Effect of sodium and magnesium fertilisers and irrigation on growth, composition and yield of sugar beet

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Abstract
Field experiments (1968–70) were made to find how sodium and magnesium fertilisers and irrigation affect yield of sugar beet. 0 and 250 kg/ha sodium (as agricultural salt) and 0 and 100 kg/ha magnesium (as kieserite) were tested; also no water and irrigation, to prevent the calculated soil moisture deficit from exceeding 40 mm. The plants contained most sodium during August when plants not given it contained 80 kg/ha and plants given it contained 145 kg/ha. Measured losses of sodium and potassium from the soil equalled the total taken up by the crop. Sodium and irrigation increased the leaf area index and total dry matter of the crop. The average increase in sugar yield was 0·5 t/ha from sodium and 0·68 t/ha from irrigation. From late July onwards, irrigated plants had slightly fewer leaves than unirrigated ones. Plants given sodium had more of their total dry matter in the roots than those not given sodium. The effects of sodium and irrigation were additive. Magnesium fertiliser increased the concentration of magnesium in the plants and their total content, but had no effect on growth, uptake of the other cations or final yield of the crop. It is concluded that sodium increased sugar yield by increasing the leaf area index early in the season and by increasing the proportion of the total dry matter partitioned to the roots; irrigation also appeared to act partly by increasing leaf area index but it also greatly increased the uptake of nutrients.