Results Obtained during the Final Year of the Sugar Beet Project in Natal

The results of eleven experiments dealing with (1) lime application, (2) herbicides, (3) nematicides, (4) varieties, (5) fungicides, (6) sowing date and (7) yield potential, are discussed. Lime was necessary, not to create a more neutral soil reaction, but to eliminate most of the exchangeable aluminium in the soil. It was necessary to incorporate lime to a depth of 200 mm but not deeper. Cycloate and ethofumesate applied at 3,7 and 1,O kg ailha respectively allowed the crop to emerge free of weeds. Broadleaf weeds emerged soon afterwards and were controllled with an application of 0,8 kg ailha desmedipham. The efficacy of cycloate depended on the method of incorporation. Nernaticides applied at very high rates prevented a decline iin the plant population due to Meloidogyne incognita but did not prevent serious losses in sucrose yield. Nematodes in clay soils would, for economic reasons, have to be controlled by cultural means. Varieties designated by the breeders as resistant to Cercospora beticola outyielded those that were not even though their resistance was only partial. Cremona, Kawerita' and AM2 Hybrid B were noted as the best varieties for Niital. Triphenyltin acetate (TPTA) was the most effective fungicide used against Cercospora leaf spot while benomyl, which had proved effective in the past, was no longer effective againgt the disease. Fortnightly applications of TPTA from mid-December to the end of March controlled leaf spot almost completely at all sites. Crops grown at commercially acceptable standards yielded 6 to 8 tons sucrose per hectare in April and 10 to 12 tons sucrose per hectare in August and September. Introduction An iinvestigation into the feasibility of growing sugar beet in the Nahl Midlands was conducted over a period of three years. The first year served to identify the main problems involved. The second year was devoted largely to resolving the leaf spot problem. Results of both year's work have been preserlted previouslys* lo* ll. Most of the relevant information now available on sugar beet qroduction in Natal comes from eleven experiments conducted in the final season. These experiments are discussed briefly in order to elucidate the main factors involved in growing sugar beet in Natal. Method Six of the replicated trials to be discussed were conducted on the farm "Lintrose" (1 450 m) at Nottingham Road in the Highland Sourveld and a further three such trials at Baynesfield Estates (880 m) in the Coast Hinterland. A large unreplicated plot of beet was established on the farm "Spring Grove" (1 500 m) near Nottingham Road and another such plot was established on the property of Harden Heights Wattle Co. (1 070 m) in the Midlands Mistbelt. Cultural practices in these two large plots were considered to be commercially practicable. All the experiments were on deep porous clays of the Hutton form. Lime was applied to raise the pH to 5,4 (in water) except where the effect of different levels of lime was to be investigated. All the soils were moderately to highly P-fixing and required large amounts of this nutrient unless P levels were already high. A certain amount of nitrogen mineralization was expected in these soils and nitrogenous fertilizer was applied sparingly (70 to 110 kg N/ha). The amount of P applied ranged from 20 to 100 kg/ha and between 70 and 125 kg of K was applied, according to the results of soil analyses. Seedbeds were prepared with a shallow (50 mm) working of a Lely Roterra or Rotavator and were consolidated by one pass of a Cambridge roller. Drilling was done with a Stanhay precision drill with units mounted 0,5 m apart. Seeds were spaced at 130 mm or more where thinning was to be avoided and at less than 100 mm where thinning was permissible. Thinning of seedlings was permitted only where the ease of crop establishment was not a measure of treatment effects. Results Lime Application (Experiments 1 and 2) The treatments planned for Experiment 1 were four rates of lime and two depths of incorporation. An analysis of soil samples taken after the limestone had been applied showed that the attempt to incorporate to a depth of 400 mm had failed and most of the lime had remained in the top 200 mm TABLE 1 Details of experiments at Lintrose (L), Baynesfield (B), Spring Grove (G) and Harden Heights (IH)