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Eight selected commercial maize hybrids were compared for yield and other performances when grown in irrigated paddy fields under no-tillage and conventional tillage. On-farm trials were conducted on silty clay loam at Phitsanulok Province, Thailand, from November 1998 to April 1999. The no-tillage treatment displayed a 56% higher average grain yield over the conventional tillage treatment. The increased yield was attributed to better moisture conservation and less weed competition. No-till was also superior to the conventional tillage in plant growth and development, as expressed in terms of biomass, kernel numbers and kernel weight.

No-tillage cultivation can be effective not only in increasing soil and water conservation, but also by reducing labour requirements and time (Unger and McCalla, 1980). Maize grown under the no-tillage system usually results in higher yields. Successful results have been reported in Thailand, particularly when applied to rainfed environments (Na Nagara et al., 1984). However, there is very little information available in Thailand about no-tillage systems for maize grown under irrigated conditions in paddy fields.

The objective of this study was to compare yield and other crop performance factors of maize when grown in paddy fields under no-till and conventional tillage systems.

Eight commercial maize hybrids were evaluated under no-tillage and conventional tillage. Two fields were selected, one for no-tillage and the other for conventional tillage. The total area was approximately 1.6 hectares and was divided into eight subplots. Twelve rows of each hybrid were planted in an area of 9 x 200 m in each subplot.

To assure uniform crop emergence, irrigation water was uniformly applied by flooding to the experimental area approximately 30 days after rice was harvested. After the soil moisture was suitable for planting and crop emergence, the conventional tillage plot was plowed once and then harrowed before planting.

On the no-till plot, glyphosate 48% EC (N-(phosphonomethyl) glycine, isopropylamine), a pre-planting herbicide, was sprayed in two split applications at 3 kg of active ingredient per hectare. The first application was applied seven days before planting and the second application was at planting.

Each hybrid in both the no-tillage and the conventional tillage plots was planted at approximately 0.75 x 0.20 meter spacing, with a population objective of 65,625 seeds per hectare. Planting was done with a four-row White-New Idea planter equipped with no-till coulters.

Fertilizer treatments, based on soil test results, were the same on both plots. Lime was broadcast at a rate of 625 kg per hectare immediately after the pre-planting irrigation. DAP (18-46-0) and KCL (0-0-60) fertilizers were mixed and applied at a rate of 187.5 kg per hectare and 125 kg per hectare, respectively. Urea (45-0-0) was also applied at 188 kg per hectare, with top-dressing done by hand at 30 days after planting and again at flowering.

In the conventional tillage plot, weeds were controlled with metolachlor (40% EC) at 1.5 kg of active ingredient per hectare followed by one cultivation at 30 days after planting. There was no more weed control after planting on the no-till plot. Carbosulfan or furadan were used for insect pest control on both plots.

The conventional tillage plot was irrigated three times in addition to the pre-planting irrigation. The no-till plot was irrigated only two times in addition to the pre-planting irrigation. Both plots also received 19.3 mm of rainfall during the late growing season.

As shown in Table 1, plant growth factors, except for plant height, were superior in the no-till plot. No-till treatments showed an average of 15% higher volume of biomass over the conventional tillage.

The results in Table 1 also indicate significantly greater water storage in the top 0.2 m of soil surface after one month in the no-till plot as compared to the conventional tillage plot. Better weed control, as indicated in Table 1 by weed dry weight, is also associated with the no-till practice.

Kernel numbers and kernel weight were the most important traits of yield components in this trial. As displayed in Table 2, the no-till plot produced an average of 12% more kernels per ear and 5% greater weight per 100 seeds than the conventional tillage plot. There were also significant differences between the two plots in terms of days to 50% silking and shelling percentage (Table 1). However, there was no significant difference in ear number and plant population between the two plots (Table 2).

As shown in Table 2, the no-till plot produced an average of 56% greater grain yield than the conventional tillage plot. This superior yield is attributed mainly to greater soil moisture conservation and less weed competition.

These results indicate that the yield of maize following rice may be improved by using no-till practices. The increase in yield under the no-till system results from conservation of soil water and reduction of weed competition. No-till could be applied in areas with limited irrigation water, as well as rainfed environments, when weeds can be effectively controlled using pre-planting herbicides. More research is needed, however, to determine the effectiveness of no-till practices in areas of low fertility and coarse textured soils.

Na Nagara, T., C. Tongyai, D. Ngovathana, and S. Nualla-ong. 1984. No-tillage for corn. Thailand National Corn and Sorghum Program Annual Report. pp.186-200.

Unger, P.W., and T.W. McCalla. 1981. Conservation tillage systems. Advances in Agronomy. 33:1-58.

Table 1 Some agronomic characters of maize hybrids grown under different

tillage practices at Phitsanulok Field Crop Exp. Station during 1998-1999.

Table 2 Mean grain yield at 15% moisture content and yield components of maize