Marianna Magyar

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.

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.

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.

Nitrogen and phosphorus balances of hungarian farms as management tools for sustainable agriculture

Abstract At the moment, Hungarian agriculture is confronted with a certain duality as far as nutrients are concerned. On the one hand, national soil nutrient balances show substantial deficits, and on the other hand, agricultural nutrient use is responsible for a part of the nitrogen (N) and phosphorus (P) losses to the environment. To understand this duality and help optimize farm nutrient management, the farm gate N and P balances of 12 farms, representing a variety of Hungarian agriculture, were calculated for the year 2002. The farm gate N and P surpluses/deficits in the east of the country were lower than in the west. This was correlated with a lower fertilization rate. The low soil fertility level due to a prolonged period of low fertilization in combination with continuing nutrient deficits can lead to possible future reduction in crop yields.

Evaluation of Agronomic and Environmental Soil P Test Methods in a Network of Hungarian Long‐Term Field Trials

Abstract Winter wheat shoot weight and phosphorus (P) concentrations, corn leaf weight and P concentrations, and soil AL, Olsen, H2O, Bray 1, Pi (Fe-oxide impregnated paper strip) and AERM (anion exchange resin membrane) contents were determined in a network of uniform Hungarian national long‐term field trials. P application had a significant effect on soil P test values at different P levels and sites. The relationship between the different soil P test methods was studied separately for different soil groups (all, acid, and calcareous soils). Corn leaf weight was influenced by the sites much more than by soil P supply level, whereas corn leaf P percentage was influenced by both sites and P levels. For winter wheat, both sites and soil P levels had a positive effect on wheat shoot weight. Wheat shoot P percentage was influenced by the soil P supply much more than by the sites. Correlation between corn leaf P percentage and the Pi or AERM extractable P and between wheat shoot P percentage and the Pi and AERM P values was logarithmic.

Effect of Phosphate Rocks on Spring Barley Shoot Yield and Phosphorus Uptake in a Pot Trial

The effect of five rock phosphates (from Algeria, Florida, North Carolina, Senegal, and Morocco) and hyperphosphate on the shoot yield, phosphorus (P) concentration, and P uptake of spring barley was studied in a pot experiment on acidic sandy soil (Nyírlugos) and acidic clay loam soil (Ragály), with superphosphate as the standard P source. The effect of adding calcium carbonate (CaCO3) in combination with superphosphate (SSP) was also investigated. Averaged over the whole experiment, the shoot yield of barley was almost twice as high (3.69 g pot−1) on the clay loam soil from Ragály, which was rich in colloids, than on the colloid‐poor sandy soil from Nyírlugos (1.90 g pot−1). The P uptake, however, was only 25% higher (13.0 mg P pot−1) on the clay loam soil, averaged over the whole experiment, than on the sandy soil (10.4 mg P pot−1). This could be attributed to the fact that the P concentration of barley at tillering was almost 0.1% higher on average in the rock phosphate treatments and 0.2–0.3% higher in the SSP and SSP + CaCO3 treatments on the acidic sandy soil. On both soils, diverse P effects were observed in response to rates of 0–100–400–1600 mg total phosphorus pentoxide (P2O5) kg−1 of the different rock phosphates, adjusted on the active agent equivalence principle. The differences between the P effects, in terms of both biomass surplus and P uptake, exhibited a close correlation with the differences in the P solubility of the rock phosphates. On both soils the greatest biomass surplus and P uptake were recorded for the Algerian rock phosphate, which had excellent natural solubility. Hyperphosphate and the rock phosphates from Morocco and North Carolina were also efficient, whereas the other extreme was represented by the rock phosphates from Senegal and Florida, which had low specific surfaces, P solubility, and lime content. The differences between the rock phosphates could also be expressed in terms of relative agronomic efficiency (RAE %), when the effect of the rock phosphate was compared to that of water‐soluble P fertilizer, in the case of SSP. Averaged over the two soils and over the RAE% calculated on the basis of shoot yield or P uptake, the order obtained for the relative agronomic efficiency of the rock phosphates was the same as that observed for the solubility of the rock phosphates in neutral ammonium citrate. On both soils, the loosest correlation between rock phosphate solubility and either the shoot yield of spring barley at tillering or the P uptake was obtained when the P rates were calculated on the basis of total P content, and the closest correlation was obtained when they were calculated on the basis of the P fraction soluble in neutral ammonium citrate. This, together with the ranking of the rock phosphates on the basis of relative agronomic efficiency, suggests that under conditions similar to those of the present experiment, neutral ammonium citrate is the best solvent for determining the relative P solubility of the rock phosphates. When the effects of the various rock phosphates on the P uptake of spring barley were investigated, a close correlation was detected on both soils between differences in P effects and differences in various properties of the rock phosphates (P solubility, specific surface, CaCO3 content).