Studies on the availability to plants of soil nitrogen in Malaysian tropical oligotrophic peat. III–Effects of initial soil air-drying and frequency of watering
AbstractPartial air-drying of peat from 90 per cent (v/v) moisture (pF 0·4) to 15 per cent moisture (pF 4·5) and remoistening to 67·5 and 45 per cent moisture (pF 1·9 and 3·3), with subsequent alternate daily watering (38 mm/week), generally reduced the number of leaves plant height, dry matter (DM) production and uptake of Napier grass (Pennisetum purpureum) at the last three of five harvests. Root DM and uptake was similarly reduced. At the first harvest, 67·5 per cent moisture had given the highest DM production and uptake probably because of an initial high rate of mineralization following remoistening. The failure of this treatment to maintain its standing was attributed to moisture loss by evapotranspiration coupled, consequently, with the inability of the peat to retain moisture on becoming irreversibly dry. In a second experiment in which 38 mm of water per week was applied to undried peat at three frequencies, watering daily and on every fourth day generally increased tillering, number of leaves, plant height, DM production and N uptake compared with weekly watering, as more frequent watering probably gave more frequent flushes of N mineralization. No significant difference was observed between watering daily and on every fourth day. The implications of the findings to tropical peat soil management are discussed.