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This study was undertaken to study the impact of adding <75 μm elemental sulfur (ES) on P availability from a range of <250 μm ground rock phosphates (RP) namely; Minjingu (Mi) from Tanzania, Khouribga from Morocco (Mo) and Duchess (D) from Australia. Italian ryegrass (Lolium multiflorum, Thumpa tetraploid) grown in a glasshouse was used as the test crop and tops were harvested 5 times over 27 weeks. Co-granulating RP and 10.7% ES yielded 30–70% more ryegrass tops than RP alone, with the greatest effect with Mi. Fertilizer P recovery in the tops from the RP was 5.2% with D and 6.5% and 7.8% from Mi and Mo, respectively. ES addition increased this by 51% from Mo, 98% from D and 194% from Mi. Co-granulation of RP with ES has been shown to be an effective means of releasing plant available P to crops from RP with minimal fertilizer processing. [ABSTRACT FROM AUTHOR]

Nutrient accumulation characteristics and mineral content of plants depend on several factors such as crop and site characteristics, environmental conditions, and soil nutrient levels. Nutrient interactions are rather complex and may have an important role in this context. It is evident that phosphorus (P)–potassium (K) interaction is a part of cation–anion balance in plants. Although several authors demostrated the positive P-K interaction in plants, results are still inadequate. Studies on P-K interaction and adequate P/K ratios are needed to improve nutrient efficiency. Pot experiments were carried out under greenhouse conditions with perennial ryegrass (Lolium perenne L.) grown in three soils different in texture, soil organic matter (OM), pH, and available nutrient levels: an Eutric cambisol, a Calcaric fluvisol, and a Haplic phaeosem. Soil samples were taken from selected plots of National Long-Term Fertilization Trials (NLFT) after 30 years of fertilization. Besides the unfertilized control, increasing rates of P were applied in four replicates at four levels of P supply resulting from long-term P fertilization. Dry-matter (DM) production, P and K accumulation characteristics, nutrient concentrations, and K/P ratios of perennial ryegrass were studied for 4 months by taking four cuts. From the results, it was evident that both P and K accumulation of plants were closely related to DM accumulation. Phosphorus accumulation characteristics and amounts of P taken up by plants responded both to the level of long-term P supply and to rates of freshly applied P. Better levels of P supply had a beneficial influence on K uptake and K concentrations in plants. Phosphorus concentrations ranged between 0.20% and 0.53% P, whereas concentrations of K were between 1.63% and 5.64%. As the interaction between P and K may influence that of other nutrients, further research is needed to identify these relationships. [ABSTRACT FROM PUBLISHER]

The effects of nitrogen (N), phosphorus (P), and zinc (Zn) fertilization on the yield of ryegrass was studied in a greenhouse experiment. The treatment combination was set according to the Box-Wilson method. By performing multiple regression analysis, the yield was described as a function of fertilizer doses by a polynomial of the second degree. The R2 value of the regression was 0.863. Based on the regression equation, we calculated the optimal fertilizer doses and evaluated the effects of fertilizers by means of three-dimensional graphs. According to the graphs, it can be stated that the yield-increasing effect of N is dominant, but P and Zn doses also influenced yield. The optimum concentrations of the doses were N, 120; P2O5, 89; and Zn, 2.8 mg kg-1. Optimal dry matter (12-14 g pot-1) can be produced with a large range of Zn and P concentrations and a relatively large N range. At doses more than the optimal dose for each element, a slight depression can be observed. [ABSTRACT FROM AUTHOR]