FIELD APPLICATION OF LIME-STABILIZED SLUDGE REDUCES SOILBORNE DISEASES AND PESTS: abstract only
P Fine, (1), A Gips, (1,3), L. Roded (1), M. Reuven (2), L. Tsror (4), Y. Oka (4), and Y. Ben-Yephet (2)
1) Institute Of Soil, Water And Environmental Sciences,
2) Institute Of Plant Protection
The Volcani Center, ARO.
3) Extension Service, Ministry Of Agriculture, Israel
4) Gilat Experiment Station, Israel
(free)
We employed lime-stabilized sludge (LSS), a pathogen-free, high pH product, in combination with NH4 fertilizer to reduce Fusarium oxysporum f. sp. dianthi, Verticillium dahliae, Rhizoctonia solani, Sclerotinia sclerotiorum, Sclerotium rolfsii, Streptomyces sp., and knot forming nematodes (Meloidogyne javanica) below detection limits in neutral or calcareous soils. Two field experiments are discussed below: (i) reducing F.o. dianthi and Fusarium-wilt in carnations, and (ii) reduction of Verticillium dahliae and Rhizoctonia solani in potatoes.
The elimination of fusarium-wilt in carnations was tested in field mini-plots (1-m2 each, with 32 carnation plants per replicate in 8 replicates/treatment) on a non-calcareous sandy soil that was heavily infested with F.O. dianthi. The 0-20 cm soil layer was amended with either NH4 (as (NH4)2SO4) or LSS (at 75 Mg/ha) or both. Six treatments were tested: no addition, LSS only, sludge only, and LSS plus NH4-N additions to 62.5, 125 and 250 mg/kg soil final concentrations. The LSS raised the pH of the soil solution above 10.5 at contact, to decrease below pH 9 within 20 days. Each of the 1536 carnation plants in the experiment was inspected for wilt symptoms in 2-week intervals from day 90 after planting to day 180 (harvest), and the harvested canopies were inspected for fusarium-related browning of the xylem. Soil samples were analysed for chemical parameters and for F.O. dianthi viability.
F.O. dianthi counts in the soil decreased at all LSS treatments, to nil at LSS + NH4-N at ≥125 mg/kg soil, and 160 days later, the count was still 12% of the original untreated. The occurrence of diseased plants (even the slightest extent was considered) decreased to 40% of the control.
The second field experiment was on controlling Verticillium dahliae and Rhizoctonia solani in potatoes grown on a heavily infested loamy loessial soil. The treatments were similar to above, in 6 replicates, 60 m2 each. All plots were covered with polyethylene for the first 3 weeks after LSS application and subsequent ploughing. Incidence of V. dahliae-infected plants was substantially reduced, from 52-68% of all control plants to 20-27% in LSS treatments. Similarly, colonization levels of V. dahliae were significantly reduced from 223 and 380 cfu/g in the control to 4-20 cfu/g in the LSS treated soils. R. solani incidence on daughter tubers also decreased from 11 and 21% in the controls to 2.3-6.9% in the LSS treatments. The reduction most likely resulted from NH3 toxicity to the soil-borne pathogens, boosted up at the high pH of the soil solution. Hence, application of high pH LSS in combination with NH4 fertilizer to soil can significantly reduce diseases caused by major soil-borne pathogens. This is in addition to the fertilizer and soil conditioning values of the LSS. Nonetheless, a wide commercial application still awaits better agro-technical tuning with respect to properties of soil and LSS, and better understanding of the interactions of the LSS-NH4 in pathogen(s) life cycle(s).
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