Katalin Sárdi

CORRELATION BETWEEN SOIL P AND CORN LEAF P CONTENTS IN A NETWORK OF HUNGARIAN LONG-TERM FIELD TRIALS

Corn (Zea mays L.) leaf weight, leaf P concentrations at flowering stage, 0.01 M CaCl2-, Olsen-, LE-, and AL-soluble soil P contents were determined in a network of uniformed 27-year-old Hungarian long-term field trials (the so-called National Long-term Field Trials, NLFT) with four P fertilization rates on nine locations, representing various agro-ecological and soil conditions of the country. A 4–5 fold increase in soluble P contents was found in all soil P-tests, while the absolute values of dissolved P varied greatly (CaCl2-P: 0.1–3.7; Olsen-P: 3.7–47.7; and AL-P: 12.8–182.2 mg P kg−1). On the other hand, an average twofold difference occurred among the sites in case of soil P-test methods less dependent of soil properties (CaCl2, Olsen), and a fourfold difference in methods using acid solvents, more dependent of soil reaction status and CaCO3 content. On the average of all soils and all P levels, the amount of P dissolved by the different methods increased in the sequence of CaCl2<Olsen<LE<AL (1.5<20<44<74 mg P kg−1). The different agro-ecological conditions had a greater effect on corn leaf weights at flowering stage than soil-P status. Corn leaf P concentrations, however, were affected by both the P rates and the different sites, resp. There was no significant correlation between Olsen-P values and corn leaf weights. Corn leaf weight, however, increased jointly with soil test values, up to 10–15 mg/kg Olsen-P concentration. There was a weak quadratic correlation between corn leaf P concentrations and leaf weights (r=0.35* *). Above 0.25% leaf P concentrations, leaf weights did not increase any more. On calcareous soils, P-overfertilization could result in Zn deficiency induced by P. There was a moderate, logarithmic correlation between Olsen-P and leaf P contents (r=0.62* * *). The lower limit of good P supply,—indicated by 0.26% leaf P concentration at flowering stage—was usually reached when the Olsen-P value was around 10 mg/kg. Only the CaCl2- and Olsen-methods proved to be independent of soil reaction status. A strong, linear correlation was found between these two methods (r=0.80* * *). The behavior of acid LE- and AL- solvents, however, was different in acid and calcareous soils. Correlation between Olsen- and LE-, as well as between Olsen- and AL-methods could be found separately for acid and calcareous soils. The closeness of correlation within the calcareous soil group and within the acid soil group was similar (r=0.89* * * and 0.90* * * for the calcareous, and r=0.89* * * and 0.94* * * for the acid soils group). Soil and plant P analyses data proved to be useful tools in adapting the results of long-term field trials for improved, environmentally sound fertilizer recommendations.

Changes in the soil phosphorus content of a long-term fertilization field trial studied in laboratory incubations

Abstract The importance of different soil phosphorus (P) compounds and their transformation influenced by several soil and other factors is well established. However, the dynamics of short‐term processes taking part in the long‐term changes of soil P including immobilization and mobilization is still not completely documented. Laboratory incubation experiments were carried out at 10°C and 40°C for studying the influence of incubation on the availability of residual and freshly applied P in samples of a long‐term fertilization field trial conducted on a brown forest soil (U.S. taxonomy: Orthic Eutrochrept; FAO taxonomy: Eutric Cambisol). Samples showing three levels of P resulting from 10 years of intensive P fertilization (referred as P0, P1 and P2, respectively), were collected 30 years after fertilization ceased. Available P contents of soil samples were determined using three approaches: in water (modified Murphy–Riley method), sodium bicarbonate (Olsen, pH=8.5), and ammonium lactate (AL, pH=3.7) extract. Changes in the amounts of P were determined after 2 and 60 days of incubation in four freshly applied new treatments with increasing additions of P: 0, 100, 500, and 1000 mg of P2O5 per kg of soil, representing agronomic and extreme P rates. From the results of our experiments, it was suggested that after 2 days of incubation, at 10°C, both agronomic and extreme P rates resulted in significant increases in P content in each extract. On the other hand, after 60 days, even higher values were obtained. Decreases found in water‐P values after 60 days of incubation were considerable compared to either the Olsen‐P or the AL‐P values, indicating the decline of water‐soluble P forms and further evidence of immobilization with increasing incubation time and temperature. Correlation between water‐P, Olsen‐P, and AL‐P values were significant at both temperatures.

Correlation between Soil P Test Results and P Contents of Young Spring Barley Studied in Long-Term Experiments

Interpretation of soil test results and plant analysis data are important for the further development of nutrient management in cereal production. The main objective of our pot experiments was to study the effects of increasing rates of phosphorus (P) fertilization (including agronomic and extreme P levels) and responses of young spring barley (Hordeum vulgare L.) grown in two soil types: a sandy loam (FAO taxonomy: Eutric cambisol, USA taxonomy: Orthic Eutrochrept) and a silt loam (FAO taxonomy: Stagnic luvisol, USA taxonomy: Typic Albaqualf). Ten‐year intensive fertilization resulted in three P levels (referred as P0, P1, and P2). Soil samples were taken from selected plots 30 years after stopping fertilization. Available soil P was determined in the ammonium lactate (AL P) and sodium bicarbonate (Olsen P) extract. Relationships between soil P tests, dry‐matter (DM) production, and P contents of young barley plants were evaluated. Significant correlations were found between soil P test values and both DM production and shoot P contents (R2 values ranged between 0.5047*** and 0.9751***). Correlations were closest between AL P and Olsen P values in both soils (R2 = 0.9748 and 0.9739, respectively).

Comparative Cost Analysis of Organic and Conventional Farming in Hungary

The cost–profit relations of organic and conventional farming were examined using natural and financial data of a large agricultural company in western Hungary and economic models characterizing private farms in eastern Hungary. The differences in cost structures reflect variable conditions relating to certain crops but they can be well explained by the differences in the technologies used. According to the production data, direct costs per hectare in organic farming were less in all of the four examined crops. Even cost per production unit and contribution were more favorable in three of the investigated crops. Regarding the calculation done by economic models, the costs per hectare relating to the two production methods were not significantly different. Yields in organic crop production were typically less; however, costs per unit and selling prices were greater. Differences in gross profits may be explained by different yields and selling prices. In most of the developed model variations, organic farming is more profitable; however, the extra price for organic products is not sufficient for achieving a greater profit in every year.

Interrelations in Phosphorus and Potassium Accumulation Characteristics of Plants Grown in Different Soil Types

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.

WATER-SOLUBLE P AS AFFECTED BY FRESHLY APPLIED AND RESIDUAL P AND P FRACTIONS OF SOIL

Water-soluble P content of soils is not regularly investigated in Hungary, but we need to understand its dynamics as influenced by previous and recent fertilization in order to predict dissolved P load from agricultural areas at the watershed of Lake Balaton, Hungary. Two sites were selected from a long-term fertilization trial representing characteristic soils around the lake. Soil samples from plots with different P fertilization were investigated in an incubation experiment in which fresh P was applied in a single dose or split and water-soluble P was measured. Available P, water-soluble P and modified Hedley P fractions were determined on the original samples. The soil at Keszthely has lower total P content, but higher rates of available (ammonium-lactate-soluble) P and mineralizable Hedley P fractions than the soil at Bicsérd. Because of these “light” fractions, the incubation produced temporarily high-water soluble P content even in the unfertilized soil. Initial quick fixation of freshly applied P has been higher in the soil at Bicsérd (65–75%) than at Keszthely (55–70%). Further, the soil at Bicsérd has additional capacity to fix P (approximately 1% per week) and that property was only slightly influenced by the fertilization history. However, only the soil from unfertilized plot at Keszthely has shown this ability. Soils like we have collected at Keszthely pose higher risk to pollute Lake Balaton with P than soils from Bicsérd. Regulations in order to reduce P load should be focused more on the previous soils.

Short-Term Transformation and Dynamics of Main Nutrients in Soil

It is known that nutrient availability plays a significant role in soil fertility; organic and inorganic sources of essential nutrients are affected by several factors including transformation processes. These processes are controlled by the physical, chemical, and biological soil properties. Therefore, transformation of available forms into unavailable ones is always closely related to the given soil type.

Adaptive Nutrient Supply and Soil Cultivation Methods in the Upper Zone of Hillside Vineyards

Somló-hill is Hungarys smallest wine district; however, it produces some of the best white wines. Viticulture dates back about 2000 years in the district, and the climate is balanced. Former volcanic activity was an important factor in the development of the brown forest soils (Cambisols). Experiments were conducted in 2006–2008 in vineyards located in the upper zone (above 200 m sea level) of Somló-hill for studying the most adaptive and environmentally friendly soil cultivation and nutrient-supply methods. The following treatments were applied in four replicates: (soil cultivation experiment) SC1, natural grass cover; SC2, mechanical soil cultivation; and SC3, organic mulch (crop residues), and (nutrient supply experiment) NS1, unfertilized control, NS2, nitrogen (N) fertilizer (NH4NO3) 50 kg ha−1; and NS3, farmyard manure (34 tons ha−1). Main chemical soil characteristics were determined in the 0- to 30-cm and 31- to 60-cm soil layers at blossoming and grape ripening. Yield parameters (kg per m2, soluble solids g per 100 g juice, and titratable acidity, g L−1) were assessed at harvest. The experimental results suggested that covering the soil with crop residues resulted in the greatest yields, explained by the more favorable soil water conditions. Differences in yield parameters were significant in 2 of 3 years. Soil mineral N content also showed significant differences among treatments. Increased N requirement of crop residues and natural crop cover were suggested. Results of the experiments showed that both ammonium nitrate and farmyard manure resulted in increased grape yield compared to the unfertilized control. Maintaining adequate soil moisture levels (containing basalt debris with low humus content and shallow fertile layer with poor water management) and soil organic matter content is of great importance because other nutrients may be ensured by the weathering of basalt.