WHAT IS A CORRECT PLANT-DENSITY FOR TRANSPLANTED GREEN ASPARAGUS

We demonstrate a quantitative framework for the study of yield-density relationships of transplanted green asparagus (Asparagus officinalis L.). Such a framework is essential if new research is to make effectiv e use of what is already known. We used quadratic equations to analyse data from 15 yield-density studies with transplanted asparagus, in or der to get indications of appropriate densities for new plantings in N ew Zealand and Western Samoa. In all instances the optimum density was close to or above the highest density used in the trial, so that opti ma were often poorly defined. We work with the density which gives 90% of the estimated optimum yield, which for practical application may b e more realistic than the density which gives optimum yield. We give d etails of the methodology used for these estimates. Estimates of this 90% optimum, based on the cumulated yields over the first 3 years, var ied from 8500 to 66000 plants/ha. The optimum planting density estimat ed from cumulated yields to Year 3 gave an accurate estimate of optimu m planting densities for cumulated yields to Year 7, and were substant ially better for this purpose than cumulated yields to Year 2. No clea r picture emerges of factors which may affect the optimum plant densit y for transplanted green asparagus, which clearly varies widely. There are too many factors which vary in an unsystematic manner between the different studies which we describe, or for which no information is g iven. We highlight deficiencies in trial planning and/or reporting whi ch compromise the attempt to place individual trial results within a w ider context. We make proposals for the conduct and reporting of futur e studies, which if followed will make the systematic overview of futu re trials more straightforward and productive.