Predictability of compost-induced suppression of soil-borne plant diseases is poor. Part of the variability in disease suppression could be due to the heterogeneity of a given compost. Therefore, the disease suppressive properties of different wet-sieved fractions of two composts against three soil-borne plant pathogens were studied. The ability of a green waste and a yard waste compost to suppress the soil-borne plant pathogens Fusarium oxysporum f.sp. lini (host: flax), Phytophthora cinnamomi (host: lupin), and Meloidogyne hapla (host: tomato) was determined. The following compost fractions were prepared: 2-4 mm (40% v/v with peat-based substrate), 1-2 mm (35 or 45% v/v; comparable number of particles and comparable organic matter content as the 2-4 mm fraction amendment respectively), and 1-2 mm (35% v/v) obtained from the 2-4 mm fraction by a series of dry-sieving, crushing, and wet-sieving. The 2-4 mm compost fraction of both composts showed significantly higher disease suppression for the three pathosystems, except for P. cinnamomi with one compost, in which there was no effect. For both composts, oxygen uptake rate showed a significant positive correlation with disease suppression of all pathogens except for P. cinnamomi. For the composts studied, substrate quality as expressed by oxygen uptake rate, seems to be of greater importance for disease suppression than compost particle size per se.
The yield of seven medium-grain rice varieties was determined in bimonthly plantings at Gurabo. Chontalpa 16, Brazos, and Vista were the highest yielding varieties averaging 5,700 kg of rough rice/ha, but yields of Brazos varied more with season of the year. Yields were highest for February plantings and lowest for October plantings, followed by those for August. Similar yields for all seven varieties averaging about 5,100 kg/ha, were produced when the rice was planted in April, June or December. Varieties and season of the year affected the time required from planting to harvest, which averaged from 101 to 125 days. Lodging was most prevalent in the August plantings, averaging 34%. Nato and Saturn were the most prone to lodging, averaging 21 and 43%, respectively.
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