Applying granulated and hydrated hydrophilic polymers at sowing to sustain seedling establishment of spring turnip rape

Abstract

SUM M ARYOptimal temperature and soil moisture conditions for germination of spring turnip rape (Brassica rapa L. subsp. oleifera DC.) are not often realized in Finland. New tools for better establishment, such as water-storing polymers, could ensure a good start for yield formation. Because technologies in field cropping must be cost effective and easy to carry out, the amounts of polymers applied per hectare should be small. After recording non-significant effects of granulated polymers under field conditions and reduced emergence under dry conditions in pots, hydrated polyacrylamide (PAM) was placed under the seeds during drilling, a technique referred to as gel-sowing. Slightly acid PAM polymer hydrated with water was used (5-7 g PAM/kg gel). The gel was pumped directly under the seeds at application rates of 1·0-3·4 kg PAM/ha. The PAM gel did not reduce the need for careful preparation of the soil bed and accurate timing of sowing, but when these prerequisites were fulfilled, the gel sustained early establishment and seedling growth. The gel helped when circumstances after sowing did not favour germination or early establishment. However, accurate placing of PAM gel under the seeds is challenging and further improvements in the technique of gel-sowing could enhance its positive effects.