ABSTRACT Soils with low potassium (K) availability require corrective fertilization for grain crops. The recommended rate to increase K availability up to the critical level depends on the soil K buffering capacity (KBC). This study aimed to quantify the KBC and recalculate the rates necessary to reach the K critical level in 23 soils from Southern Brazil. Soil samples were incubated with six K rates, that were thus grouped according to CECpH7.0: below 7.5 cmolc dm-3 (0, 30, 60, 90, […]

The use of potassium (K) rock powder can be an alternative for K supply of crops. Thus, to reduce K fertilizer imports from abroad, possibilities of extracting this nutrient from Brazilian rocks are being studied. The objective was to evaluate the effect of phonolite rock powder (F2) as K source (Ekosil®) on the air-dried fruit yield, nutrition and macronutrient export of Arabica coffee. The experiment was carried out on a dystroferric Red Latosol (Typic Haplorthox), in Piraju, São Paulo State, […]

In a system in which fertilization is recommended, diagnosis of soil K availability and the establishment of critical levels are made difficult by the possibility of a contribution of non-exchangeable forms of K for plant nutrition. Due to its magnitude, this contribution is well diagnosed in long term experiments and in those which compare fertilization systems with positive and negative balances in terms of replacement of the K extracted by plants. The objective of this study was to evaluate K […]

Soil tillage systems can greatly influence potassium and root distribution in the soil and, as a result, affect corn growth and development. To improve the understanding of these interrelationships, a soil was analyzed after 18 years of cultivation under different management systems. A detailed soil sampling was carried out in a clayey Red Argisol (Udult) profile in the beginning of the grain filling stage of corn in the 2006/07 growing season. The experimental design consisted of a completely randomized scheme […]

In the humid tropics the buildup and maintenance of soil fertility are major challenges in terms of sustainability of agroecosystems. The objective of this study was to evaluate an alley cropping system with pigeon pea (Cajanus cajan) on an Alfisol, with annual application of lime and potassium, with special concern regarding the viability of this system as an alternative to slash and burn practiced in tropical agriculture. Pigeon pea and maize (Zea mays) were planted in the experiment with the […]

Potassium uptake by plants is generally higher than the initial amount of exchangeable potassium, indicating that non-exchangeable potassium forms participate in supplying plants with this nutrient. The objective of this study was to evaluate the potassium depletion by successive cultivations in a sandy-textured soil, with and without potassium fertilization in the past. The greenhouse experiment was carried out at the Universidade Federal de Santa Maria, in southern Brazil. Samples (0-0.10 m) of a Typic Hapludalf, without and with previous potassium […]

The critical potassium level for fertilizer recommendation for soils in the State of Rio Grande do Sul (RS) and Santa Catarina (SC) with CEC from 5.1 to 15 cmolc dm-3 is 60 mg dm-3. However, until 2002 concentrations of 80 mg dm-3 had been used. Two experiments were carried out on an experimental area of the Department of Soil Science of the Federal University of Santa Maria (RS-Brazil) on a Sandy Typic Hapludalf under no-tillage. The objective of the study was to evaluate critical potassium levels […]

Nitrogen and potassium applications affected the nutrient concentration and accumulation of sweet pepper, cultivar Mayata, grown in a protected environment. An experiment was conducted in a protected environment in Eutrostox, during 34 weeks from November, 1996 to August, 1997, with the following treatments: control and combination of three rates of N (13.3; 26.6 and 39.9 g m-2) and three rates of K (5.5; 11.0 and 16.6 g m-2). All plants were watered by trickle irrigation and the urea and KCl […]