Rainfall‐Induced Leaching and Leaf Losses from Drying Alfalfa Forage

Abstract

AbstractEfforts to construct models of forage yield and quality loss during the field drying of hay are hindered by a lack of quantitative information concerning several modes of loss. This study attempted to quantify leaching and rainfall‐induced leaf shatter from drying alfalfa (Medicago sativa L. ‘Magnum’) forage. A rainfall simulator was used to treat samples from four forage cuttings in 1989 and 1990 at four levels of tissue moisture between 760 and 150 g kg−1 (wet basis). Rainfall amounts of 0 (control), 5, 10, 15, and 20 mm were used at intensity levels of 20 and 40 mm h−1. Leaves lost due to rainfall were collected, samples of forage tissue were analyzed for quality and yield changes and samples of leachate water were collected from beneath hay samples for analysis. Results showed that leaf shatter is not directly induced by rainfall. Analysis of forage tissue showed that leaching of soluble dry matter caused dry weight losses and increases (P ≤ 0.05) in the proportion of fiber in tissue. Leachate analysis provided a more precise measure of leaching losses. Analysis of leachates for total dissolved and suspended dry matter demonstrated that leaching increases with rainfall amount and as tissue moisture levels decline. At 700 g kg−1 (wet basis) moisture, leaching losses reached only 0.3% of initial sample dry matter, while at 170 g kg−1 moisture they were as great as 1.7%. Leaching was also greater (P ≤ 0.05) under rainfall at 20 mm h−1 than 40 mm h−1. A regression equation generated from the leachate data can be used to model leaching losses within prescribed limits.