The relation between moisture content and moulding in cured hay.
Samples of cured hay have been stored in closed containers at relative humidities of 0–95% at temperatures varying from 5 to 25° C. A curve relating equilibrium moisture content to relative humidity of the store has been constructed and the incidence of first mould growth noted. An explanation has been suggested to account for the apparent discrepancy between earlier published work concerning the onset of moulding and conditions normally prevailing on the farm. In laboratory storage experiments temperature conditions are relatively constant, whereas with hay stacked in the open air the high atmospheric humidity in winter is offset by a lowered temperature, and the higher summer temperature is accompanied by a lower moisture content in the hay.
Role of Water Activity in the Spoilage of Alfalfa Hay
Abstract Moisture sorption isotherms of alfalfa stems and leaves obtained from the first and third cutting of the season were constructed. Important differences in the relationship between moisture content and water activity values for alfalfa stems and leaves were observed. The extent of those differences was influenced by the initial moisture content and maturity of the alfalfa plant. Water activity, not moisture content, determined the nature of fungal growth on alfalfa stems and leaves. At water activity of 1.0 (moisture content, 51.7 to 65.3%), fungal growth was characterized by extensive mycelial development. Reducing the water activity to .93 (moisture content, 28.1 to 41.7%) dramatically increased fungal fruiting body development and reduced mycelial development. Even though alfalfa stems are nutritionally inferior to alfalfa leaves, fungal fruiting bodies appeared sooner on the stems at water activity values less than .81. Addition of a rich nutrient source, yeast extract, to the stems and leaves did not change that relationship. Analysis of the experimental results reported showed that alfalfa stems have a greater spoilage potential than alfalfa leaves. Implications of these findings to the spoilage process and the nutritional quality of baled alfalfa hay are discussed.
Investigations on the rôle of organic matter in plant nutrition
1. As the result of decomposition of green manure in a swamp soil, the coarse fractions (including coarse and fine sand) of the surface layer (first 3 inches) decreased by 11·2 per cent. while the fine ones (silt+clay) increased by 9·8 per cent. in the course of 43 days. The effect was less pronounced in the manured soil maintained at 60 per cent. saturation, while no alteration was to be noticed in the case of the unmanured specimens. 2. Treatment with dilute hydrochloric acid prior to dispersion had no appreciable effect on the estimates of mechanical composition obtained in the different cases. Loss in solution was also comparatively small. 3. The silica-sesquioxide ratio increased slightly as the result of decomposition of green manure in swamp soil. The composition of the fine fractions was also altered, the total percentages of the oxides of iron, aluminium and silicon increasing from 90·5 to 99·3 in the course of 71 days. 4. The practical significance of the above and related observations has been discussed.