Frequency Of Fertilizer Application Research Articles

Pengaruh Konsentrasi dan Frekuensi Pemberian Pupuk Organik Cair Terhadap Pertumbuhan Tanaman dan Produksi Sawi Samhong (Brassica juncea L.)

In mustard cultivtion, the right combination of the concentration of liquid organic fertilizer given through the leaves and the frequency of application are factors that can optimize growth and yield. This research aimed to test the effectiveness of the concentration and frequency of NASA liquid organic fertilizer on the growth and yield of Samhong mustard (Brassica juncea L.). The research was carried out in the greenhouse of the Faculty of Agriculture, Pattimura University, Ambon. This research was conducted as an experiment using a Randomized Block Design with 2 factors. The first factor was the concentration of NASA liquid organic fertilizer which consisted of 4 levels, namely: concentration of 0 mL/L of water (without giving POC); 4 mL/L of water; 8 mL/ mL/L of water; and 12 mL/L of water. The second factor was the frequency of fertilizer application which consists of 3 levels, namely 6 times, 3 times and 2 times of application. There were 12 treatment combinations, with 3 replications, so there were 36 experimental units. The research results showed that the concentration of NASA liquid organic fertilizer had a very significant effect on plant height, number of leaves, leaf area, plant fresh weight, plant dry weight and root dry weight. A concentration of 8 mL/L of water was the best concentration for plant fresh weight, namely 323.89 g. For the treatment of frequency of application, there was a very significant effect on the number of leaves, leaf area, plant fresh weight, plant dry weight and root dry weight, with a frequency of 3 applications being the best frequency for the growth and yield of Samhong mustard greens. The interaction between NASA liquid organic fertilizer concentration and application frequency did not significantly effect all observed variables.

Growth and yield response of Watani Wado job's tears (Coix lacryma-jobi L.) to the application frequency of phosphate fertilizer and paclobutrazol in different growing seasons

Job's tears (Coix lacryma-jobi L.) is a carbohydrate source functional food crop that can be developed as a substitute for rice. This study aims to determine the best application frequency of phosphate (P) fertilizer and paclobutrazol for supporting the growth and yield of job's tears in both rainy and dry seasons. The research was conducted from November 2021 - November 2022 at the Ciparanje research station and Laboratory Centre Universitas Padjadjaran, Jatinangor, Sumedang. The experiment used a randomized block design (RBD) consisting of P fertilizer application frequency (once, twice, and thrice) and paclobutrazol application frequency (once, twice, and thrice) and three replications.. The best season was determined using the T-test. The results showed that there was no interaction between growth components and job's tears yield in both rainy and dry season planting. P fertilizer application had a significant effect on lateral branch per tiller in the rainy season and root-shoot ratio in the dry season. Paclobutrazol application had a significant effect on the number of tillers per plant and number of seeds per plant in the rainy season, and the lateral branch per tiller in the dry season. Planting in the rainy season had the best growth and yield components compared to the dry season.

Knowledge level of pomegranate growers about recommended pomegranate production technologies of UAS Dharwad

The present study was conducted with specific objective to study the knowledge level of pomegranate growers about recommended pomegranate production technologies in Vijayapura and Bagalkot districts of Karnataka, respectively. Total of 8 villages were selected for the study and 15 pomegranate growing farmers from each village were randomly selected to constitute a total sample of 120 farmers. It was noticed that almost two fifth (39.17 %) of the pomegranate farmers belonged to medium knowledge level category, 32.50 per cent of them belonged to low knowledge level category and 28.33 per cent of them belonged to high knowledge level category, respectively. Cent per cent of the pomegranate growers had knowledge about the varieties, planting material, spacing, time of planting, frequency of pruning and mode of irrigation. Large majority of them had knowledge about chemicals to control pests (90.00%), size of the pit (85.00 %), chemicals to control diseases (80.00 %) and diseases of pomegranate (78.33 %). Majority of them had knowledge about the type of soil (71.67%), frequency of fertilizer application (66.67%) and pests of pomegranate (60.00 %). More than half (59.17 %) of them had knowledge about the frequency of irrigation and Bahar treatment (55.83 %). About 45.83 per cent of them had knowledge about the pit filling process with FYM, 43.33 per cent of them had knowledge about the growth regulators used, 41.67 per cent of them had knowledge about the proportion of NPK application per tree and 39.17 per cent of them had knowledge about the rest period given during Bahar treatment. Equal percentage of them (33.33 %) had knowledge about types of Bahar treatments and average yield per tree. About 30.83 per cent of knew about the quantity of FYM application and 23.33 per cent knew about intercropping in pomegranate and 19.16 per cent of them knew about the weedicides.

Optimizing Fertilizer Management Practices in Summer Maize Fields in the Yellow River Basin

This study aims to examine the impact of combined irrigation and fertilizer control on the summer maize yield, nitrogen use efficiency (NE), and nitrogen leaching (NL) in the Yellow River Basin. Based on the measured data from the field summer maize experiment in 2021 and 2022, a water-nitrogen movement model was constructed for ‘Zhengdan 958’ maize under two irrigation methods (wide furrow irrigation (G) and border irrigation (Q)), three fertilizer rates (120 kg/ha (N1), 220 kg/ha (N2), and 320 kg/ha (N3)), and three fertilizer frequencies (1 (T1), 2 (T2), and 3 (T3)), yielding 18 total treatments. Calculation of nitrogen leaching was based on water nitrogen transport modeling. The study then analyzed the factors and their combined effects. A multi-objective optimization genetic algorithm (NSGA-II) was established to evaluate maize yield, nitrogen use efficiency, and nitrogen leaching. The results indicate that the determination coefficients between simulated and measured water, nitrogen values exceeded 0.74. The rate optimized HYDRUS model effectively simulated the soil solute movement. The interaction of the irrigation method, fertilizer rate, and fertilizer application frequency did not significantly affect yield and nitrogen leaching, but did significantly impact nitrogen use efficiency (p < 0.05). Nitrogen leaching increased gradually as nitrogen application increased. The yield under wide furrow irrigation was 6.26% higher than that under border irrigation. The optimal coupling scheme of water and fertilizer was obtained using the genetic algorithm multi-objective optimization method, where the combined GN2T2 treatment was the optimal management model, the summer maize yield reached 14,077 kg/ha, nitrogen use efficiency and nitrogen leaching were reduced to 30.21 kg·kg−1 and 17.64 kg/ha, respectively. These findings can guide summer maize cultivation in the Yellow River Basin and assist in reducing nitrogen surface source pollution.

Increasing The Growth and Yield of Lowland Rice (Oryza Sativa L.) with Optimum Dosage and Frequency of Potassium

Lowland rice is a commodity crop that is very influential in the survival of many people, especially inhabitants in most Asian countries, especially Indonesia. Rice is the staple food of Indonesian people, the shortage of which can result in complications for the country. In connection with this food security issue, it is necessary to make efforts to prevent food shortages. The national production capacity of rice must be increased. The long-term goal is to increase the productivity of rice plants to support Indonesia towards rice self-sufficiency. This study has a short-term objective, namely, to determine the effect of potassium fertilizer and to obtain the best dose on the growth and production of rice plants. This was a factorial experiment using a completely randomized design (CRD) with two factors: the KCl fertilizer dosage and the frequency of fertilizer application. The results showed that the best treatment was with a potassium fertilizer dosage of 150 kg ha-1 with a frequency of 2-time fertilizer application.

Mineral nutrition in orchids

The Orchidaceae family stands out when it comes to the commercialization of pot flowers, this is due to their flowers being widely attractive and have variability of colors, size and shapes according to the species; this results in plants with high relevance to the economy in the floriculture sector. The goal of this study was to elucidate questions about the effect of micronutrients on initial growth, the influence of electrical conductivity and frequency of fertilizer application, and the efficiency of organic fertilization with castor bean cake, on the growth and nutrition of Brassia verrucosa Lindley orchid. Studies with mineral fertilization involving nitrogen (N), phosphorus (P) and potassium (K) in Cattleya and Phalaenopsis seedlings allowed to obserevar that the N increment increased the number of flowers in Cattleya, while P and K did not affect this variable. The salinity of irrigation water also has an effect on growth and flowering. The electrical conductivity, the sources of fertilizers, their interaction with the substrate, the balance between the nutrients, the quantities and frequencies to be used, in addition to the different phenological requirements and characteristics intrinsic to the species, are important aspects to be considered in fertirigation.

Soil Enzyme Activities Associated with Differential Outcomes of Contrasting Approaches to Soil Fertility Management in Corn and Soybean Fields

Sustainable agricultural practices such as reduced tillage and optimized fertilization may have potential to improve soil health and increase availability of plant nutrients and yields. However, there is very little information relating soil quality or health to crop productivity, particularly under farmer management. Therefore, the objective was to investigate the effects of two contrasting approaches to crop fertility management on crop productivity, soil test measurements, and soil enzyme activity as integrative measures of soil health. A three year study was conducted at on-farm sites in Ohio, Illinois, and Iowa where topsoil (0-15 cm) and crop yield of Zea mays L. (corn) and Glycine max. (L.) Merr. (soybean) rotations were collected from two contrasting fertility management systems. The two contrasting approaches tested were the Maximum Farming System (MFSyst) and a more Conventional system (Conv) that differ in approaches to tillage and the frequency of fertilizer applications during the growing season. The MFSyst approach resulted in significantly higher yields, soil nutrient test levels along with β-glucosidase (GLU) and arylsulfatase (ARYL) which are sensitive soil health indicators. Nitrogen use efficiency (NUE) of corn was significantly elevated by nearly 18%, corn yield correlated with GLU activities, and soil test phosphorous (P) levels were reduced by over 50% using the MFSyst approach. These results indicate that improvements in soil health detected by soil GLU and ARYL enzyme activities are associated with significant improvements in soil quality and crop productivity.

Enhancement of Drought Tolerance in Patchouli (Pogostemon cablin, Benth) by Modifying Micro Climate and Frequency of Fertilization

Drought stress is one of abiotic stresses and has caused a significant deterioration in growth and yield of patchouli. This research was conducted in Reuleut Timu Village, Muara Batu District, Aceh Utara Regency, from July to December 2016, using split plot design in a Randomized Block Design with three replications. The main plot was mulch treatments (without mulch, rice straw mulch and black silver plastic mulch). The subplots were treated with different frequency of fertilizer application (once, twice and three times). The results revealed that the application of rice straw mulch has reduced the effects of drought stress, suppressed the soil temperature fluctuations, maintained soil moisture, which resulted in an increase of patchouli growth. Different frequency of fertilizer application did improve the oil yield, proline accumulation and drought resistance.

Internal Versus Edge Row Comparison in Jajar Legowo 4:1 Rice Planting Pattern at Different Frequency of Fertilizer Applications

Jajar legowo 4:1 cropping pattern has been adopted by rice farmers; however, there has been limited information on the comparison between internal and edge rows. In addition, the effects of timing and frequency of fertilizer applications on rice cultivated at riparian wetland also have to be understood. In this research, both single and split applications of fertilizer were employed. The single fertilizer applications were applied at 15 days after transplanting (DAT) (T1), 30 DAT (T2), 45 DAT (T3); and the split applications were 15+30 DAT (T4), 15+45 DAT (T5), 30+45 DAT (T6), and 15+30+45 DAT (T7). Results of this research indicated that crops in the edge rows produced higher leaf area index but those at internal rows produced higher dry weight biomass. Split fertilizer application to three times (T7) increased the weight of grains and number of filled spikelet but did not affect other shoot and root growth traits. Overall, fertilizer application increased leaf chlorophyll and nitrogen content. Jajar legowo 4:1 planting pattern and split fertilizer application to three times are recommended for increasing yield in rice cultivated at riparian wetlands.

Soil Biochemical Properties and Nutrient Leaching from Smallholder Oil Palm Plantations, Sumatra-Indonesia

The study aimed to assess soil biochemical properties and nutrient leaching in palm oil plantation. The research was conducted in smallholder oil palm plantations which were located in Jambi Province - Indonesia. Nutrient leaching was determined by measuring nutrient concentration in soil solution bi-weekly and monthly in the frond stacked and fertilized areas; soil water samples were collected by using suction cup lysimeter. The result showed that the application of mineral fertilizer (e.g. NPK) and dolomite resulted higher base saturation, exchangeable Ca, and available P in the fertilized than frond stacked and inter row areas (p ≤ 0.05). Stacking palm oil frond increased the soil macro-porosity, hence decreased leaching of K, Mg, Na, P, and total Al in the frond stacked than in the fertilized areas. The lower leaching losses and the higher soil macroporosity in the frond stacked than in the fertilized areas indicated that either the water did not dilute nutrient in the soil due to bypass flow, or the nutrient release from mineralization did not surpass nutrient demand which is quickly uptaken by palm root. Proper soil management through synchronizing rate of fertilizer application with nutrient output or frequency of fertilizer application may potentially minimize leaching losses.

PENGARUH KONSENTRASI DAN FREKUENSI APLIKASI PUPUK URINE SAPI TERHADAP PERTUMBUHAN DAN PRODUKSI TANAMAN CABAI KERITING (Capsicum annuum L.)

Red chili plant a bush-shaped plant and is widely used as a flavor enhancer in food spicy . Demand for the chili continue to increase in line with population growth. This research was conducted at the location of Farmers Group Source Rezeki, Toddopulia Village, District Tanralili Maros which lasts from March to June 2016. This study aims to analyze the effect of the concentration and frequency of urine sapii applications on the growth and yield of curly red pepper. This study was conducted using a randomized block design with factorial 2 factors. The first factor is the treatment of cow urine concentration consisting of three levels ie 20 ml / liter of water, 40 ml / liter of water, and 60 ml / liter of water. The second factor is the frequency of application of cow urine which consists of two levels ie 2 weeks and 4 weeks. The results showed that the concentration of 40 ml / liter of water and frequency of fertilizer application of cow urine in 2 weeks give better effect on the growth and yield of chilli curls with the highest plant height of 85.83 cm, the number of branches stalk 44.42, the fastest flowering age 46 02 days, the number of fruit per plant fruit 143.62, weighs 625.42 grams of fruits per plant and fruit production per hectare of 11.47 tonnes.

EFFECTS OF TYPES OF MEDIA AND NPK FERTILIZER ON THE ROOTING CAPACITY OF CHRYSANTHEMUM CUTTINGS

Physiological status of chrysanthemum cuttings during rooting process highly influences plant growth and flower production. Amongst other aspects, rooting capacity of the cuttings is the most important. Rooting capacity is influenced by environmental conditions such as growing medium and nutrition. The study was aimed to analyze the effects of different types of media, fertilizer concentration, and frequency of fertilizer application on the rooting capacity of chrysanthemum cuttings. The experiment was conducted at the Segunung Experimental Station of the Indonesian Ornamental Crops Research Institute from February to May 2005. The treatments consisted of four different rooting media, i.e. carbonized rice husk, coco peat, perlite, and mixture of perlite and vermiculite (1:1 v/v); two concentrations of NPK (25:7:7) fertilizers, i.e. 1.75 and 2.5 g 1-l; and four frequencies of fertilizer application, i.e. every 1 day, 2 days, 3 days, and 4 days. The experiment was designed in a completely randomized block with four replications. Parameters observed were rooting capacity and cutting performances such as cutting height, cutting diameter, number of leaves, number of visible roots, and root length at 16 days after planting. The results showed that chrysanthemum cuttings rooted in carbonized rice husk had better performance than those rooted in coco peat, vermiculite, and mixture of perlite + vermiculite. Higher concentration of fertilizer solution up to 2.5 g l-1 also gave significant effect on the root formation and further root growth of cuttings. However, the rooting capacity of cuttings was not affected by the frequency of fertilizer application. This study implied that carbonized rice husk growing medium supplemented with NPK (2.5 g l-l) every 4 days during rooting period is the choice for traditional chrysanthemum growers to increase the perform-ance and quality of the cut flowers.

EFFECTS OF TYPES OF MEDIA AND NPK FERTILIZER ON THE ROOTING CAPACITY OF CHRYSANTHEMUM CUTTINGS

Physiological status of chrysanthemum cuttings during rooting process highly influences plant growth and flower production. Amongst other aspects, rooting capacity of the cuttings is the most important. Rooting capacity is influenced by environmental conditions such as growing medium and nutrition. The study was aimed to analyze the effects of different types of media, fertilizer concentration, and frequency of fertilizer application on the rooting capacity of chrysanthemum cuttings. The experiment was conducted at the Segunung Experimental Station of the Indonesian Ornamental Crops Research Institute from February to May 2005. The treatments consisted of four different rooting media, i.e. carbonized rice husk, coco peat, perlite, and mixture of perlite and vermiculite (1:1 v/v); two concentrations of NPK (25:7:7) fertilizers, i.e. 1.75 and 2.5 g 1-l; and four frequencies of fertilizer application, i.e. every 1 day, 2 days, 3 days, and 4 days. The experiment was designed in a completely randomized block with four replications. Parameters observed were rooting capacity and cutting performances such as cutting height, cutting diameter, number of leaves, number of visible roots, and root length at 16 days after planting. The results showed that chrysanthemum cuttings rooted in carbonized rice husk had better performance than those rooted in coco peat, vermiculite, and mixture of perlite + vermiculite. Higher concentration of fertilizer solution up to 2.5 g l-1 also gave significant effect on the root formation and further root growth of cuttings. However, the rooting capacity of cuttings was not affected by the frequency of fertilizer application. This study implied that carbonized rice husk growing medium supplemented with NPK (2.5 g l-l) every 4 days during rooting period is the choice for traditional chrysanthemum growers to increase the perform-ance and quality of the cut flowers.

Ectomycorrhizal community structure and function in interior spruce forests of British Columbia under long term fertilization

Long-term fertilization is being considered as a mechanism to increase growth of pine and spruce trees in British Columbia following a major outbreak of mountain pine beetle. It is important, however, that long-term fertilization not disrupt colonization by ectomycorrhizal fungi or impede their ability to release nutrients from soil organic matter. In order to determine the effect of long-term (up to 14years) fertilization on the structure and function of ectomycorrhizal (ECM) fungal communities on roots of interior spruce, we characterized the ECM fungal community and, on separate samples collected at a different time of year, assayed for extracellular enzymes in the mycorrhizoplane. The study was conducted at three interior spruce (naturally occurring hybrids of Picea glauca [Moench] Voss and Picea engelmannii Parry) plantations in the interior of south-central British Columbia. Three 0.164ha plots per site received no (controls), periodic (200kgha−1N, plus P, K, S, Mg, and B every 6years), or annual (same nutrients adjusted to maintain foliar N concentration at 1.3% and other nutrients in balance; 50 to 75kgha−1 of N, depending on site and year) fertilization. There was no overall effect of fertilization on the composition of the ECM fungal community (OTUs) on spruce roots (permutational MANOVA P=0.4) nor on alpha diversity per plot. At single sites, there was reduced relative abundance of Cortinarius spp. mycorrhizas under periodic fertilization, and increased relative abundance of Lactarius spp. or Tylospora spp. mycorrhizas under annual fertilization. None of the dominant genera increased or decreased significantly across sites. The ratio of carbon-acquiring to mineral nutrient-acquiring enzyme activities in the mycorrhizoplanes increased with frequency of fertilizer application. Increased litterfall may explain the increase in plant cell wall-degrading enzyme activity in fertilized plots. A decrease in activities involved in the release of sulphur was as expected in fertilized plots because the fertilizer contained inorganic nitrogen, phosphorus and sulphur. Although activities of two enzymes involved in nutrient cycling (sulfatase and phosphomonoesterase) tended to decrease, there did not appear to be an overall loss of organic matter-degrading potential from the ECM fungal community on spruce roots under long-term fertilization.

The effect of fertilizer amendment on diesel biodegradation in contaminated soils

Diesel biodegradation and the effect of application frequency were investigated in artificially contaminated soils (loam soil and sea sand) amended with commercial fertilizers and the effect of application frequency. Two sets of four equal portions (2 kg each) of diesel-contaminated soils were amended with 10% (w/w) of 2 different commercial fertilizers at 4 different but regular intervals for up to four times during a 7-week study period. The microcosms were then incubated at 30°C and sampled weekly. One sterilized soil microcosm contaminated with 10% (v/w) diesel and supplemented with 10% (w/w) fertilizer and one naturally attenuated microcosm served as controls. The amount of diesel remaining in each sample was determined using the Soxhlet extraction method and compared to the amount of diesel present in the same sample at day 0. The quantities of hydrocarbon contents in the supplemented samples and the controls were determined by GC-MS. The total heterotrophic population of each sample was also monitored. The population increase was found to correspond to the higher diesel degradation percentage in the study on sea sand. A significant enhancement (p<0.05) of diesel degradation was observed after the supplementation of fertilizers especially in sea sand compared with those in both controls. There were no significant differences in diesel degradation with the fertilizer application frequency. In conclusion, supplementation of diesel contaminated soils with commercial fertilizer results in a significant increase on diesel biodegradation. Additional supplementation did not further stimulate the degradation under the same conditions. Key words: Diesel, bioremediation, fertilizers, application frequency.

Pengaruh Waktu dan Frekuensi Aplikasi Pupuk Daun Terhadap Pertumbuhan dan Pembungaan Anggrek Dendrobium ’Tong Chai Gold’

&lt;p&gt;ABSTRACT&lt;/p&gt;&lt;p&gt;&lt;br /&gt;Most of orchids grow slowly. Low fertilizer concentration with high frequency of fertilization can be the alternative to increase orchids growth. The objective of the research was to evaluate the effect of time and frequency of fertilizer application on Dendrobium ‘Tong Chai Gold’. The experiment was arranged in &lt;br /&gt;randomized of completely block design with two factor of treatment. The first factor is time of application and the second one is frequency of application of foliar fertilizer. The time applications in the morning about 6.30 to 7.30 &lt;br /&gt;o’clock, at mid day about 11.30 to 12.30 o’clock, and in the afternoon about 16.30 to 17.30 o’clock. The frequency of foliar fertilizer application were every three days or six days. The result of this experiment showed that time and frequency application of foliar fertilizer could not increased number of bulb, but increased young leaf length, and width. Fertilizer was applied in the morning combined with every three days frequency of fertilizer tended to result a better flowering of Dendrobium ‘Tong Chai Gold’.&lt;/p&gt;&lt;p&gt;&lt;br /&gt;Key words : Dendrobium, fertilizer, application time and frequency, growth, flowering,&lt;/p&gt;

Response of Maize and Cowpea Grown Sequentially to Application of Phosphate Rock in the Humid Tropics

Field trials were conducted at the Institute of Agricultural Research and Training Ibadan in 2000 and 2001 cropping seasons to evaluate the efficiency of some phosphorus (P) sources, rates, and frequency of application on grain yields of maize and cowpea grown sequentially. The experiment was laid out in a split–split plot arrangement using randomized complete block design, with three replications. The main plot was frequency of fertilizer application (seasonal and annual). Source of P [single superphosphate (SSP: 18% P2O5)]; Ogun rock phosphate (OPR: 20.21% P2O5), and crystallizer super (CS: 31.4% P2O5) constituted the subplots. The P rates (0, 20, 40, and 60 kg P ha−1) were the sub-subplots. An early maize cropping followed by a late-season cowpea was the sequential cropping, while an early maize followed by a late-season maize was the continuous cropping. The croppings were repeated the second year. Frequency of P application and source of P were significantly different while rates of application were not. Maize and cowpea grain yields from the control treatment were significantly less than yields from P-treated plots. Maize grain yields were slightly greater in plots alternated with cowpea, compared to continuous maize. Relative agronomic efficiency (RAE) values of OPR and CS were 67% and 75%, respectively, in annual application and 140% and 134% in seasonal applications, respectively, in 2000. In 2001, the trend was almost similar to 2000 except that there was a decline in RAE values of cowpea. Each Naira invested in the annual application returned about ₦3.12 while about ₦2.13 was returned with the seasonal application (₦125.00 is the equivalent of USD$1.00). The OPR and CS can serve as alternatives to water-soluble sources such as SSP.

The Nutrient Profile in Organic Fertilizers

In order to manage nitrogen (N) and phosphorous (P) through organic fertilization in aquaculture ponds, it is important to understand the nutrient profile of different animal manures at various concentrations and the respective biological response. The rate of nutrient released from animal manure over time is a key factor in deciding the frequency and quantity of manure required to fertilize ponds. This study was conducted to elucidate the nutrient profile, and its efficiency in terms of primary productivity, of pig, cow, and buffalo manure, at different N:P concentrations in tank. Appropriate concentrations were maintained by using the minimum amount of inorganic fertilizer supplement. This paper also investigated the impact of lime-treated manure, a traditional practice in Vietnam, on primary production (phytoplankton abundance). The average nitrogen (N) and phosphorus (P) content was higher in pig manure (0.54% N and 0.173% P) compared to cow (0.31% N and 0.028% P) and buffalo (0.34% N and 0.013% P). The ammonia release rate increased with increase in N concentration. The average ammonia release rate (all concentrations, 1-2 ppm N) in the pig manure treatment was significantly higher than cow and buffalo manure treatments. Cow and buffalo manures were found to be similar in terms of ammonia release rate. However, soluble phosphorus level was significantly lower in buffalo manure treatments compared with cow manure. The pig manure treatment produced maximum soluble phosphorus levels in the tanks. The primary productivity obtained at various concentrations (1-2 ppm N:0.5 ppm P) did not differ significantly (P > 0.05) in cow and buffalo manure treatments. The primary productivity performance of pig manure was highest amongst the manure types tested. The 1 ppm N:0.5 ppm P concentration from pig manure yielded the maximum average (1.64 mg C/L) net primary productivity. Based on the primary productivity pattern in the tank, which had a significant correlation with nutrient release rate for all manures tested, the frequency of fertilizer application appeared to be most suitable every 8-10 days. However, increasing the frequency of manure application based on the level of nutrient available in the water will provide more control on nutrient and water quality management for pond aquaculture systems. This level of monitoring may not be practical for regional farmers.

Pond Fertilization Regimen

ABSTRACT Pond fertilization has assumed an important role to supplement nutrient deficiency and augment biological productivity through autotrophic and heterotrophic pathways. This is especially important in the extensive and semi-intensive culture systems by promoting the functioning of natural ecosystems in a benign environment. The composition of inorganic and organic fertilizers forms the basis for selection of dose and quality of fertilizer application. While inorganic fertilizers produce perceptible results within a short period, organic manure is extremely cheap and is of considerable significance in developing countries. Nitrogen demand in fish ponds can be compensated through nitrogen fixation, as well as from accumulated humus from bottom sediments, especially from old fish ponds. The frequency of fertilizer application should be economical, though it is accepted that the lower the frequency, the better the productivity. In aquaculture ponds, the optimum N:P ratio was suggested between 4:1 to 8:1, whereas the optimum C:N ratio for composting was between 20 and 40. The exchange properties and equilibrium phosphorus concentration between soil and water influence water quality, nutrient status, and primary productivity of the pond ecosystem. These act as buffers to stabilize environmental conditions in ponds. Pond soils may exert negative influence on aquaculture production if one or more of their properties are outside the optimum range for aquaculture. The present study reviews state-of-the art pond fertilization in relation to the role of pond soils; different inorganic fertilizers such as phosphorus (P), nitrogen (N), potassium (K); fertilizer dose and frequency; P:N ratio; organic manure; aquatic food web; optimal manuring; decomposition of organic manures; mineralization; production efficiency; and limitations of organic manures. More studies on pond fertilization in the context of nutrient dynamics and fertilizer-microbial interactions under different agroclimatic regions are necessary for an effective, appropriate, and economic fertilization program. The environmental consequences of overfertilization resulting in pollution and subsequent hazards to public health should be taken into consideration.

PLANTER SOILS IN HONG KONG: II. FLUXES OF NITROGEN AND PHOSPHORUS

Summary N and P fluxes in different planter or container soils were investigated by the in situ core incubation technique over a period of one year, with special emphasis on their seasonal fluctuations and the effect of management intensity. The planter soils were located in Central Kwun Tong and Wo Che, representing the commercial, industrial and residential areas of urban Hong Kong. The objectives of this study were threefold: (1) to examine the mineralization of N and P in planter soils; (2) to determine the leaching of N and P in planter soils; and (3) to investigate the uptake of N and P by the planter greenery or vegetation. The planters were subjected to different intensities of cultivation including the type and frequency of fertilizer application. Although factors that inhibit nitrification, such as low pH, Al toxicity and low C:N ratio were not found in the planters, ammonification nonetheless predominated over nitrification. N and P mineralization proceeded favourably in the soils and was likely to be elevated by the presence of fertilizers. Immobilization of N and P was present but very site-specific. A net loss of N and P during the 56-day incubation period was detected for both Wo Che and Kwun Tong but not for Central. The implication of these findings on quality management of planter greenery in the urban environment is discussed.