Performance of Coffee Seedlings As Affected By Soil Moisture and Nitrogen Application.

Nitrogen (N) and soil moisture are the most important factors controlling yield in Colombian coffee crops. Since long-term productivity is contingent on early growth, it is imperative to study these factors in seedlings in order to ensure maximum yield potential of trees. A greenhouse experiment with four soil water and four N levels was used to determine how these two important variables affect quantifiable parameters representing seedling performance. Shoot biomass, the most obvious indicator of performance, was increased by both higher soil moisture and higher N application, although the root:shoot ratio diminished with increasing N application. Like shoot biomass, leaf N content also increased with increasing N application, with relatively more leaf N recovered from fertilizer as soil moisture increased. Water use efficiency, in terms of shoot mass produced per unit of evapotranspired water, responded dramatically to N level but was not affected by soil moisture. The strong effect of N application on water use efficiency was affirmed by the higher 13C/12C ratios of plants grown under higher N levels, indicating greater water stress in these plants. All of these responses are associated with changes in photosynthetic metabolism as a result of acclimation to the imposed conditions. We aim to generate new recommendations for maximizing growth of coffee seedlings, by increasing the use efficiency of critical resources while at the same time reducing economic and environmental impacts attributed to N fertilizers.

Keywords: soil moisture, coffee crops, biomass, ¹³C composition, N recovered from urea