Abstract
Field experiments were conducted to study different compaction levels on rice growth. Surface compaction treatments were given at two levels of dry bulk density with the help of steel roller. It was observed that the rice yield was significantly higher at 1.65 Mg m-3 compaction level, compared to the control. However, water use efficiency and cost benefit ratio of surface compaction were increased consid-erably compared to puddled field as the yield was 19% higher at 1..65 Mg ni--3 surface compaction than that from the puddled field.
INTRODUCTION
Rice is grown in puddled fields. Pud-dling reduces the soil infiltration but creates hindrances to the regeneration of soil structure arid impedes root growth. How-ever, puddling is laborious, time consuming and difficult field operation. In country like Pakistan where water is already short, development of alternate method which consumes relatively less water for growing rice is imperative so that the available water supplies are used effectively. The reduction of water infiltration can also be achieved by surface compaction through increased dry bulk density. Ghildyal (1978) reported that the soil compaction up to densities of 1.75 Mg m-3 reduced the water requirement of rice crop considerably as compared with puddling, while the yield increased. Tanaka and Yoshida (1910) noted that puddling and subsequent continuous submergence caused several nutritional disorders such as phos-phorus, potassium, zinc deficiencies, iron toxicity, etc. in tropical Asia. The formation of relatively impermeable layers or plow pans is attributed to physical compaction at
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same depth during puddling (Moormann and Dudal, 1964). Compaction of the soil with a roller has been suggested by Varade and Ghildyal (1967) as the yield of rice grain, total dry matter and roots were posi-tively correlated with soil bulk densities. Varade and Patil (1971) reported that compaction increased rice grain yield over with puddling despite restricted root growth in compacted soil layers. Gupta and Kathawate (1974) observed the highest grain yield of NP-130 and IR-8 rice varieties at compaction levels of 1.82 and 1.72 g cm-3.
