|FAGERIA, N - Embrapa|
Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2015
Publication Date: 3/10/2017
Citation: Baligar, V.C., Fageria, N.K. 2017. Nitrogen forms and levels influence on growth and nutrition of cacao. Journal of Plant Nutrition. 40:709-718.
Interpretive Summary: Cacao in tropical South America is grown on a wide range of infertile acid soils. On these soils, a lack of an adequate supply of nitrogen fertilizer greatly affects the growth and development of cacao. In this study we evaluated the type and amount of nitrogen fertilizer on various growth parameters of cacao. Irrespective of type of N fertilizer used, the different levels tested had no significant effect on plant growth parameters. However, the ammonium form of nitrogen fertilizer improved the growth of cacao better than either nitrate or a mixture of ammonium and nitrate. The different forms of nitrogen fertilizer also affected the influx, transport and use of macro-micronutrients in cacao. This information will be useful to cacao growers and extension workers in formulating nitrogen fertilizer use to improve cacao sustainability on infertile acidic soils of South America.
Technical Abstract: Ammonium and nitrate are the major forms of N present in tropical soils. A climatically controlled growth chamber experiment was conducted to assess the influence of forms (NO3-, NH4+, and mix of NO3- + NH4+) and levels (1.5 to 12.0 mM) of N on the growth and nutrition of cacao (Theobroma cacao L). Plant growth parameters were significantly influenced by N forms and nitrogen supplied as NH4+ proved better for the growth of cacao compared with NO3- form and mixtures of these two forms. Among macronutrients, maximum uptake by cacao was of K and minimum uptake was P and among micronutrients maximum uptake was of Mn and minimum uptake was of Cu. Nutrient efficiency ratios (shoot dry matter produced per unit of nutrient uptake) for macronutrients were S > P > Ca > Mg > N and K and for micronutrients NER were in the order of Cu > B > Zn > Fe > and Mn.