Evaluation of N recommendations for maize-sesame association in the Southwestern Coastal Plain of Guatemala

Growers in the Southwestern Coastal Plain of Guatemala routinely fertilize maize/sesame association according to their experience. All of them use N fertilizer, whereas only some also apply P and K. This project was conducted in 2014 to compare the responses of maize and sesame in 10 locations to N recommendations provided by three sources.

Most topsoils were clayey, with pH and organic matter between 6.1 to 6.9, and 1.8 to 3.2%, respectively. Mehlich3-P concentrations were extremely low (below the detection limit). Soil test B was low to very low in all samples, whereas S was low in 70% of the samples. Soils of two locations were low in exchangeable K and in one location soil test Zn was low. The three N recommendation sources were: NuMaSS (an expert system), a private adviser, and the farmer. Recommendations also differed in the amounts of P, K and S applied. NuMaSS was used to estimate only N, leaving P, K and S rates equal to normal farmer’s rates. Nitrogen by NuMaSS was split into around 25% at planting, and the rest into two applications, 20 and 40 days after sowing. The amounts, sources, and split of N, P, K, and S recommended by the adviser were constant across all locations. There were wide differences in the amounts, sources, and split of N, P, K, and S used by growers.

No statistical differences could be detected both for maize and sesame yields between recommendation sources. Crop performance was limited by drought and excess water during maize and sesame growth, respectively. Foliar analyses identified B and Mg as the most limiting nutrients.