Meteorological and agronomic factors in the growth of sugar beet

Abstract

A neutron moderation meter was used to measure soil moisture to depths of up to 1 m in plots of sugar beet grown at three plant populations (100,000, 130,000 and 300,000 plants/ha), with limited irrigation and without irrigation. Recording began in October 1980 and continued until May 1981. From these measurements, the actual evapotranspiration was calculated. These estimations were compared with Energy balance/Bowen ratio measurements of evapotranspiration on a selected day. The Penman method was used to calculate the potential evapotranspiration.

The total amount of water used (evaporation plus transpiration), on average from soil reserves and rainfall was about 460 to 533 mm without irrigation and with limited irrigation respectively. The water use efficiency was 33.3 - 41.7 kg ha⁻¹ mm⁻¹ by the higher and lowerplant population respectively.

A simple exponential equation was used to estimate the absorbed radiation. The values of crop growth rate (CGR) were closely related to radiation absorbed. About 2.0 g of dry matter (DM) and 1.3 g of sugar yield produced by each MJ of photosynthetically active radiation (PAR) absorbed, equivalent to a growth efficiency (Єg) of approximately 3.1% and 3.9% for high populations and low population respectively.

The estimation of water use and radiation utilization were potentially useful for determining the likely effects of weather including the agronomic management (plant population, irrigation) on the growth and yield of sugar beet and irrigation practices in Canterbury conditions.