Seasonal growth and development of Caucasian and white clovers under irrigated and dryland conditions

Abstract

Dry matter (DM) production of sown monocultures of Caucasian and white clovers was compared under irrigated and dryland (non-irrigated) conditions in their third year. Caucasian clover produced 11.9 t DM/ha when irrigated and 9.4 t DM/ha under dryland conditions, and both treatments exceeded white clover by ~2.5 t DM/ha. This increase in yield reflected ~23 kg DM/ha/day higher production rates in spring and summer. During this period, production rates of irrigated treatments increased by 11 kg DM/ha/day/ºC for Caucasian compared with 8 kg DM/ha/day/ºC for white clover as mean daily air temperature increased from 8-16 ºC. In late summer/autumn, production rates of Caucasian clover decreased more than white clover when air temperature dropped from 16-9 ºC. Growth (photosynthesis) and development (leaf appearance) characteristics of each species were also examined. Leaf photosynthesis was ~6 µmol CO2/m2/s higher for Caucasian than for white clover irrespective of measured air temperatures (7-28 ºC) and soil moisture from 1.00-0.39 of water holding capacity (WHC, 512 mm to 1.5 m depth). Both clovers had similar ranges of optimum temperature (21-25 ºC) and soil moisture (1.00-0.86 of WHC) for photosynthesis. These results could explain the observed higher production rates for Caucasian clover in spring and summer, under both irrigated and dryland conditions. Lower production rates of Caucasian clover in autumn may be attributed to a similar phyllochron (126 ºCd), but higher base temperature (5 ºC) than for white clover (1 ºC), and hence a slower recovery to canopy closure post grazing. This study shows that Caucasian clover has potential to increase spring and summer legume production, in combination or as the sole legume species in both irrigated and dryland grass/clover pastures in lowland temperate environments of New Zealand.