Use Of Controlled-release Fertilizers Research Articles

FERTILIZAÇÃO DE LIBERAÇÃO CONTROLADA NO CRESCIMENTO INICIAL DE ANGICO-BRANCO

O uso de fertilizantes de liberação controlada constitui-se em uma das modernas técnicas na produção de mudas. Porém, existem poucos relatos de seus efeitos sobre o crescimento em espécies florestais nativas. Objetivou-se testar doses crescentes de fertilizante de liberação controlada no crescimento inicial de mudas de angico-branco. As mudas foram originadas de sementes, semeadas em tubetes (110 cm3), contendo substrato à base de casca de pínus e vermiculita. O experimento foi conduzido no delineamento inteiramente casualizado com parcelas subdivididas no tempo, sendo os fatores constituídos por seis doses de Osmocote® (testemunha, 1000, 2000, 3000, 4000 e 5000 mg dm-3 de substrato) e por cinco épocas de avaliação (0 - instante da germinação, 15, 35, 65 e 95 dias após a germinação). Foram avaliadas as seguintes características, em cada época: altura; número de folhas; número de nós; diâmetro; relação altura/diâmetro; comprimento total do sistema radicial; volume da raiz e matéria seca da raiz; caule; folha; parte aérea e total. Ao longo de 95 dias de cultivo, a fertilização testada influenciou a maioria das características de crescimento. A dose próxima a 2000 mg dm-3 de fertilizante correspondeu aos maiores valores médios para as características do número de folhas, diâmetro e matéria seca das mudas. A maior altura correspondeu à dose de 2743 mg dm-3, e a relação altura/diâmetro à dose de 3544 mg dm-3. Contudo, o comprimento total e o volume do sistema radicial, responderam negativamente ao sistema de adubação utilizado.

Drought response of dry-seeded rice to water stress timing and N-fertilizer rates and sources

Dry seeding has been identified as an option for increasing cropping intensity and productivity in rainfed ricelands. Managing drought and nutrients are important for increasing yield, but the interactive effects of drought and nutrients on dry-seeded rice (Oryza sativa L.) growth have not been systematically investigated. Two experiments were carried out in 1994 and 1995 to analyze the effects of N fertilizer rate and the use of controlled-release fertilizers (CRFs) on the growth and yield of dry-seeded rice grown on a silty clay loam (Typic Tropaquept) subjected to water stress at different crop stages. In both years, in the main plots, rice was subjected to water stress at four different stages of development. The subplots were designed to compare the effect of the application of prilled urea and CRFs Osmocote (1994) and Polyon 12 (1995). Four N rates (0, 60, 120 and 180 kg ha−1) were imposed on rice in the sub-subplots (1994 only). The N fertilizer source did not affect any of the measured parameters. Irrespective of the N the fertilizer rates, grain yield and total dry matter accumulation of rice plants stressed at the flowering stage (WSFL, 1994) and panicle initiation stage (WSPI, 1995) were significantly lower than those of well-watered plants and plants stressed at the vegetative stage. Water stress during the grain-filling stage reduced the grain yield in 1995 when the stress was severe. Application of N fertilizer increased the yield compared with zero N in all water treatments, except for the WSFL plants whose yield did not change. The WSFL treatment also significantly reduced agronomic N-use efficiency.

Controlled-release Fertilizers for Vegetable Production in the Era of Best Management Practices: Teaching New Tricks to an Old Dog

Best management practices (BMPs) for vegetable crops are under development nationwide and in Florida. One goal of the Florida BMP program is to minimize the possible movement of nitrate-nitrogen from potato (Solanum tuberosum) production to surface water in the St. Johns River watershed without negatively impacting potato yields or quality. Current fertilizer BMPs developed for the area focus on fertilizer rate. Controlled-release fertilizers (CRF) have long been a part of nutrient management in greenhouse and nursery crops. However, CRFs have been seldom used in field-vegetable production because of their cost and release characteristics. Nutrient release curves for CRFs are not available for the soil moisture and temperature conditions prevailing in the seepage-irrigated soils of northern Florida. Controlled-leaching studies (pot-in-pot) in 2000 and 2001 have shown that plant-available nitrogen (N) was significantly higher early in the season from ammonium nitrate, calcium nitrate and urea compared to selected CRFs. However, N release from off-the-shelf and experimental CRFs was too slow, resulting in N recoveries ranging from 13% to 51%. Cost increase due to the use of CRFs for potato production ranged from $71.66 to $158.14/ha ($29 to $64 per acre) based on cost of material and N application rate. This higher cost may be offset by reduced application cost and cost-share pro-grams. Adoption of CRF programs by the potato (and vegetable) industry in Florida will depend on the accuracy and predictability of N release, state agencies' commitment to cost-share programs, and CRFs manufacturers' marketing strategies. All interested parties would benefit in the development of BMPs for CRFs.

Produção de mudas de espécies arbóreas nativas com combinações de adubos de liberação controlada e prontamente solúveis

O objetivo deste estudo foi testar diversas doses e fontes de adubo para verificar o crescimento de mudas de cinco espécies arbóreas nativas. As espécies utilizadas foram as pioneiras Guazuma ulmifolia (mutambo) e Croton floribundus (capixingui), as secundárias iniciais Peltophorum dubium (canafístula) e Gallesia integrifolia (pau-d'alho) e a clímax Myroxylon peruiferum (cabreúva). Os tratamentos consistiram principalmente na utilização de adubo de liberação controlada (ALC, 19-06-10, N-P2O5-K2O) de maneira pura ou em mistura com adubo em pó (AP, 14-16-18), ou AP mais adubação de cobertura periódica (ACP, 19-06-20), comparados com adubação convencional (adubação de base mais adubação de cobertura com sulfato de amônio e cloreto de potássio) e testemunha (sem adubação). O substrato utilizado foi composto por 60% de húmus de minhoca, 30% de casca de arroz carbonizada e 10% de terra de subsolo, em base volumétrica. O recipiente que comportou o substrato foi o tubete de polipropileno de 50 cm³ de capacidade. Entre os tratamentos que produziram mudas de boa qualidade ao final do experimento, para cada espécie, aqueles com doses de 3,2 e 4,8 kg de adubo de liberação controlada por metro cúbico de substrato foram comuns a todas as espécies e, adicionalmente, resultaram em dimensões apropriadas para plantio no campo em menor tempo do que os outros tratamentos.

Fertilizer Source and Irrigation System Affect Geranium Growth and Nitrogen Retention

Pelargonium ×hortorum Bailey `Pinto Red' plants were fertilized with equal amounts of N, P, and K derived from: 1) 100% constant liquid fertilization (CLF); 2) 50% CLF plus 50% controlled-release fertilizer (CRF); or 3) 100% CRF per pot and irrigated using hand (HD), microtube (MT), ebb-and-flow (EF), or capillary mat (CM) irrigation systems. The treatment receiving 100% CRF produced greater total dry weights, and released lower concentrations of NO3-N, NH4-N, and PO4-P in the run-off than the 100% CLF treatment. The percentage of N lost as run-off was greatly reduced with the use of CRF. MT irrigation produced the greatest plant growth and HD irrigation produced the least. The EF system was the most water efficient, with only 4.7% of water lost as run-off. Combining the water-efficient EF system with the nutrient-efficient CRF produced the greatest percentage of N retained by plants and medium (90.7) and the lowest percentage of N lost in the run-off (1.7).

Response of Lettuce to Water and Nitrogen on Sand and the Potential for Leaching of Nitrate-N

The low desert region of Arizona is the major area of lettuce (Lactuca sativa L.) production in the United States during the winter. Lettuce is commonly grown on the loam, clay loam, and clay soils of the alluvial river valleys. There is some interest in moving a portion of the vegetable production onto the sandy soils of the terraces (mesa) above the alluvial river valley to partially relieve the intensive production pressure being placed on lands in the valley. Of major concern in these sandy soils is water and N management. Studies were conducted during two seasons to evaluate the response of crisphead lettuce to sprinkler irrigation and N fertilizer and to evaluate the potential for leaching of nitrate-N on a coarse-textured soil. Lettuce yields increased in response to water and N, and were maximized by 55 cm of water and 271 kg·ha–1 N in 1991–92 and 76 cm water and 270 kg·ha–1 N in 1992–93. These water and N rates exceeded those typically required on finer-textured alluvial valley soils. At N and water rates required for maximum yields, 88% and 77% of the applied N was not recovered in the aboveground portions of the plant during the 1991–92 and 1992–93 seasons, respectively. Overall, data for the amount of N fertilizer not recovered, estimates of nitrate-N leaching determined during one growing season, and analysis of soil samples collected after harvest indicate the potential for large N leaching losses on this coarse-textured soil. Alternative production methods that enhance water and N use efficiencies, such as drip irrigation and/or the use of controlled-release fertilizers, should be considered on this sandy soil.

Using Nutrient Uptake Patterns to Develop Efficient N Management Strategies for Vegetables

Nitrogen in a soil that is not immediately taken up by a crop is subject to leaching, denitrification, and other mechanisms of loss. Generally, split applications of N throughout the growing season reduce the potential for N loss compared to a single preplant application. Timing of N application should account for the characteristic N uptake patterns of the crop and the lag time between application of fertilizers and plant availability. N uptake studies allow one to identify total amount of N accumulated by the crop and periods of peak nitrogen demand. This information can then be used to devise management strategies aimed at supplying N preceding anticipated N uptake. Split sidedress N application, fertigation, and the use of controlled-release fertilizers are all viable options, depending on the crop production scenario and available infrastructure.

Use of controlled-release fertilizers for young citrus trees

The effects of several controlled-release fertilizer compounds were compared with those of a soluble fertilizer mixture on young citrus trees growing in sandy soils under a subtropical environment. Soluble fertilizers were found to be more readily available and had shorter residual effects on leaf and soil N and K than controlled-release fertilizers. The high rate Osmocote (Sierra) treatment gave the highest leaf Mg content in 1988, probably because MgO was included in Osmocote, while MgSO 4 was used in the other fertilizer formulations. In 1988, Osmocote treatments gave the highest leaf Fe concentrations, which could be attributed to the high Fe content in the Osmocote fertilizer. No difference in tree growth was found among soluble and controlled-release fertilizer treatments. Soluble fertilizers produced smaller size fruit and yielded less fruit than controlled-release fertilizers, but the differences in fruit yield were not significant. The lack of significance in fruit yield and in most fruit quality parameters between the soluble and controlled-release fertilizer treatments could be attributed to the highly variable data because it was the first fruit crop. Controlled-release fertilizers were very promising for sandy soils and subtropical environments as they can be applied in smaller amounts and less often than soluble fertilizers, without adverse effects on tree growth or fruit production and quality.

Evaluation of Controlled-release Fertilizers for Young Citrus Trees

Controlled-release sources of N and K were compared with soluble sources on young `Valencia' orange trees (Citrus sinensis [L.] Osb.). The effects of these fertilizers on leaf mineral concentration, soil chemical analysis, and tree growth were evaluated for 3 years. Soluble fertilizers were generally more readily available but had shorter residual effects on leaves and soil than controlled-release fertilizers. In the top 30 cm of soil, the plots treated with controlled-release N had 23% more total N than those treated with soluble N sources, while the plots fertilized with controlled-release K contained 56% more extractable K than those that received soluble K. Different effects on leaf and soil N between the two controlled-release N sources, sulfur-coated urea (SCU) and methylene urea (MU), were also found. With the use of controlled-release fertilizers, application frequency was reduced from a total of 15 to six applications with no adverse effects on tree growth, leaf mineral composition, or soil fertility during the first 3 years. Combining soluble and controlled-release fertilizers in a plant nutrition program offers an economical and effective strategy for citrus growers.