Use Of Potassium Fertilizer Research Articles

DOSES DE FÓSFORO, POTÁSSIO E ESPAÇAMENTOS ENTRE LINHAS NA PRODUÇÃO DE SEMENTES E FITOMASSA DE GUANDU EM SEMEADURA TARDIA

O presente trabalho teve por objetivo avaliar o efeito de cinco doses de fósforo e quatro doses de potássio, em dois espaçamentos entre linhas, sobre a produção de sementes e fitomassa de guandu de ciclo curto. O trabalho foi desenvolvido em Selvíria, Estado do Mato Grosso do Sul, com semeadura em janeiro de 2005. Para a determinar o efeito dos tratamentos foi utilizado o delineamento inteiramente casualizado, em fatorial 2 x 5 x 4, com quatro repetições, sendo os tratamentos 30 e 50 cm entre linhas, 0, 40, 80, 120 e 160 kg ha-1 de P2O5 e 0, 30, 60 e 90 kg ha-1 de K2O. O espaçamento de 30 cm entre linhas proporcionou maior produção de sementes e o espaçamento de 50 cm maior altura de plantas e fitomassa. As adubações com fósforo e potássio foram positivas a todas as variáveis estudadas, sendo em geral as doses em torno de 120 kg ha-1 de P2O5 e 60 kg ha-1 de K2O as doses máximas de incremento de produção.

Long-term use of potassium fertilizer for vegetable crops in the upcountry intermediate zone

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Superphosphate and stocking rate effects on a native pasture oversown with Stylosanthes humilis in central coastal Queensland. 4. Phosphate and potassium sufficiency

Soil fertility was studied over the last 5 years of an 11 -year period in which a native pasture (Heteropogon contortus dominant) oversown with Stylosanthes humilis (TS) was fertilized annually with either 125 or 250 kg ha-1 superphosphate. A severe deficiency of potassium was found to have developed since the improved pasture was sown, and correction of the deficiency increased legume yield 2- to 3-fold and increased beef production by 24%.Pastures fertilized annually with 250 kg ha-1 of superphosphate gave no dry matter response to additional dressings of phosphorus, but those fertilized with 125 kg ha-1 annually responded slightly even after ten applications, indicating that this rate of superphosphate was close to the optimum. Three annual applications of 31 kg K ha-1 increased exchangeable soil potassium significantly and results indicate that a slightly lower rate would satisfy pasture requirements when combined with 125 kg ha-1 superphosphate. The practical implications of potassium fertilizer use are discussed in relation to the large increase in beef production possible and the need for potassium to ensure long-term maintenance of legume production. The decision to correct the deficiency would depend on local conditions and current conditions of beef production prices. Results are considered in relation to diagnosis of phosphorus and potassium deficiencies in TS in the field. For TS sampled at early flowering in March, it is concluded that fertilizer responses may be expected if phosphorus in whole plant tops is below 0.14%, or if potassium is below 0.4%, while responses are unlikely when these values are 0.17 and 0.7%, respectively. Satisfactory diagnosis would also have resulted from adoption of soil standards of 20 ppm P (extracted by 0.01 N H2SO4) or 0.20 m.equiv K 100 g-1.

Response of mown pasture to potassium fertilizer in south-eastern South Australia

Trials lasting three years were conducted at 27 sites in the south-east of South Australia to examine the responses of mown subterranean clover-ryegrass pastures to repeated annual applications of potassium chloride. At 20 sites, yield of dry matter (DM) was increased by potassium in one or more harvests. Responses were measured in 9 out of 55 winter harvests and 42 out of 86 spring harvests; mean responses to 100 kg ha-1 KCl (-Y100) at responsive sites were 380 and 560 kg DM ha-1 in winter and spring respectively. When potassium dressing increased yield, the proportion of clover in the sward was either maintained or increased. The herbage concentration of potassium was usually increased, and its magnesium concentration sometimes depressed, by potassium application. Although the K:Mg ratio was thereby increased, especially during winter, it rarely reached 15, the value considered necessary to induce grass tetany in cattle. Multivariate regression analysis showed that the exchangeable potassium concentration (Kex) of the top 10 cm of soil, the depth of soil overlying clay or limestone, and the sand content of the topsoil were factors affecting yield response. The best regression equations, however, explained less than half of the response variations. In practice, Kex alone would have usefully diagnosed potassium responsive sites. Responses occurred often when Kexwas less than 0.2 me 100 g-1 and rarely when it was greater. The use of potassium fertilizer is likely to be worthwhile to establish new pasture, to maintain the clover content of old pasture, and to increase the yield and quality of hay, where soils have less than 0.20 me 100 g-1 Kex. Such soils are most commonly sands more than 30 cm deep.

Effects of potassium fertilizers, age of ewe, and small magnesium supplementation on blood magnesium and calcium levels of lactating ewes

1. An experiment is described which investigated the effects of potassium fertilizer, age of ewe, and a small magnesium supplement, on the plasma magnesium and calcium levels of ewes shortly after lambing.2. Three potassium treatments (0, 1, and 2 cwt. muriate of potash/acre) were used, each being replicated six times, which gave a total of eighteen plots. Each plot was grazed by two old and two young ewes. One ewe of each age in every plot was given supplementary magnesium in the form of two magnesium heavy pellets, which released a total of 150 mg. Mg/day.3. 22% of the ewes had plasma magnesium values below 1·0 mg. Mg/100 ml. on at least one sampling occasion during the experimental period. There was only one clinical case of tetany.4. Neither potassium fertilizer use, nor magnesium supplementation influenced plasma magnesium and calcium levels of the ewes. Old ewes had greater temporary falls in plasma magnesium values and had consistently lower plasma calcium values.5. Attention is drawn to the large individual variation between animals and the consequent need for providing adequate statistical analysis of experiments of this type.

FACTORS AFFECTING THE SUCROSE CONTENT OF SUGARCANE: FERTILIZERS

The results of over 150 field experiments with sugarcane conducted by the Agricultural Experiment Station of the University of Puerto Rico covering a wide range of varieties and soils of Puerto Rico revealed the following: 1. Nitrogen produced an increase in sucrose content with increased cane yields. When the percentage increase in cane tonnage is plotted against the percentage increase in sucrose percent cane, a highly significant regression is obtained. The equation obtained reveals that a significant increase in sucrose concentration occurs only after increases in yields are over 27 percent. 2. Different nitrogen sources, namely, ammonium nitrate, ammonium sulfate, and Uramon, produced no significant differences in influence on sucrose concentrations. 3. The application of phosphorus had no significant effect on the sucrose content of sugarcane. Cane tonnage responses were also slight. 4. The use of potassium fertilizers did not significantly influence the sucrose content of sugarcane. Where there was an increase in yield, there was generally an increase in sucrose content. Percentage increases in yield of cane, however, were very low, the majority being less than 10 percent. The soils seem to contain sufficient potassium for good sucrose concentrations, and the use of potash as fertilizer does not usually produce any significant increases in sucrose. 5. The minor-element fertilizers produced no significant increases in sucrose content. The use of copper, magnesium, zinc, boron, manganese, calcium, sodium, iron, and sulfur produced no appreciable increases in yield. The majority of percentage yield increases were less than 7, while percentage decreases or increases in sucrose content varied from —3 to +7.