The cumulative effect of spent mushroom compost on some chemical properties of the soil under potato cropping conditions

Abstract. This work was carried out in the summer of 2020 to take an advantage of the spent mushroom compost SMC for the potato cropping and improving soil fertility towards reducing the excessive use of chemical fertilizers, which are commonly used in the traditional methods of growing potatoes, and considered as a source of contamination of the groundwater and streams and raise the cost of production. This experiment was designed by the application of SMC in the cultivation of potato crop var. Spunta, in the bedding medium, at increasing gradual rates (0, 25, 50, 75 and 100%, v/v), to be compared with soil and organic manure mixed with chemical fertilizers as an ideal treatment. The effect of the above-mentioned levels of SMC on soil fertility was very clear, where the results did not show any negative impact on soil properties in spite of its high recorded salinity (EC1/1 = 9.53 dS.m -1) and tended to retain soil fertility through increasing its contents of organic matter OM and nutrients before and after potato crop cultivation. The lowest level of compost 25% SMC, increased the concentration of OM in the soil to 18.4% compared with 4.5% in the control, and raised N concentration in the soil from 0.3% in the control to 1.8% in the treatment 100% SMC before planting. The cumulative effect of OM in the soil after harvest has risen from 3.3% in the control to 12.6% in the treatment 25% SMC, and N content from 0.15% for the control to 1.05 % for treatment 100% SMC. But the cumulative effect for available P in the soil was not positive because of lime effect and consumption in the growth and production process. Also, K did not show a clear cumulative effect because of the richness of the soil before and after planting and its high ability for loss in the organic soil by leeching.