Rita Kremper

Long-Term Effect of High Phosphorus Doses on Zinc Status of Maize on a Non-Calcareous Loamy Soil

The long-term effect of 87.3 kg/ha P on the yield elements and nutrient content of maize was studied at the Na tional Long-Term Fertilization Experiment of the Karcag Research Institute in Hungary. The soil of the experiment site is non-calcareous Luvic Phaeosem, and its soluble phosphorus (P) and zinc (Zn) content in 0–20 cm soil layer are: ammonium lactate P: 141.1 mg/kg and diethylene triamine pentaacetic acid (DTPA) Zn: 0.85 mg/kg, respectively. The effect of foliar Zn fertilization was studied at three levels of nitrogen (150, 200 and 250 kg/ha) and under 87.3 kg/ha P and 82.6 kg/ha K application in four replications. The applied Zn amount was 700 g/ha. We measured the grain yield and the thousand-kernel weight. Leaf and grain samples were analyzed for phosphorus, zinc, potassium, calcium, magnesium and manganese content. Foliar Zn application did not increase the yield significantly, but it enhanced the thousand-kernel weight. The element content did not change significantly – neither in leaves nor in kernels. Under the examined habitat circumstances even the long-term application of 87.3 kg/ha P dosage did not cause Zn deficiency to such an extent which would lead to significant yield depression of maize.

Determination of Optimal Nitrogen, Phosphorus, and Zinc Doses in a Multifactoral Pot Experiment

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.

Relationship between the 0.01 M CaCl 2 - and AL-soluble soil phosphorus contents

The traditional Hungarian method for determining soil phosphorus (P) status is ammonium-lactate acetic acid (AL) extraction. AL is an acidic solution (buffered at pH 3.75), which is also able to dissolve P reserves, so there is a need for extraction methods that also characterize the mobile P pool. 0.01 M CaCl₂-P is considered to directly describe available P forms, because the dilute salt solution has more or less the same ionic strength as the average salt concentration in many soil solutions. The amount of AL-P may be two orders of magnitude greater than that of CaCl₂-P. Previous studies suggested that the relationship between AL-P and CaCl₂-P was influenced by soil parameters. Regression analysis between AL-P and CaCl₂-P showed medium or strong correlations when using soils with homogeneous soil properties, while there was a weak correlation between them for soils with heterogeneous properties. The objective of this study was to increase the accuracy of the conversion between AL-P and CaCl₂-P, by constructing universal equations that also take soil properties into consideration. The AL-P and CaCl₂-P contents were measured in arable soils (n=622) originating from the Hungarian Soil Information and Monitoring System (SIMS). These soils covered a wide range of soil properties. A weak correlation was found between AL-P and CaCl₂-P in SIMS soils. The amounts and ratio of AL-P and CaCl₂-P depended on soil properties such as CaCO₃ content and texture. The ratio of AL-P to CaCl₂-P changed from 37 in noncalcareous soils to 141 on highly calcareous soils. CaCl₂-P decreased as a function of KA (plasticity index according to Arany), which is related to the clay content, while the highest AL-P content was found on loam soils, probably due to the fact that a high proportion of them were calcareous. The relationships between AL-P, CaCl₂-P and soil properties in the SIMS dataset were evaluated using multiple linear regression analysis. In order to select the best model the Akaike Information Criterion (AIC) was used to compare different models. The soil factors included in the models were pHKCl, humus and CaCO₃ content to describe AL-P, and KA, CaCO₃ content and pHKCₗ to describe CaCl₂-P. AL-P was directly proportional to pHKCₗ, humus and CaCO₃ content, while CaCl₂-P was inversely proportional to KA, CaCO₃ content and pHKCₗ. The explanatory power of the models increased when soil properties were included. The percentage of the explained variance in the AL-P and CaCl₂-P regression models was 56 and 51%, so the accuracy of the conversion between the two extraction methods was still not satisfactory and it does not seem to be possible to prepare a universally applicable equation. Further research is needed to obtain different regression equations for soils with different soil properties, and CaCl₂-P should also be calibrated in long-term P fertilization trials.

Assessment of Environmentally Harmful Nitrogen Surplus by 0.01 M Calcium Chloride Soil Extractant in Long-Term Experiments

Calcium chloride–extractable (1:10 soil/solution ratio, w/v) nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), organic nitrogen (EON), and Ntotal fractions were measured in two long-term experiments. Both experiments are located in the Great Hungarian Plain. The first experiment was established on a Luvic Phaeozem soil and the second experiment was on a Calcic Chernozem soil. Researchers investigated the effects of long-term fertilization and irrigation on the amounts of nitrogen (N) fractions. Nitrogen rates caused significant increase in NO3-N and Ntotal fractions. These fractions were in close correlation (r = 0.87; r = 0.88) with nitrogen balance. The nitrate content of the 200-cm-deep soil layer of soils under different nitrogen- and water-supply conditions were also studied. As an effect of N overfertilization, the maximum nitrate accumulation on nonirrigated plots occurred in the 200-cm depth, whereas on irrigated plots a nitrate accumulation layer could not be observed in the 200-cm-deep soil layer.