K2O Application Research Articles

Productivity of soybean crop after fertilization with normal and polymer-coated potassium sources

The adoption of different fertilizer application methods should consider the operational, agronomic and economic aspects. The objective of this work was to study the fertilization response with potassium in the soybean crop at different times of application and different potassium sources in an Eutroferric Red Latosol. The experiment was carried out in the municipality of Formosa do Oeste-PR. The design was in a randomized block in a factorial scheme (2 × 5) +1, with 2 potassium sources: normal KCl (KCl) and polymer-coated KCl (KCl-polymer), the KCl doses were adjusted to 40 kg ha -1 of K2O, the second factor refers to the splitting of K2O dose in five application times: T1, application of K2O was nine days before sowing, T2 application split up being ½ of the dose nine days before sowing + ½ of the dose of K2O at sowing, T3 application of the total dose of K2O at sowing, T4 ½ of the dose at sowing + ½ at the V3 phenological stage of the crop, T5 application of K2O was total at the V3 stage of the crop. And an additional witness, without K2O application. KCl-polymer was more efficient for application to the haul before sowing the crop. The fertilization with KCl was better when applied at the V3 stage of the crop. Fertilization with KCl-polymer resulted in higher K content in the leaf, higher efficiency of fertilizer use reflecting in higher productivity.

Influence of varying potassium levels on yield, water productivity, profitability and resource-use efficiency in kharif mungbean (Vigna radiata) under semi-arid conditions of Afghanistan

The application of K2O @ 80 kg/ha could be used as blanket recommendation for obtaining higher productivity, profitability as well as higher resource-use efficiency in kharif mungbean. As a site-specific precision recommendation, the economic optimum K2O dose for kharif mungbean variety NM-94 was worked-out about 76.9 kg K2O/ha which has great promises in saving the potassium fertilizer dose besides enhancing kharif mungbean productivity, profitability and resource-use efficiency under semi-arid conditions of Afghanistan.

Physiological Mechanism and Nutrient Management Strategies for Flood Tolerance in Rice Grown in Lowland Flood Prone Ecosystem

In flood-prone areas, rice must have flood tolerance characteristics either through genotypic selections or by nutrient application management strategies. The current study was conducted at ICAR Research Complex for Eastern Region, Patna during the wet season to investigate the effect of post-flood nutrient application methods on submerged rice survival and productivity. Our study showed that the 3-d submergence duration had no effect on the survival (100%) of 21-day-old seedlings but survival percentage decreased to 97 and 65% at 7-d and 11-d submergence, respectively. Total chlorophyll, total soluble sugar, and starch concentrations also exhibited a similar pattern of decline. The activity of anti-oxidative defense enzymes (CAT, POX, SOD, and APX), recorded just after de-submergence was found to be 1.5-10-foldhigher than before submergence, increasing with the increase in the severity of stress. Additional post-flood application of K2O and N at 5-6 days after de-submergence led to the improvement in photosynthetic rate, yield attributes, and grain yield. An additional 10 kg each of N and K2O produced maximum 1000-grain weight and higher grain yield and harvest index. After submergence, the meta-analysis exhibited a significant reduction in total chlorophyll concentration due to increasing submergence duration, whereas the significantly higher activity of antioxidants was recorded irrespective of submergence duration. In association with the better anti-oxidative defense mechanism of Sub1 varieties, the additional doses of N and K2O at 5-d after de-submergence significantly enhanced the survival, post-flood recovery, and the rate of photosynthesis after de-submergence. These nutrient management options can provide an opportunity to explore the productivity potential of the SUB1-introgressed variety under natural flash-flood conditions, helping to cope with the existing problems in flood-prone areas. The findings of the study suggest that a proper time and method of N application with basal P can significantly contribute to higher rice yield in flash-flood prone areas.

The split application of potassium influence the production, nutrients extraction, and quality of sweet potatoes

The current study aimed to evaluate the effect of split application of potassium (K) fertilizer on the production and quality of sweet potatoes. Ten treatments were evaluated in factorial design (3 × 3 + 1): three doses of potassium (60, 90, and 120 kg K2O ha−1); three application types (100% applied at planting; 50% applied at planting and 50% was given as topdressing; 25% applied at planting and 75% was given as topdressing) and one control (without the application of K2O either at planting or topdressing). The experiment used a randomized complete block design and four repetitions. The following parameters were studied: root number; root fresh matter per plant; total dry matter; yield; total macronutrient extraction; sugar content of starch; and commercial starch. The production characteristics of the roots presented a significant interaction between the factors doses of potassium and application types (parcelaments). Finally, better results were obtained when potassium was applied 50% at planting and 50% as topdressing.

Potassium Dynamics in Inceptisols as Influenced by Graded Levels of Potash for Banana: I. Potassium Fractions

ABSTRACTKnowledge of forms of potassium (K) in soil is of great importance for formulating sound fertilizer recommendation to banana. Field experiments were conducted to study the effect of graded levels of potash application on forms of potassium at juvenile, grand growth, shooting, and harvest stages of banana on Vertic Haplustept soil. The negative balance of soil-available K was observed in the treatments of 0, 100, and 200 g K2O plant−1. However, at 300-g K2O plant−1 level, the balance was a mere –11 kg ha−1, and positive balance was observed in the treatments of 400 and 500 g K2O plant−1. Significant positive correlation among different forms of K indicated the interdependency and dynamic equilibrium between K forms. Application of K2O above the level of 300 g plant−1 for banana resulted in the build-up of potassium fractions in soil.

Doses e épocas de aplicação de potássio no desempenho agronômico do milho no cerrado piauiense

Since the ‘Cerrado’ area of Piaui State, Brazil is a relatively new agricultural frontier, there is lack of information regarding the handling of potassium fertilization, since no information about the better fertilization techniques for this area was provided by the federal research corporations. Thus, the aim of this study was to evaluate the effect of dose and time of application of K2O in corn grown in a ‘Cerrado’ area at the Paui state. The experiment was conducted in a yellow dystrophic oxisol with a completely randomized block design, with four repetitions in a (4x4)+1 factorial. The treatments consisted of combinations of four potassium levels: 30, 60, 90 and 120 kg ,K2O ha-1 + additional control (zero kg ha-1) applied in four seasons : 100% at sowing; 100% at 30 days after sowing (DAS); 50% at sowing and 50% 30 DAS; 50% 20 DAS and 50% at 40 DAS. Only the height, stem diameter and agronomic efficiency of the K use were influenced by the K+ time of application, especially with the application of 50% at sowing and 50% at 30 DAS. Except for the relative chlorophyll content and ear length, all other variables were influenced by K2O doses. The application of K2O resulted in greater increases of other evaluatedvariables, mainly for the yield obtained when the dose of (53 kg K2O ha-1 was used,.

Chemical quality of a Yellow Latosol under pasture submitted to levels and frequency of fertilization and liming

In the period 1996 to 2000, at Embrapa Rondônia, Porto Velho was evaluated the effects of levels and frequency of fertilization and levels of liming on the chemical attributes of a dystrophic Yellow Latosol, clay texture, under pasture of Brachiaria brizantha cv. Marandu in the process of degradation. We adopted the experiment in design of randomized blocks with three replicates, in a factorial arrangement 2 x 2 x 2 x 2 to the levels of liming (aiming at saturation V-20 and 40% - dolomitic lime with 70% PRNT), nitrogen fertilization (50 and 100 kg ha-1 of urea-N), phosphate (50 and 100 kg ha-1 P2O5 - triple superphosphate) and potassium (30 and 60 kg ha-1 of K2O, potassium chloride); and 3 x 2 x 2 x 2 for fertilization frequencies (annual, biennial and triennial), being reapplied the same doses of fertilizers, there was no replacement of lime. In the implementation of the experiment the lime and fertilizers were coverage distributed and incorporated into the soil by light disking, reapplication in the fertilizers were distributed in the same way but not incorporated. After four years, were collected representative samples of soil, at depths of 0 to 15 cm and 15 to 30 cm, which were analyzed chemically. The results obtained for each soil layer were subjected to analysis of variance and means were compared by Tukey test. Independent levels of fertilizer, when liming from 20 to 40% of V, decreased potential acidity, active acidity and Al+3, neutralizes its toxicity; happening the inverse in the pH in H2O, the sum of exchangeable bases and V, mainly in the depth 0-15 cm soil. In both depths, P fertilization had a direct effect on the levels of total P in soil; while the application of K2O did not alter the availability of this nutrient, nor the additional N was able to increase the content of soil organic matter. Only the total P was influenced by the frequency of fertilization, lower concentrations were obtained with the three year reapplication, and higher in the biennial. The application of lime in order to increase the 40% V, increases the pH in H2O, the exchangeable bases and V, reduces the ion Al+3 and neutralizes its toxicity; most notably in the topsoil (0-15 cm). The minimum levels of fertilization in kg ha-1 should be: 100, 50 and 60 of N, P2O5 and K2O, respectively. Lime and fertilizer can be distributed to haul without soil incorporation, when you want to fix and fertilize the top layer of grass (0-15 cm depth).

Agronomic Characteristics Related to Grain Yield and Nutrient Use Efficiency for Wheat Production in China.

In order to make clear the recent status and trend of wheat (Triticum aestivum L.) production in China, datasets from multiple field experiments and published literature were collected to study the agronomic characteristics related to grain yield, fertilizer application and nutrient use efficiency from the year 2000 to 2011. The results showed that the mean grain yield of wheat in 2000–2011 was 5950 kg/ha, while the N, P2O5 and K2O application rates were 172, 102 and 91 kg/ha on average, respectively. The decrease in N and P2O5 and increase in K2O balanced the nutrient supply and was the main reason for yield increase. The partial factor productivity (PFP, kg grain yield produced per unit of N, P2O5 or K2O applied) values of N (PFP-N), P (PFP-P) and K (PFP-K) were in the ranges of 29.5~39.6, 43.4~74.9 and 44.1~76.5 kg/kg, respectively. While PFP-N showed no significant changes from 2000 to 2010, both PFP-P and PFP-K showed an increased trend over this period. The mean agronomic efficiency (AE, kg grain yield increased per unit of N, P2O5 or K2O applied) values of N (AEN), P (AEP) and K (AEK) were 9.4, 10.2 and 6.5 kg/kg, respectively. The AE values demonstrated marked inter-annual fluctuations, with the amplitude of fluctuation for AEN greater than those for AEP and AEK. The mean fertilizer recovery efficiency (RE, the fraction of nutrient uptake in aboveground plant dry matter to the nutrient of fertilizer application) values of N, P and K in the aboveground biomass were 33.1%, 24.3% and 28.4%, respectively. It was also revealed that different wheat ecological regions differ greatly in wheat productivity, fertilizer application and nutrient use efficiency. In summary, it was suggested that best nutrient management practices, i.e. fertilizer recommendation applied based on soil testing or yield response, with strategies to match the nutrient input with realistic yield and demand, or provided with the 4R’s nutrient management (right time, right rate, right site and right fertilizer) should be adopted widely to improve the yield production and nutrient use efficiency.

Doses e épocas de aplicação de potássio na cultura da soja em sucessão a plantas de cobertura

Potassium (K) is the second nutrient that is required in larger amounts by soybean crop. With the use of high doses of that nutrient and increase of no-tillage areas in last years, some changes occurred in ways of this nutrient application, as well as the introduction of cover crops in the system for straw formation. Due those facts, the aim with this work was to study doses and times of potassium application for soybean sowed as succession for cover crops in no-tillage system, in a clayey Distrofic Red Latosol, in cerrado region. The experimental design was a randomized block with treatments arranged in 3x3x5 factorial scheme, with the following factors, cover crops: Pearl millet (Pennisetum glaucum) and Proso millet (Panicum miliaceum) and a control (fallow area), rates of K2O (0, 50 e 100 kg ha-1) and K2O application forms (100% in the cover crops; 100% at sowing of soybean; 100% in topdressing in soybean; 50% at sowing cover crops + 50% at soybean sowing; 50% at soybean sowing + 50% in topdressing in the soybean) with four replicates. The Pennisetum glaucum as soybean predecessor crop yields higher dry matter content than the Panicum miliaceum in a short period of time. In clay soil with high content of potassium there was no response to the applied potassium levels. Full doses of potassium maintenance fertilization can be applied in the predecessor cover crop, at sowing or topdressing in soybean crop.

Soil chemical properties as affected by plant derived ash to replace potassium fertilizer and its conversion value

Potassium chloride (KCl) presently used as main source of K, tends to become more expensive, therefore, there is a need for a breakthrough in finding alternative materials to replace KCl. The aim of this paper is to present recent research on the use of plant derived ash to replace KCl fertilizer, especially in relation with soil chemical characteristics and its conversion value. Plant derived ash coming from palm sugar processing unit which use farm waste as main fuel was used in this experiment. Treatments investigated were no K2O application (control), applied with K2O in forms of both KCl and plant derived ash in dosages of 100, 200, 300, 400, 500 and 600 mg kg-1 air dry soil. The mixture of soil with those treatments were then incubated for one year. After incubation period, the soil in pots were divided into two parts, first part was added with 2g urea, while other part was added with 2 g SP 36. Both parts were incubated for two months. Results of this experiment showed that plant derived ash can be used to replaced KCl. To obtain similar soil K content, the amount of K2O in form of plant derived ash needed to be added or its conversion value is 1.44 times the amount of K2O in form of KCl. Use of plant derived ash also increased the content of soil Ca, available P, ratio of Ca/Mg and pH. Plant derived ash did not caused nitrogen loss. Key words: Potassium, fertilizer, plant derived ash, pH, soil.

FONTES E DOSES DE NPK EM MILHO IRRIGADO SOB PLANTIO DIRETO

Coated fertilizers can provide lower losses and higher soil nutrients availability, which can be absorbed by plants, when we consider their gradual release. The objective of this study was to evaluate the effect of doses and sources of N, P, and K on maize grain components and yield, under no-till system, in the Brazilian savannah. The experimental design was randomized blocks, with 4 top-dressed doses (0 kg ha-1, 40 kg ha-1, 80 kg ha-1, and 120 kg ha-1) and 2 sources (urea and coated urea), for N; 4 doses (0 kg ha-1, 50 kg ha-1, 100 kg ha-1, and 150 kg ha-1) and 2 sources (triple superphosphate and coated triple superphosphate), for P; and 4 doses (0 kg ha-1, 40 kg ha-1, 80 kg ha-1, and 120 kg ha-1) and 2 sources (potassium chloride and coated potassium chloride), for K, with 4 replications. The fertilizers coated with polymers (urea, triple superphosphate, and potassium chloride) were not efficient under the soil and climate conditions studied, because they provided results similar to the same conventional fertilizers, for the N, P, and K foliar contents, and irrigated maize grain components and yield. The increment of N doses increased linearly the N leaf content, number of ears per hectare and maize grains yield. The application of K2O and P2O5 doses did not influence grain yield.

Spectral characterization and prediction of nutrient content in winter leaves of litchi during flower bud differentiation in southern China

Nutrient availability can affect the cracking rate of the litchi fruit tree, and the nutrient content of the canopy can be used to monitor availability and fertilizer needs of the litchi orchard. In this study, we analyzed the correlation between calcium (Ca), magnesium (Mg) and potassium (K) in canopy leaves and four indices of in situ spectral data of litchi canopy. These were reflectance (R), reciprocal-logarithm-transformed reflectance (log(1/R)), the first-order derivative of reflectance (dR) and the first-order derivative of reciprocal-logarithm-transformed reflectance (dlog(1/R)). The results showed that the spectra of the litchi canopy have common spectral characteristics. The correlation between the selected nutrients of the litchi canopy and R or log(1/R) was weak, that between the nutrients and dR was significant and with dlog(1/R) it was the most significant. The 1262 nm wavelength for dR and 1018 nm one for dlog(1/R) had the most significant correlation with Ca. The 1293 nm wavelength for dR and 1601 nm one for dlog(1/R) had the most significant correlation with Mg. The 1686 nm wavelength for dR and 1337 nm one for dlog(1/R) had the most significant correlation with K. Therefore, those wavelengths were chosen to create the regression equations for prediction. The linear regression equations performed the best when predicting canopy nutrient content of litchi for Ca at 1018 nm, Mg at 1601 nm and K at 1337 nm. Further, the formulated application of K2O played an important role in reducing the amount of K2O applied (50.6 g/plant on average) and in increasing the yield of the litchi tree by 4.4 kg/plant on average. These results are relevant for implementing a precision agriculture approach for litchi production and for environmental protection in South China or in other litchi production areas of the world. Other nutrients that affect litchi growth need to be studied in the future.

Utilização de coberturas de solo no cultivo de alface ‘Babá de Verão’ em Cassilândia (MS)

The research had as objective to analyze the effects of water depths, potassium levels and the interaction between these factors which are related with vegetative growth and the parameters related with nutritional situation of the precocious dwarfish cashew tree (Anacardium occidentale L.) variety BRS189. The statistical design was of completely randomized blocks in split-plots, with four primary treatments (25, 50, 100 and 150% ETc), four levels of potassium (0, 30, 60 and 120 g of K2O plant1 year-1) and four blocks. The crop was installed at 7.0 x 7.0 m spacing, irrigated by a microsprinkle irrigation system. The height and diameter characteristics of stem plants were analyzed below and above the graft, besides the nutritional situation. The results allowed the following conclusions: the factor of potassium production had a positive influence in the plant height and medium diameter of the stem below the graft, while the factor water didn’t have influence in any of the analyzed characteristics. Application of K2O up to 52 g.plant-1.year-1 is not recommended, then providing a decreasing in the potassium concentration (%) in the precocious cashew tree-dwarf’s leaves BRS–189.

Effect of Potassium Application Rates on Nitrogen Absorption and Utilization of Different Types of Rice

Potassium, nitrogen and their interaction play important roles in plant growth, development and yield of rice. Appropriate potassium can stimulate nitrogen accumulation and translocation in rice. In order to identify plant nitrogen absorption, distribution and utilization characteristics of rice under potassium supply, a field experiment was conducted with four potassium rates (0, 90, 180, 270 kg ha-1 K2O) using conventional japonica cultivars (Wuyunjing 7 and Wuxiangjing 14) and hybrid japonica cultivars (86 you 8, Siyou 422) from 2004 to 2005 on Experimental Farm of Nanjing Agricultural University, Jiangsu province, China. Potassium application increased rice yield (4.56?14.77%) and nitrogen accumulation during growth stages, with the maximum from elongation stage to heading stage, but nitrogen uptake ratio decreased. Potassium application enhanced nitrogen transport amount and percentage after anthesis, as well as nitrogen accumulation in different rice organs, nitrogen distribution percentage in leaves and panicles, whereas declined nitrogen distribution percentage in culm and sheath. Nitrogen absorption from fertilizer, basic nitrogen recovery efficiency before elongation stage, nitrogen recovery efficiency during the whole growing stage, and nitrogen harvest index were raised significantly, but plant nitrogen productivity was opposite. Grain yield, nitrogen accumula- tion, nitrogen translocation amount and percentage after anthesis, and nitrogen distribution in different rice organs amounted to the maximum at K2O application rate of 180 kg ha-1, as well as nitrogen absorption from fertilizer, basic nitrogen recovery efficiency before elongation stage, nitrogen recovery efficiency during the whole growing stage. However, nitrogen absorption percentage from elongation stage to heading stage, nitrogen distribution percentage in culm and sheath, plant nitrogen productivity decreased to the minimum. The yield and nitrogen recovery efficiency of conventional japonica cultivars were higher than those of hybrid japonica cultivars.

Produtividade e qualidade de frutos de meloeiro cultivado em ambiente protegido com aplicação de dióxido de carbono e de potássio via água de irrigação

The aim of this work was to study the effect of different doses of carbon dioxide (CO2) and potassium (K2O), applied through drip irrigation, at the yield and quality of cantaloupe melon (Cucumis melo L.), hybrid Bônus II, cultivated in greenhouse. 19-day seedlings were transplanted to beds. They were spaced out 1.1 m x 0.3 m apart from each other and vertically directed up to 2.0 m of height. The treatments resulted from combinations of four K2O doses and four CO2 doses applied during the crop. K2O irrigation and application were carried out during four days. CO2 irrigation and application were carried out during two days. 45 CO2 irrigation, 33 CO2 applications and 19 K2O applications were totalized. Results showed that (a) based on a quadratic relation, the number of melon marketable fruits had a significant increase when CO2 and K2O doses were also increased; (b) there was no significant effect of CO2 on the average fruit weight. However, there was a significant quadratic effect for K2O; (c) based on a quadratic relation, when there was an increase of CO2 and K2O doses, the total and commercial melon yield also increased; (d) CO2 and K2O application through irrigation increased the water efficiency usage; (e) there was significant effect of CO2 on the total acidity, on the soluble solids content and on the flesh pH. However, there was no effect of K2O; and (f) K2O application affected significantly the melon flesh thickness and the fruits transversal and longitudinal diameters. CO2 application affected the flesh thickness and firmness.

Efeito da calagem e adubação da seringueira no estado nutricional e produção de borracha seca

Foram avaliados os efeitos da calagem e da adubação NPK no estado nutricional e na produção de borracha seca do clone RRIM 600. Utilizou-se o delineamento de blocos casualizados, com quatro repetições, em parcelas subdivididas. Nas parcelas foram testados duas testemunhas (sem adubação e sem calagem; sem adubação e com calagem), e seis tratamentos com calagem e adubação (N1P1K0, N2P2K0, N1P1K1, N2P2K1, N1P1K2 e N2P2K2). Os níveis anuais de NPK utilizados corresponderam a 40 e 80 kg ha-1 de N, 17,5 e 35,0 kg ha-1 de P2O5 e 0, 33,2 e 66,4 kg ha-1 de K2O. Nas subparcelas foram utilizados os sistemas de explotação ½S d/4 6 d/7 ET 2,5% LaPa 1/1 10/y e ½S d/6 6 d/7 ET 5,0% LaPa 1/1 10/y. Houve efeito significativo dos tratamentos sobre os teores de N, P, S, Cu e Zn nas folhas. A aplicação de N, nas duas doses, não elevou o seu teor nas folhas. O aumento nas doses de K2O na presença de N2P2 promoveu decréscimo no teor de zinco. A maior produção de borracha seca (1.778,9 kg ha-1), na média dos três anos, foi obtida no tratamento N2P2K1 + calagem nos dois sistemas de explotação.

Responses of Irish potatoes (Solanum tuberosum L.) to mineral and organic fertilizer in various agro-ecological environments in Kenya

The response of potatoes (Solanum tuberosum L.) to application of inorganic and organic fertilizer was studied in long-term field experiments between 1987 and 1994. Responses to phosphorus and nitrogen were tested at 27 sites and to potassium at 17 sites. The sites represented various agro-ecological zones in Kenya. Phosphate (triple superphosphate, TSP) and nitrogen (calcium ammonium nitrate, CAN) fertilizer were applied at 0, 25, 50 or 75 kg P2O5 ha−1 and 0, 25, 50 or 75 kg N ha−1. Potassium (muriate of potash) was tested mainly on sites with low levels of K in the soil at rates of 0 or 50 kg K2O ha−1. Farmyard manure was applied at 0 or 5 t ha−1 with or without N and/or P2O5 fertilizer.Over the study period average yields varied considerably between sites and agro-ecological zones. At 16 of the 27 sites, potatoes responded strongly to the application of P2O5 and at 9 sites to N application. A significant response to K2O application was found at three out of the 17 sites. Nutrient use efficiency ranged from 13 to 214 kg tubers per kg P2O5 and from 20 to 113 kg tubers per kg N applied. In the majority of the sites, both N and P response followed a linear function which suggests that application rates higher than 75 kg N ha−1 and/or 75 kg P2O5 ha−1 could be beneficial. Economic analysis revealed that in most cases fertilizer application was highly profitable for potatoes.The critical soil P value was about 15 ppm (mod. Olsen) for optimal potato nutrition; on soils with higher P levels generally no P response was found. The respectively critical soil K value was found to be about 0.55 meq 100 g−1 (modified Olsen). Farmyard manure at 5 t ha−1 significantly increased yields of potatoes at 9 of the 27 sites. On soils with P levels below 12 ppm, there was a positive effect on potato yields with a combination of 50 kg P2O5 ha−1 and farmyard manure, although significant differences were achieved in only one out of the 19 sites.

Efecto de cantidades y métodos de la aplicación de potasa en el rendimiento de tomate, variedad Duke

En 1988 y 89 se establecieron dos experimentos de campo en la subestación de Fortuna para evaluar cantidades y métodos de la aplicación de potasa en el rendimiento de tomate de la variedad Duke. Las aplicaciones de K2O entre 0 y 336 kg./ha. en banda (a mano) o por el sistema de riego por goteo no afectaron significativamente (P 0.05) el rendimiento medio de tomates entre tratamientos. El rendimiento medio de tomates en el experimento de 1988 fluctuó entre 46,689 kg./ha. para el tratamiento 0 K2O, 45,605 kg./ha. para 336 kg. de K2O/ha. aplicados en banda y 48,617 kg./ha. en aplicación combinada por goteo y banda. Los números correspondientes para el experimento de 1989 fueron 46,752, 47,962 y 44,060 kg./ha, respectivamente. Las producciones más altas como promedio para los experimentos de 1988 y 1989, se obtuvieron con 196 kg. de K2O/ha. en aplicación combinada de goteo y banda y 252 kg. de K2O/ha. en banda, con 48,095 y 48,010 kg./ha., respectivamente, mientras que el tratamiento con 0 K2O produjo 46,707 kg./ha. La ausencia de respuesta significativa a la aplicación de K2O parece ser el resultado de un alto contenido inherente de K disponible en el suelo San Antón (367 p/m) que prevalece en el lugar del estudio, el cual se comprobó mediante análisis de laboratorio.

Comparison of Five Fertilization Programs for Fish Ponds

Abstract Five fertilization programs were compared in sunfish ponds at Auburn, Alabama, during the 1980 growing season. Each fertilization program was replicated four times and fertilizers were applied on 12 dates. Amounts of fertilizer per application, types of fertilizer (percentages by weight), and net production of sunfish were: 45 kg/hectare of fishpond fertilizer (N-P2O5-K2O:20–20-5), 228 kg/hectare of sunfish; 20 kg/hectare of triple superphosphate (0–46-0), 298 kg/hectare; 10 kg/hectare of triple superphosphate, 226 kg/hectare; 10 kg/hectare of diammonium phosphate (18–46-0), 308 kg/hectare; and 8 kg/hectare of liquid fertilizer (13–25-0), 228 kg/hectare. None of the values for net production differed significantly (P > 0.05), even though there were considerable differences in N, P2O5, and K2O application rates among treatments. Net production of sunfish in two control ponds was only 125 kg/hectare—a value comparable to those reported for other unfertilized ponds in the Piedmont area of Alabama. C...

CHANGES IN SOIL FERTILITY UNDER INTENSIVE RICE CROPPING WITH IMPROVED VARIETIES

To monitor changes in the capacities of rice soils to supply NPK over a period of intensive cropping, fertilizer trials were conducted for 10 consecutive cropping seasons from 1968 to 1972 at three experiment stations of the Philippine Bureau of Plant Industry. Each trial included three indicator varieties, with IR8 as the common variety, throughout the 10 crops and in all locations. At all locations, the efficiency of nitrogen use was highest in the first crop and declined with successive croppings; for phosphorus, the trend was opposite. Phosphorus responses were greater with K2O application, especially in the dry seasons. We observed a marked response to potassium, especially at Bicol. The efficiency of K use increased sharply over the years, especially in the dry seasons. Split application of K gave no clear-cut advantage over basal application. Some varieties responded better than others to K, but only in soils which responded well to K. Results indicate that in areas where one crop per year is grown, with adequate N supply, responses to P and/or to K may be marginal. Responses may become marked, however, under intensive rice cultivation.