Section 3 (Crop Management)

Maize-rice rotation in Thailand
On-farm test of nitrogen fertilization for maize grown after rice
A study consisted of two experiments was conducted at PSL FCES followed by an on-farm test
during the dry season of 1998/1999. A split plot in RCB design with four replications was used in the first
experiment. Maize cv. NS 72 was planted under different nitrogen fertilizers in terms of timing and its
amounts of application. The following experiment was conducted at the various farmers’ field and was
separatedinto two plots namely 50 kg N ha -1 applied as a top-dressing fertilizer (30 days after planting)
and 120 kg N ha -1 splitted into basal and top-dressing fertilizers. In the first experiment, data was
analyzed the same as in experimental 3. The Student t-test and marginal rate of return (MRR) was also
used to compare in the second experiment.
Results and Discussion
Maize after rice as compared to the second rice
Maize and second rice grown well during a dry season due to adequate water consumption and
fertilizer application. As displayed in Table 1, the costs of production in maize and second rice were
found to be similar i.e. 13,125 baht ha -1 for maize and 13,750 baht ha -1 for rice, respectively.
Benchaphun et al. (2001) reported that more than 80 % of the costs in maize production was variable
costs, 50 % being labor costs and 30 % was material costs. In addition, labor costs were composed of
mostly land preparation and harvesting costs. In terms of material costs, the largest item was fertilizer cost
and seed costs. However, maize produced 18 % of kernel yield greater than those of the second rice.
Maize also gave 36 % of incomes and 141 % of profits better than the second rice.
Limits to productivity
Crop yields were generally lower in intercrops. Since most crops, particularly maize, were developed
as monocrops, there was a need to develop variety and management techniques to increase the
productivity of maize in rice-based cropping system. From the experience of the authors, the experiment
station yield for maize grown under post-rice condition was 10 ton ha -1 , researcher’ s yield in farmers’
fields was 7.5 ton ha -1 , and farmers’ yield was only 5 ton ha -1 . Pandey (1986) suggested that the gap
between experiment station yield and researchers' yield in farmers’ fields was caused by environment and
soil factors, and the gap between researchers' and farmers’ yields was due to technical resources and
social factors.
The reasons for yield differences between potential and farmers’ average yield levels could be
summarized as follows:
1. lack of suitable maize varieties for post-rice condition;
2. seeds not readily available to farmers during dry season;
3. poor stand, causing lack of quality seeds;
4. delay planting time due to delay the staple crop ;
5. poor water drainage resulting from poor soil management, causing heavy-soils textured ;
6. poor water distribution resulting from poor water management, causing water logging and
moisture stress;
7. poor N fertilizer management resulting from amounts and timing of application.
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