EFFECT OF SOIL FATIGUE PREVENTION METHOD ON THE MICROBIOLOGICAL SOIL STATUS IN REPLANTED APPLE TREE ORCHARD PART I. NUMBER OF NEMATODES

Eugeniusz Pacholak¹, Krzysztof Rutkowski¹, Zofia Zydlik², Marcin Zachwieja^1
1 Department of Pomology, University of Agriculture in Poznan, Poland
² Department of Pomology, Poznań University of Life Sciences, Poland

ABSTRACT

The studies were carried out in orchard of the Agricultural and Pomicultural Experimental Farm in Przybroda owned by the Agricultural University of Poznań.

On the area of the replanted orchard, the occurrence of 8 nematode families or types was identified in a very diversified number. Temik was the only one that limited significantly number of nematodes both from the genus Pratylenchus and from the other genera and families. The total number of nematodes depended on the applied soil moisture level. The most safe locality under apple-tree orchard regarding the number of harmful nematodes was a soil where apple trees never had been grown before.

Key words: apple trees, replant soil, nematoda.

INTRODUCTION

The problem of tree growth disturbances in the initial period of replanted orchard management can be caused by many factors. One of them is the accumulation of parasitical nematodes in soil [3].

Damages are caused by nematodes belonging to the order of Tylenchida and Dorylalmida which prick plant tissues and introduce into them digestive enzymes. It weakens the root system unsettling biochemical balance [2]. Particularly dangerous is the feeding by nematodes in young orchard where the root system is poorly developed. In consequence it leads to growth inhibition and delays the term of first fruiting.

Species composition, development and the harmfulness of nematodes depend among others on such factors as soil type, content of organic substance, climate, rootstock reaction, growing system [8, 9, 11, 14].

The aim of the studies was the estimation of the effect of soil fatigue prevention methods on the species composition and the number of nematodes in a replanted orchard.

MATERIAL AND METHODS

The first orchard was established in 1976 using James Grieve cultivar on A 2 root-stock with M26 insertion in (2+2+3)×2 m spacing. In 1988, the first replantation took place when Idared cv. trees were planted on MM 106 rootstock in (2+2+3)×2 m without any tillage. After 2nd replantation in 1994, an essential growth decrease and soil fatigue was observed in the orchard. Therefore, in 1998, trees from control combination were removed where no fertilization was applied for the past 22 years and within each irrigation level, 6 methods of replantation disease prevention were applied. On plots where trees were dug up, one-year shoots of Elstar cv. were planted on M.9 rootstock in 3.5 m × 1.5 m spacing. Trees were planted into holes of 0.6 × 0.6 × 0.6 m (0.216 m³) without any tillage. Side walls were lined with plastic foil.

Irrigation levels:

W₀ – without irrigation, soil moisture was maintained at the level of natural atmospheric precipitations,
W₁ – irrigation was applied for maintaining soil moisture at the level of -0.03 MPa of water potential;
W₂ – irrigation was applied for soil moisture maintenance at the level of -0.01 MPa of water potential.

Combinations with methods preventing replantation disease:

Each combination was in 4 replications and there was one tree in each replication.

In the first year, equal nitrogen fertilization in a dose of 5 g N/m² was applied.

Soil samples for the analysis of nematode number were collected at the end of May from the arable layer, where the greatest number of capillary roots was found. From each replication, 500 g of soil were collected separately in 4 replications.

Quantitative analysis of nematodes number was carried out in Nematology Department of Plant Protection Institute in Poznań by centrifugal method in a sample of 200 cm³ of soil.

The obtained results were subject to multifactor analysis of variance using the program Statistica 7.0 PL. Significant differences were estimated at the level of α = 0.05.

RESULTS

Nematological analysis carried out in the years 1999-2004 showed the presence of 8 taxonomic groups of nematodes (tab. 1). In the year when the study was started, there was the greatest number of nematodes, and in the following years, a systematic drop in their number was noticed (tab. 2). The most numerous were the nematodes from Belondaimidae family and their number depended on the applied soil fatigue prevention methods. The greatest number of nematodes was found in the soil of control combination and significantly lower was the number in virgin soil. Irrigation also had an influence on nematode number from this family. The maintenance of soil moisture at the level of -0.30 MPa of water potential decreased the number of these nematodes.

Nematode genus characterized by a high harmfulness in relation to fruit trees is Pratylenchus which was represented by three species: P. penetrans, P. neglectus, and P. coffeae. Depending on the method of soil fatigue prevention, the number of this genus oscillated between 1.8 and 19.1 individuals in 200 cm³ of soil. The applied irrigation caused an increase of Pratylenchus nematodes and their number ranged from 9.9 pcs to 14.2 pcs (W1) (tab. 1).

The third group of nematodes regarded as to the harmful ones for fruit trees were the representatives of Tylenchidae and Trichodoridae families. The number of these nematodes depended on the applied soil fatigue prevention methods and also on the irrigation method which did not significantly affect the number of nematodes from Tylenchidae family, on the other hand, the number of nematodes from Trichodoridae family increased (tab. 1).

Furthermore, in result of analyses, the occurrence of other nematodes was found. They belonged to genera Aphelenchus, Aphelenchoides, Paratylenchus from Criconematidae family, but they are not regarded as the harmful ones for orchard plants and they occurred in a small number. The applied treatments for soil fatigue prevention and soil moisture maintenance decreased their number during the experimental period (tab. 1).

The greatest number of harmful nematodes during all years of studies were found in the control combination, i.e. in the soil which since 1976 had been continuously planted with apple trees (tab. 2).

The analysis of the total number of harmful nematodes in 1999-2004 and the effect of the applied soil fatigue prevention methods (tab. 2), indicated a high effectiveness of Temik 10 G in the reduction of the number of harmful nematodes in the soil as compared with the soil where apple trees had never been grown.

Application of Alliette 80 WP, ammonium phosphate or peat did not exert any significant effect, in comparison with the control combination, on the change in the number of harmful nematodes (tab. 2).

Irrigation had some effect on the number of harmful nematodes in the soil (tab. 3). It was found, that with an increase of soil moisture, there increased also the number of nematodes, and their number was the greatest when moisture was maintained at the level of 0.03 MPa (W₁). It must be stressed that the number of harmful nematodes was the highest in the first years after replantation and it systematically decreased in the successive years (tab. 2, 3).

DISCUSSION

Soil fatigue in the studied orchard had been found already earlier [9]. However, an unequivocal answer to the question what was the direct cause of this phenomenon was significantly more difficult. Replantation disease is in most cases connected with a complex of abiotic and biotic factors [1, 13] and one of the main reasons is the accumulation in the soil of parasitical nematodes [5, 6, 7, 9, 10, 12].

Soil on which apple trees had been grown for the past 25 years was characterized by a significantly greater number of nematodes in comparison with the number of nematodes in a virgin soil. The application of Temik 10 G preparation significantly reduced the number of nematodes. The maintenance of soil moisture at the level of -0.03 MPa contributed to the increase of nematodes number; with an increased intensity of irrigation (-0.01 MPa) their number decreased.

The opinions of Kirkpatrick et al. [4] and Zepp [15] have been confirmed that with the age of trees and with adequate agrotechnics the number of harmful nematodes can be reduced. A significant drop of nematodes number was found in replanted orchard in the successive years of orchard management.

CONCLUSIONS

1. Apple trees cultivated for many years caused an increase of nematodes which in the first years after replantation was one of the factors of replantation disease. The most effective method of soil fatigue prevention in the control of harmful nematodes has proven to be Temik 10 G.

2. The total number of nematodes depended on the age of orchard and the applied soil moisture level. With the age of orchard, the number of nematodes significantly decreased and the highest nematodes number was when moisture was maintained at the level of -0.03 MPa.

3. The safest locality under apple-tree orchard regarding the number of harmful nematodes was the soil where apple trees never had been grown before.

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The research work was financed from the grant (No 5PO6C019) sponsored by the Ministry of Finances and Informatics Implementation.

Accepted for print: 13.12.2006

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