CALCIUM-AMMONIUM EFFECTS ON GROWTH AND YIELD OF SMALL GRAINS

Calcium (Ca++) is known to stimulate potassium (K+) and ammonium (NH4) absorption rates by plants. Increased NH4+ absorption stimulates pla nt growth and development. However, little is known about the effect o f Ca++ with NH4+ on small-grain crops. The objective of this research was to examine the effect of Ca++/NH4+ on growth and development of wh eat (Triticum aestivum L.), oat (Avena sativa L.), and barley (Hordeum vulgare L.). Treatments consisted of growing small grains using compl ete nutrient solutions with a molar ratio of 0, 0.30, 0.60, 1.20 and 1 .80 Ca++/NH4+, and a check with NO3--N. Plants were grown in the green house to seedling (30 d), intermediate (elongating, 60 d), and mature (booting, 90 d) growth stages on a NO3- nutrient solution and then tre ated for 7 d with the Ca++/NH4+ fertilizer solutions. One set of plant s was fertilized solely with the Ca++/NH4+ solution and another with a NO3- fertilizer solution. The addition of Ca++ with NH4+ to small gra ins resulted in increased N absorption, grain yield, tiller formation, dry matter, and grain weight per unit of plant dry matter, but the ext ent varied with the crop. Calcium apparently caused a redirection of f oliar metabolites to grains. Short-term treatments with Ca++/NH4+ at d ifferent growth stages showed the least results at the seedling stage, whereas maximum results were obtained at the intermediate growth stag e (initiation of jointing) and good stimulation of plant growth and ti llering at the mature (booting) stage. Calcium increased NH4+ absorpti on, leading to increased tillering, increased weight per head of grain produced, and consequently higher grain yields. Calcium added with NH 4+-N increases plant N use efficiency by more rapid absorption, greate r rates of tillering, greater metabolite deposition in seeds, and poss ibly increases in photosynthesis.