Pre-harvest desiccation of crops for conservation. 1. Effect of steam and formic acid on the moisture concentration of lucerne, ryegrass and tall fescue before and after cutting

Five experiments were conducted to determine the effect of pre-harvest treatment with steam or formic acid on the moisture concentration (MC) in crops of lucerne, two varieties of perennial ryegrass, tall fescue and Italian ryegrass. In each experiment, plots were treated with a mixture of hot gases and steam (S) or sprayed with an aqueous solution of formic acid (F). In the tall fescue experiment the F treatment was applied to the cut swath but in all other instances the F and S treatments were applied to the swards before cutting and the MC changes after treatment compared with those in untreated cut swaths (W 1). Twenty-four hours after initial treatment all S plots, and those F plots other than tall fescue, were cut and the subsequent water loss compared with that from (i) untreated material cut at the same time (W 2) and (ii) the W 1 plots cut the previous day. In all five experiments the change in the MC of the S plots was similar to that of the W 1 plots both before and after cutting. The reduction in the MC of the F plots before cutting was less than that of the S and W 1 plots, and in three of the five experiments water loss from cut F plots was apparently restricted in comparison with that from untreated cut material (W2). Neither desiccant treatment showed great promise as a pre-treatment to cutting for hay making although formic acid may have limited value when a crop is to be harvested directly for silage or artificial dehydration. In an appendix, the efficacy of using accumulated vapour pressure deficit as a basis for comparing the water loss from the untreated cut crops drying under different conditions is demonstrated.