Péter Csathó

Two Worlds within EU27: Sharp Contrasts in Organic and Mineral Nitrogen- Phosphorus Use, Nitrogen-Phosphorus Balances, and Soil Phosphorus Status: Widening and Deepening Gap between Western and Central Europe

In the first section of the article, factors affecting the magnitude of mineral and organic nitrogen–phosphorus (NP) use, such as per capita gross domestic product (GDP) and population density, are discussed. Nutrient balances, especially those of N and P, are important environmental indicators. In recognition of their importance, the countries belonging to the Organization for Economic Co‐operation and Development (OECD) group have an obligation to submit yearly calculations on soil surface N and P balances. The NP balance studies should always be combined with investigations on the distribution of soil NP status of the investigated area. The negative NP balances and worsening NP status in central‐ and eastern European (CEE) countries, including those that have recently joined the European Union (NEU12), are in sharp contrast to past practices in the EU15 countries, where strong positive NP balances and oversupply of NP may lead to environmental and ecological threats. There is evidence that the level of oversupply in many of these countries is on the decline. In the CEE countries, on the other hand, worsening levels of NP undersupply may result in increasingly low yields and in economic and agronomic problems. Cooperation within the European Union should help to solve both the environmental threat facing the western part of the community and the agronomic and economic problems in the central and eastern parts. Fertilizer recommendation systems should function on the principle of providing sustainable and economically sound NP nutrition for crops without threatening the environment with the NP oversupply. In a perfectly correct and justifiable manner, the European Union made investments in environment protection, a strict condition for the accession of the central European countries to the EU. One essential obligation was the satisfactory disposal of sewage, as a water‐protection measure. The EU should be as consistently strict in curbing the massive diffuse NP pollution caused by agriculture. Improvement of the EU Nitrate Directive and elaboration of the new EU Phosphate Directive should be based on environmental risk assessment. The principles of environmentally friendly crop nutrition should appear in the improved EU Nitrate Directive and in the new Phosphate Directive. The EU countries with higher per capita income and population density should be given special attention because of their environmentally friendly crop nutrition practice.

New environmentally friendly fertiliser advisory system, based on the data set of the Hungarian long‐term field trials set up between 1960 and 1995

Abstract Following the 25‐year intensive fertilisation practice in the country, two‐thirds of Hungarian soils became well or very well supplied with phosphorus (P) and potassium (K). As a consequence of both political and ecological changes in the late 1980s and early 1990s, fertiliser subsidies were withdrawn, and nitrogen (N) use has dropped to one‐fifth, one‐third, P and K use to one twenty‐fifth, one‐twentieth of the amounts used in the early‐mid 1980s. An enormous demand has risen for a new, cost saving, and environmentally friendly fertiliser recommendation system. The new system based on the results of the published long‐term field trial data in the period of 1960–1995 faces the new challenges.

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.

The residual effect of K fertilization in a Hungarian corn monoculture long-term field trial, 1990-1999

Hungarian agriculture is still living on the residues of previous K (and P) applications, but these reserves are becoming smaller and smaller. It is essential to know how long the previous K application provides adequate K for crop as a function of residual effects. Corn (Zea mays L.) is considered as a potassium-demanding row crop. The K-exhaustion long-term field trial with 0, 240, 480 and 960 and 1440 kg initial build-up K2O doses/ha was established in the autumn of 1989, on a light loam calcareous Mollisol, having 23% clay content, with Illite clay mineral dominance. The soil is moderately supplied K. Corn as test plant was sown in monoculture in the trial. The first 10 years are evaluated in the paper. Soil K-test/AL-K/values did not decrease in the first 6 years, but diminished in the 7–10th years. The light loam soil did not fix the added fertilizer-K strongly. Yield losses, due to K-shortage, started when AL-K values dropped below 150 mg K kg−1 soil. The 1440 kg K2O/ha initial dose provided appropriate corn yield levels for 10 years, the 960 kg dose for 6 years, the 480 kg dose for 4 years, and the 240 kg dose for 1 year, on this soil, originally moderately supplied with potassium. The residual effect of build-up K doses was measurable even after the 10th year. Weather conditions, i.e., the amount and distribution of rainfall during the vegetation period, affected strongly the magnitude of residual K effects. Both the AL-K test values, and flowering stage leaf K concentrations indicated the soil and plant K supply in the different K levels and years similarly. Residual K effects can be hindered by different reasons in the first years: due to previous K application in the experimental area, or drought period, or efficient utilization of soil-K by hybrids. Soil and plant K analyses data are useful tools in adapting the results of long-term field trials for developing fertilizer recommendations.

Comparative Effects of Rock Phosphates on Arbuscular Mycorrhizal Colonization of Trifolium pratense L.

Abstract The effect of five rock phosphates with different solubility (from Algeria, North Florida, North Carolina, Senegal, and Morocco) and that of single superphosphate (SSP) alone or with lime was investigated on the root colonization of red clover with indigenous arbuscular mycorrhizal fungi (AMF). In a pot experiment, the phosphorus (P) sources were applied at four rates (0, 100, 400, and 1600 mg total P2O5 kg−1 dry soil) to an acidic sandy soil (Nyírlugos) and to an acidic clay loam soil (Ragály). The arbuscule content of the roots was more sensitive to various rock phosphates than the infection frequency. No mycorrhizal colonization of roots was observed in the Nyírlugos soil at the 1600 mg P2O5 kg−1 level of SSP or in either soil at the 1600 mg P2O5 kg−1 level of SSP+lime, indicating that the mycorrhizal dependency of the host was eliminated by the highest soluble P concentrations in the soil.

Long-term field evaluation of phosphate rock and superphosphate use strategies in acid soils of Hungary: Two comparative field trials

The effect of two P-forms and the P fertilization system were studied in field trials set up on two moderately acidic Hungarian soils. Reactive Algerian rock phosphate and Kola superphosphate doses were based on the phosphorus equivalence. The experimental design makes it possible to compare the effect of annual 35 kg/ha P doses with initial one-time application of the 175 kg/ha P level in a five-year interval. Ammonium-lactate (AL)-, NaHCO3 (Olsen)- and DW-P contents as well as Lakanen- Erviö (LE)- soluble Cd, Cr and Sr contents were also determined. The results of the first five-year period are reported in the paper. Responses to P fertilization were related to the original P supply of the soils. There was no significant difference between the two P forms and between the P fertilization systems on both grain yield and P-uptake. While AL- method overestimated, and Olsen-method – on the other hand – underestimated the P supply of reactive Algerian rock phosphate, distilled water (DW)-soluble P contents indicated the soil P status more accurately. Phosphorus balances were positive after the fifth year of the trials in the P treated plots. The soluble Cd and Cr contents did not increase in the Algerian rock phosphate treated plots. On the other hand, Kola superphosphate application at 175 kg/ha P level resulted in higher LE-Sr contents in soils. The Algerian rock phosphate is an economic alternative P source on the moderately or strongly acidic Hungarian soils.

Evaluation of Different Fertilizer Recommendation Systems on Various Soils and Crops in Hungary

The World Phosphorus Institute (IMPHOS) financed a 3‐year program for the testing of various Hungarian fertilizer recommendation systems [the four levels of the new Research Institute for Soil Science and Agricultural Chemistry (RISSAC)–Agricultural Research Institute (RIA) system, the Talajerőgazdálkodás integrated soil fertility management system, and the intensive MÉM NAK system developed in the late 1970s by experts from the Ministry of Agriculture and Food] when applied to three major crops (winter wheat, maize, spring barley) grown on three characteristic Hungarian soils (brown forest soil, chernozem, meadow soil). The first six treatments in the experiment represented a classical deficiency experiment, aimed at checking the correctness of the nitrogen–phosphorus–potassium (NPK)–supplying categories determined by the various systems. On all three soils and for all three crops, the IMPHOS experiments confirmed the basic principles of the new cost‐saving, environmentally friendly RISSAC‐RIA fertilizer recommendation system and the correctness of the methods used for calculating fertilizer rates. The new RISSAC‐RIA system resulted in good yields, on par with those obtained using the intensive MÉM NAK system, with total NPK rates that were sometimes as little as 40–60% of the intensive recommendations. Consequently, the greatest incomes per unit area were also achieved using the recommendations given by the new, cost‐saving, environmentally friendly RISSAC‐RIA system.

Effect of Five Phosphate Rocks on Red Clover (Trifolium pratense L.) Yield in Pot Trial

Abstract Phosphorus (P) availability in five phosphate rocks with different P solubility was compared with that in single superphosphate and superphosphate+lime in a pot experiment with red clover as test plant on a Lamellic Arenosol with sand soil texture and on a Haplic Luvisol with clay loam soil texture, both strongly acid with low P supply. Phosphorus rates in the pot experiment were 0, 100, 400, and 1600 mg total P2O5 kg−1. On both soils, there was a weak correlation between total added P and red clover P responses. If P solubility of the PRs was also taken into account, the correlation between formic acid–, citric acid–, or neutral ammonium citrate–soluble P amounts added and red clover responses became much stronger. Soil P availability was estimated by water, Olsen, Lakanen‐Erviö, and ammonium lactate tests. Among the P extractants studied, Olsen soil P test gave the best correlation with red clover yields.

Sustainable Agricultural NP Turnover in the 27 European Countries

A deep contrast of NP balances, water nitrate contamination, soil P and rural development has appeared between Western and Eastern European countries since the implementation of the European nitrate directive in 1991 (91/676/EEC). In an economy ruled by free market rich countries become richer and poor countries become poorer from the point of view of water nitrate contamination and soil P overloads. There is a need for a paradigm shift in the European agro-environmental protection legislation. Instead of speaking about it, agro-environmental protection, social, and rural development principles should gain real priority. According to the principle of subsidiarity, the present problems can be solved only at the highest European-level, i.e., in the legislation and in the administration.

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.