Once a beetroot crop is well established, careful management becomes essential to maximise yield and quality. Proper fertilisation, efficient irrigation and effective pest and disease control play a crucial role in producing marketable roots with good colour, flavour and storage potential. In this second instalment, we look at the management practices that help growers maintain healthy crops throughout the growing season and achieve optimal harvest results.
Fertilising
A soil analysis or test is the most accurate guide to fertiliser requirements. Recommended soil sampling procedures should be followed in order to estimate fertiliser needs, and good management practices are very important if optimum fertiliser responses to beets are to be realised. Top or side dressings of nitrogen should be applied at about 100 kg/ha or (10g/m2) at the three-leaf stage, about three weeks after emergence, and 100 kg/ha three weeks later. Potassium levels should be kept fairly high. The second top dressing can be 1:0:1 or potassium nitrate if K levels are low.
Beetroot prefers welldrained soil, well supplied with lime and potash. Heavy soils usually are not so likely to run short of potash. A lack of phosphorus or nitrogen will stunt growth and produce a deep red colour. When grown extensively under irrigation, beets can tolerate high salt concentrations. Beetroot are sensitive to high acidity and low boron levels. They are, in fact, a good indicator for boron deficiency: blackened areas and cracked roots are usually signs and, when cooked, there are black spots in the tissue and the beets taste bitter.
Irrigating
Always irrigate carefully and, early in the season, take care not to irrigate too much. Waterlogging can turn leaves red and plants may stop growing for a while. As a general guide, apply 300 mm to 350 mm water throughout the growing season, starting off with 20mm in the first week and 40mm every week thereafter.
Irrigation is especially important in the early stages of plant development and during root development. When sowing beetroot, keep the soil damp, lightly irrigating often to keep the surface cool, especially in warm weather. The growth points of emerging seed are very sensitive to hot soil conditions, so during long spells of hot, sunny weather, give 8mm water per day. On cold winter days, about 2 mm of water is needed. It is critical to irrigate the field in the last half of the growing season. Water shortages at this time could have the greatest negative influence on yields. During this period irrigate early in the day so that leaves can dry off and prevent diseases developing.
Harvesting
Soil should be slightly moist before cutting or pulling beets. If the soil is too dry, roots may be difficult to clean and the rate of top breakage may be too high. For best flavour and tenderness, harvesting should begin when roots are 3 — 4cm in diameter. Most beets grown commercially, however, are harvested when they are fully mature to obtain the highest yields. Handle beets carefully after harvesting to avoid damaging the roots. Damage reduces shelf life and increases the chances of decay and disease. Fresh market beets can be stored for 10 — 14 days, at 0°C and 98% to 100% relative humidity.
Also read: Growing beetroot successfully | Establishing a high-yielding crop
Diseases and pests on beetroot
Beetroot is firstly infected with Cercospora leaf spot. Downy mildew Young leaves are thickened, and turn downwards at the edges. A grey fungus growth is visible on the underside of the leaves. The infected parts turn brown later.
Control: The disease is seedborne — use good quality seed. Don’t overwater. Plant in well drained soils.
Control weeds
Don’t plant with too narrow spacing. Root rot, damping-off Germination is poor, the young seedlings grow poorly, turn yellow, wilt, topple over and die. The roots are rotten ad turn black. The disease can be severe on compacted soils.
Control: Don’t overwater. Plant only in soils with good drainage. Treat the seed with thiram. Practice crop rotation. Make sure that the crop does not lack sufficient boron. Plant at the right time and not too deep.
Cutworm
Grey/brown to black worms that feed on the portion of the stem directly above ground level, resulting in toppling over of recently tansplanted young seedlings.
Control: Keep the land free from weeds for about 6 weeks before planting. Apply commercial cutworm bait around seedling stems.
Hawaiian beet webworm
The light greenish larvae of a small brown and white moth feed on the undersides of leaves. They spin loose webbing on the underside of leaves, where they hide and where excreta accumulate. Lesser armyworm. Also known as the beet armyworm. They are usually green, but may be brown or blackish with lengths of approximately 25mm. The larvae hide during the day lower down on the plant betweeen stems or between clods on the ground and emerge at night to feed on the foliage.
Nematodes
Cause swellings (galls) on roots resulting in poor growth of plants.
Control: Crop rotation, intercropping with marigolds, mustard and rapeseed; fallowing; soil solarisation; registered pestcides.
Producing high-quality beetroot requires attention to detail throughout the growing season. Balanced nutrition, adequate moisture and timely pest and disease management help ensure healthy plants and good root development. By combining sound establishment practices with effective crop management, growers can consistently produce a profitable beetroot crop that meets both fresh market and processing requirements.
Source: Agricultural Research Council – Production Guideline for Winter Vegetable Production
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