Asparagus spear size distribution and earliness as affected by water and nitrogen applications

ABSTRACT Green asparagus production is affected by water and nitrogen applications, and soil and air temperatures. Reduced water and nitrogen applications lowered the total yield for the 60-day harvest. Nitrogen deficiencies, to a greater extent, reduced the number of spears produced than did lower water application levels. Average spear weight was increased with optimum applications of water and nitrogen. Low water applications changed the spear size distribution which resulted in the production of smaller spears compared to treatments receiving greater amounts of water. Low nitrogen levels also changed the spear size distribution compared to optimum or greater nitrogen levels and also reduced the total yield for all harvest periods. Asparagus production early in the harvest season (0-20 days) was reduced for low nitrogen treatments when soil temperature was lowest. The rates of production were constant for all water and nitrogen treatments from day 20 through day 60. All asparagus size classes showed an increase in yield for the first 30 harvest days. After 30 days the production of larger spears decreased for each successive harvest interval, while the production of smaller spears remained constant, and then showed a large increase during the last harvest interval.