lycopersicon L. plants. For this purpose, a 112-day pot experiment was performed. After zeo and manure application, exchangeable K was increased from 16.5 times to 37.5 times. At the end of the experiment, total plant biomass was significantly higher in the CRF treatment, compared to the ver treatments (ver, ver + manure). Leaf K concentration was significantly higher in the zeo treatment (5.93% dw), compared to those determined in the CRF, ver, and ver + manure. In contrast, significantly higher foliar N was found in the CRF (4.83% dw) and zeo + ver (4.24% dw) treatments, compared to manure + ver. Finally, photosystem II (PSII) activity was significantly higher in ver, and this was ascribed to the optimum foliar Mn found in this treatment (138 mg kg−1 dw). It is expected that these data will provide a thorough insight towards decreasing chemical fertilization inputs and enhancing the sustainability of Solanum lycopersicon L. crop.

Hydroponic Fertilizer Supply for Basil Using Controlled-release Fertilizer

Small-scale hydroponics is a growing urban horticulture trend, but nutrient solution management remains a challenge for small growers. The objective was to investigate the potential to use controlled-release fertilizer (CRF) to simplify nutrient management in small-scale hydroponic systems. Three experiments were conducted with the goal of a single fertilizer application during the crop cycle of basil (Ocimum basilicum). Nutrient release curves were quantified by adding prills to water and measuring nutrient content weekly in the solution for CRF products without plants. In all seven products tested (Osmocote Bloom 2–3M, Osmocote Plus 3–4M, E-Max Calcium Nitrate 2–3M, Agrocote MAP 3–4M, E-Max Keiserite 3–4M, E-Max K-Mag 2–3M, and Agrocote SOP 3–4M) an initial rapid release was followed by a plateau, but release rates differed between products varying from 100% (MgSO4) to 60% release [(NH4).(H2PO4)] over an 11-week evaluation period. Total nutrient content in two commercial N–P–K CRF products (3–4 months 15N–3P–10K and 2–3 months 12N–3.1P–14.9K) provided lower Ca and Mg compared with a typical hydroponic solution based on water-soluble fertilizer (WSF). A subsequent experiment evaluated plant growth response using the same two commercial CRF products (single application) or a WSF (replaced weekly) in growth chamber environment. Plants grown for 4 weeks under CRF treatments yielded less than half the shoot fresh weight of plants grown with WSF and exhibited symptoms of Ca deficiency and micronutrient toxicity (confirmed with tissue analysis). Electrical conductivity (EC) of CRF solutions increased over time indicating excess dose compared with plant uptake, reaching a maximum of 5.4 dS·m−1. Nutrient release curves from the first experiment were then used to estimate product release and create a single-application nutritional program based on a customized “Blend” developed from CRF macronutrients plus WSF micronutrients. Plants were grown hydroponically with two dosages of Blend (1X and 2X) and compared with a commercial WSF with weekly replacement of solution. Blend 2X and WSF treatments had similar shoot fresh weight (241 and 244 g/four plants, respectively) with healthy plant appearance and tissue nutrient levels generally within published survey ranges for basil. Commercial CRF products designed for soil or container production were unsuitable for hydroponics, but acceptable plant performance with the customized CRF Blend demonstrated proof-of-concept for a single CRF application.

Comparative study effects between manure application and a controlled-release fertilizer on the growth, nutrient uptake, photosystem II activity and photosynthetic rate of Olea europaea L. (cv. ‘Koroneiki’)

Organic fertilization has been proposed as an alternative method, in the frame of sustainable agriculture, to enhance soil fertility and satisfy the nutritional needs of crops, without the input of chemical fertilizers. A six-month pot experiment, with 3 soil amendments, used as organic fertilizers (cow manure-CM, goat manure-GM, and their mixture, i.e. CM + GM) and a controlled release fertilizer (CRF) was conducted, in order to investigate if the growth, nutrient uptake, photosystem II (PSII) activity, photosynthetic rate and total sugars of Olea europaea L. (cv. ‘Koroneiki’) plants were influenced by the kind of fertilization. The highest plant biomass, macronutrient content and PSII activity were found in the CRF treatment. In contrast, significantly lower photosynthetic and transpiration rates were recorded in the CRF due to the lower stomatal conductance. Translocated sugars were higher in the CM + GM treatment, while total sugar concentration did not significantly differ among the treatments. Despite the highest content of all macronutrients, Fe and Mn recorded in the CRF, the lowest foliar P, K, Mg, Zn and Cu concentrations revealed that the higher nutrient accumulation, compared to the organic treatments, should be ascribed to the higher plant biomass, rather than to higher nutrient uptake. From the above data, it is clear that the kind of organic/inorganic fertilization significantly influenced soil organic C content, fertility, growth, nutrient uptake and the physiology of olive plants. Thus, the kind of manure(s) used to enhance soil fertility and support crop production should be seriously taken into consideration by the olive growers before its/their use.

Fertilizer Source and Irrigation Depth Affect Nutrient Leaching During Coleus Container Production

Abstract Nutrient leaching during nursery container production can have negative effects on plant growth and the environment. The objective of this study was to evaluate effects of fertilizer source at two irrigation depths on nutrient leaching during coleus [Plectranthus scutellarioides (L.) Codd] ‘Solar Sunrise' container production to develop best management practices. Coleus received no fertilizer, a controlled-release fertilizer (CRF), or a water-soluble fertilizer (WSF) applied at 0.30 kg N and P per m3 (0.02 lb per ft3) and were irrigated at 1.9 or 3.8 cm.day−1 (0.7 or 1.5 in.day−1) for 56 days after planting (DAP). Leachate was analyzed every 7 DAP for inorganic N and dissolved total P (DTP). At 56 DAP, root biomass, leaf quality, and plant growth index were similar between CRF and WSF treatments at both irrigation depths. Highest inorganic N and DTP losses occurred within 21 DAP. Application of WSF resulted in higher cumulative N and DTP losses compared to CRF applications. Coleus irrigated at 3.8 cm.day−1 and fertilized with WSF resulted in higher DTP losses compared to CRF applications regardless of irrigation depth. Reducing irrigation reduced inorganic N leaching for each fertilizer source. Application of CRF provided consistent growth while curbing nutrient losses across both irrigation depths compared to WSF. Index words: controlled-release fertilizer, water-soluble fertilizer, nursery producers, best management practices. Chemicals used in this study: Micronutrients mix (Micromax®); controlled-release fertilizer (Osmocote® Classic); water-soluble fertilizer (Grower's Special). Species used in this study: Coleus [Plectranthus scutellarioides (L.) Codd] ‘Solar Sunrise'.

Assessment of Pruning and Controlled-release Fertilizer to Rejuvenate Huanglongbing-affected Sweet Orange

Previous research has shown that Huanglongbing {HLB [causal agent Candidatus Liberibacter asiaticus (CLas)]}-affected sweet orange (Citrus sinensis) trees have a reduced root-to-shoot ratio, potentially due to the high rate of root death. The diminished root system cannot support the existing aboveground canopy and a cycle of imbalance begins. As a result, the tree enters into a continuous carbohydrate stress cycle and, eventually, the tree declines. Therefore, the goal of this study was to evaluate pruning as a strategy to adjust the root-to-shoot ratio to improve growth and productivity of HLB-affected trees. In Jan. 2015, a 3-year trial was initiated on a 14-year-old grove of ‘Hamlin’ sweet orange on Swingle citrumelo (Citrus paradisi × Poncirus trifoliate) rootstock that was symptomatic of HLB and produced less than 180 lb of fruit per tree. The four pruning treatments were as follows: 1) 0% pruning (no canopy removal), 2) 25% pruning (canopy removed), 3) 50% pruning (canopy removed), and 4) 80% pruning (canopy removed). In a split-plot design, two sources of fertilizer were evaluated in combination with the pruning: 1) conventional fertilizer [CNV (dry granular)] applied at 200 lb/acre nitrogen (N) in five split applications per year, and 2) controlled-release fertilizer (CRF) applied at 150 lb/acre N, split in three applications per year. Within each pruning treatment, half of the trees received CNV and the other half received CRF. The fertilizer treatments were applied in each of the 3 years; however, pruning was performed only once in the beginning of the experiment. The trees that were pruned produced new vegetative growth that looked healthy with no visual HLB symptoms (initially); however, the trees remained positive for CLas throughout the study as determined by quantitative real-time polymerase chain reaction. The 80% pruned trees grew vigorously over the course of 3 years but remained significantly smaller in canopy than control trees (0% pruning) for both CRF and CNV treatments. The 25% and 50% pruned tree canopies grew back and were similar in canopy size as 0% pruning (control) treatment by the end of year 2. At the end of the study, the use of CRF on 25% pruned trees resulted in a significantly higher leaf area index as compared with trees receiving CNV. A significant positive linear correlation was observed between canopy volume and root density; the root density decreased with intensive pruning. A significant positive correlation was also observed between canopy volume and yield, and a negative correlation between canopy volume and fruit drop. There were no significant increases in yield resulting from any pruning or fertilization treatments compared with controls (0% pruning). However, with the use of CRF, the amount of N and frequency of application were reduced. Overall, our results indicate that pruning did not improve the productivity of HLB-affected trees over the course of 3 years. Therefore, severe pruning is not a viable option to rejuvenate the HLB-affected trees.

Interaction of soil boron application with leaf B concentration, root length density, and canopy size of citrus affected by Huanglongbing

Good and balanced citrus nutrition is important for high fruit yields and improved tree performance. A study was conducted for 2 years to investigate the effect of soil application of boron (B) on leaf nutrient content, canopy size, and root length density (RLD). The study was conducted on 10-year-old Candidatus Liberibacter asiaticus (CLas)-infected Vernia sweet orange on Rough Lemon rootstock in a commercial grove east of St. Cloud, FL planted at 375 trees ha−1 on a traditional soluble dry nutrition and spray programs. Treatments were supplied with various ground-applied controlled-release fertilizer treatments containing B. Boron was applied at 0×, 2×, and 4× current University of Florida recommendation where 1× = 1.12 kg ha−1. Data collected included leaf B nutrient content, soil B concentration, trunk diameters, canopy volumes, soil electrical conductivity, and soil pH. The 0×, 2×, and 4× application rates corresponded with leaf nutrient contents ranging from 56 mg kg−1 and 88 mg kg−1 in March 2017, 162 mg kg−1 and 288 mg kg−1 in September 2017, and 122 mg kg−1 and 320 mg kg−1 in May 2018. Temporary, RLD decreased with time from March to September 2017 by 13, 30, and 37% at the 0, 2.24, and 4.48 kg B ha−1 and increased by 309, 258, and 306% at the 0, 2.24, and 4.48 kg B ha−1, respectively, from September 2017 to May 2018. No consistent pattern was established between soil B application with canopy size.

Effect of reducing N and regulated fertilization on N loss from wheat-maize rotation system of farmland in Chao soil region of North China Plain

The application of large amounts of nitrogen (N) fertilizer can result in soil N accumulation and consequently N loss. To address these problems in a wheat-maize rotation area of the North China Plain, a two-year field experiment (2016-2017) was conducted to examine the effects of three different N fertilizer strategies on crop yield, N uptake, N loss and soil inorganic N content. The treatments were: controlled-release fertilizer, microbial fertilizer, nitrification inhibitor and farmer's practice (control). The results showed that the wheat yield from the microbial fertilizer treatment in 2016 was significantly lower than that from the controlled-release fertilizer treatment and the nitrification inhibitor treatment, but was not significantly different from conventional farmer fertilization. The N uptake of wheat and annual crops in the microbial fertilizer treatment was significantly reduced. There was no significant difference in crop yield and N uptake among the treatments in 2017. Soil fertility of the tillage layer was maintained or improved in all three treatments compared with the control, and the contents of alkali-hydrolyzed nitrogen, available potassium and organic matter increased with the increase of plant growth period in the microbial fertilizer treatment. Microbial fertilizer and nitrification inhibitor reduced the inorganic N content in the 40-100 cm soil profile, while controlled-release fertilizer increased the inorganic N content in the 0-40 cm soil layer. N loss through ammonia volatilization was higher than that through leaching, which was greater than the loss through N2O emission. Runoff loss was negligible. Among the treatments, N loss in farmer's practice treatment was the highest. Microbial fertilizer significantly reduced N loss through ammonia volatilization, but the loss through leaching was larger. In conclusion, with reduced N application compared with the farmer's practice, controlled release fertilizer and nitrification inhibitor could maintain crop yield and N uptake, and microbial fertilizer could ensure crop yield and N uptake for a longer plant growth period. The results suggested that inorganic N content in the 40-100 cm soil layer could be reduced in the soil by adding microbial fertilizer and nitrification inhibitors, and the amount of inorganic N was not reduced significantly by application of controlled release fertilizer. Several N reduction measures could reduce N loss. The microbial fertilizer treatment needed to be modified to reduce N leaching.

Effects of controlled-release fertilizer on nitrous oxide and nitric oxide emissions during wheat-growing season: field and pot experiments

Outdoor pot and field experiments were conducted to study the effect of controlled-release fertilizer (CRF) on nitrous oxide (N2O) and nitric oxide (NO) emissions and wheat yields during the 2011–2013. Three treatments, namely conventional N fertilizer (CF; urea and compound fertilizer, 300 kg N ha−1), CRF (210 kg N ha−1, which is 70% of the N applied in the CF treatment), and check (CK, 0 N), were applied in three replicates. The soil temperature, soil moisture, N uptake by wheat, wheat yield, and variations in NO3–N, NH4–N, N2O, and NO emissions were measured. Results showed that the average total N2O and NO emissions in the CRF treatment in the pot and field experiments decreased by 26.5 and 19.4%, respectively. The average N2O and NO emission factors decreased by 32.1 and 24.8%, respectively, compared with the CF treatment. However, the CRF wheat yields were insignificantly lower than those from the CF treatment. Results indicated that CRF could improve the efficiency of fertilizer N use, reduce labor cost, and increase economic benefit without sacrificing the yield.

Effects of controlled release blend bulk urea on soil nitrogen and soil enzyme activity in wheat and rice fields

A field experiment was conducted to investigate the effect of controlled-release fertilizer (CRF) combined with urea (UR) on the soil fertility and environment in wheat-rice rotation system. Changes in four forms of nitrogen (total nitrogen, ammonium nitrogen, nitrate nitrogen, and microbial biomass nitrogen) and in activities of three soil enzymes participating in nitrogen transformation (urease, protease, and nitrate reductase) were measured in seven fertilization treatments (no fertilization, routine fertilization, 10%CRF+90%UR, 20%CRF+80%UR, 40%CRF+60%UR, 80%CRF+20%UR, and 100%CRF). The results showed that soil total nitrogen was stable in the whole growth period of wheat and rice. There was no significant difference among the treatments of over 20% CRF in soil total nitrogen content of wheat and rice. The soil inorganic nitrogen content was increased dramatically in treatments of 40% or above CRF during the mid-late growing stages of wheat and rice. With the advance of the growth period, conventional fertilization significantly decreased soil microbial biomass nitrogen, but the treatments of 40% and above CRF increased the soil microbial biomass nitrogen significantly. The soil enzyme activities were increased with over 40% of CRF in the mid-late growing stage of wheat and rice. By increasing the CRF ratio, the soil protease activity and nitrate reductase activity were improved gradually, and peaked in 100% CRF. The treatments of above 20% CRF could decrease the urease activity in tillering stage of rice and delay the peak of ammonium nitrogen, which would benefit nitrogen loss reduction. The treatments of 40% and above CRF were beneficial to improving soil nitrogen supply and enhancing soil urease and protease activities, which could promote the effectiveness of nitrogen during the later growth stages of wheat and rice. The 100% CRF treatment improved the nitrate reductase activity significantly during the later stage of wheat and rice. Compared with the treatments of 40%-80% CRF, 100% CRF reduced the soil nitrate content of 20-40 cm soil layer in wheat significantly suggesting it could reduce the loss of nitrogen.

Effects of Controlled-Release Fertilizer Placement on Nutrient Leaching and Growth of Bedding Impatiens

Bedding impatiens plants were grown with a 16N-3.9P-10K controlled-release-fertilizer (CRF) of 5–6 or 8–9 month longevities placed at four positions in the container: top-dressed, incorporated, top-one-third, and bottom. These were compared to plants grown with a 20N-4.4P-16.6 water-soluble fertilizer (WSF) at a rate of 150 mg·L−1 nitrogen (N) (150 ppm N). All treatments received the same volume of tap water (CRF treatments) or fertilizer solution (WSF treatment), which was enough to achieve a 20 to 30% leaching fraction. Leachates were collected and measured at each irrigation and the concentrations of N, phosphorous (P), and potassium (K) were measured. Shoot dry weight (SDW) and canopy cover (CC) were also determined. Fertilizing with WSF produced plants of similar size as CRF treatments. CRF applied at the bottom of the substrate leached the highest amount of N among all treatments. Higher concentrations for most nutrients were measured in the leachates from containers treated with 5–6 month CRF during the first 20 d after planting than the next 23 to 34 days. The higher levels of nutrients in the leachates observed within two weeks after planting does not support the use of 5–6 month CRF at the application rates used in this experiment with short-cycle plants such as bedding plants in compared to use of WSF. Except for the bottom placement treatment, the use of 8–9 month CRF resulted in generally less nutrients leached than WSF.