Maize production as affected by sowing date, plant density and row spacing in th Bolivian Amazon.

Slash and burn methodology is traditionally practised in thedepartment of Pando (Bolivian Amazon).The main crops sowed soon after theslash are maize, rice, cassava and common beans. Two separate field experimentswere carried out in 2008-2009 to determine the agronomic responses of maizeto sowing date, plant population and row width. For the first experiment a split-plot design was used. Maize cultivar (Bayo Blando and Perla Pandino) wasconsidered as main plots and the date of sowing as subplots. For the secondexperiment a split-split-plot design was used. Row spacing (0.5, 0.7 and 0.9 m)was considered as main plot, maize cultivar (Cubano Amrarillo and PerlaPandino) as subplots, and plant density (5.0, 7.5 and 10 plant m-2) as sub-subplots. A significant reduction of grain yield was observed as the date ofsowing (DS) delayed. Yield reduction of the second DS compared to the first,was 85 and 45% for Perla Pandino and Bayo Blando respectively. Theimportance of plant density as a function of the correct row spacing is clearlyshown. With the row spacing in use in the considered area (0.9 m) and with thenarrowest (0.5 m), the best yields were obtained with 10 plants m-2(5.5 t ha-1).The following conclusions can be drawn from the present study: 1. A delay inthe sowing date for maize by 15-20 days (compared to sowing immediately afterthe cutting of the virgin forest or the secondary forest) strongly reduces grainproduction. The cultivar Perla Pandino was the most susceptible with areduction of 85%. Late sowing of maize (mais de socorro), is suitable only ifintercropped with other crops in order to protect the soil from erosion.Traditionally, rice and cassava are intercropped with maize, even if commonbeans or a legume cover crop would be more advisable. 2. The density of maizemay be increased up until 10 plants m-2in order to achieve the most productiveresults by using row spacings of 0.5 e 0.9 m, respectively, depending on thegenotypes used. For varieties, with a reduced height such as Perla Pandino, it is possible to use a more narrow row spacing, whilst for tall plants, over 2 m, suchas Cubano Amarillo, a wider row spacing is recommended.