Growing Rice, Sorghum and Wheat

11. Rice: a crop of the marshlands

Rice needs warm weather and standing water, so in Rwanda it is grown in marshlands developed with bunds (low earth walls), canals and gates that let farmers fill and drain each plot. Clay or clay-loam soils are best, because they hold water.

1. Land preparation. Repair bunds and clean canals. Flood the plot, then hoe or plough it and puddle it to soft mud. Level it with a board or rake, so the water stands at the same depth everywhere: high spots grow weeds, low spots drown seedlings.
2. Nursery. Soak certified seed in water for about 24 hours, then keep it moist and covered for 24 to 48 hours until the first white tips show (pre-germination). Sow it thinly on a raised, wet, well-manured bed near a water supply.
3. Transplanting. Seedlings are ready at about 3 weeks, with 4 to 5 leaves. Lift them gently with the soil still wet, and plant 2 to 3 seedlings per hill, 2 to 3 cm deep, in straight lines, commonly 20 cm by 20 cm. A rope marked every 20 cm keeps the lines straight, so a rotary weeder can be pushed between them later. Old seedlings tiller poorly; plant within the day they are lifted.
4. Water management follows the stages of growth (Figure 4). The crop needs most water from panicle initiation to flowering: a dry spell then causes empty grains.
5. Fertiliser. A basal fertiliser such as NPK is mixed into the mud at the last levelling. Urea is top-dressed in two splits: at active tillering and at panicle initiation, onto shallow water so it is not washed out of the plot.
6. Weeding: two or three times, by hand or with a rotary weeder between the lines, before the canopy closes.
7. Pests and diseases: birds eat grain from the milk stage, so the crop must be guarded until harvest. Rice blast, a fungal disease, makes diamond-shaped grey spots with brown edges on leaves and can rot the neck of the panicle. Rice yellow mottle virus makes leaves yellow and plants stunted. Use resistant varieties, clean seed and balanced fertiliser, and avoid too much nitrogen, which encourages blast.
8. Harvest when about 80 to 85% of the grains on the panicles are straw-coloured. Cut the crop, thresh it on a tarpaulin (never on bare soil, which adds stones that break mills), winnow it and dry the paddy to about 14% moisture before storage or sale.

Figure 4. Typical water depth in a transplanted rice plot. Follow the advice for your marshland: depths and dates vary with the variety and the season.

22. Sorghum: drought tolerance, birds and witchweed

Sorghum survives dry spells better than maize: its roots go deeper, its leaves have a waxy coat, and the plant can stop growing in drought and start again when rain returns. That is why it suits the drier east and the less reliable Season B.

1. Land preparation: a fine, firm seedbed, because the seed is small.
2. Sowing: drill the seed thinly along rows 60 to 75 cm apart, 2 to 3 cm deep (about 8 to 10 kg ha⁻¹). Broadcasting, still common, wastes seed and makes weeding hard.
3. Thinning at 2 to 3 weeks, leaving one strong plant every 15 to 20 cm. Thinnings can be fed to livestock.
4. Weeding twice, at about 2 and 5 weeks after emergence.
5. Striga (witchweed). Striga is a parasitic weed: its roots attach to the roots of sorghum, maize or millet and draw water and food from them, so the crop is stunted and yellow before the weed even appears above ground. Control: pull Striga by hand before it flowers (one plant sheds thousands of tiny seeds), rotate with legumes, add manure, and use tolerant varieties.
6. Birds such as weavers and queleas eat sorghum grain from the milk stage. Sow at the same time as neighbours, so damage is shared; scare birds from dawn to dusk during grain filling; or grow brown, high-tannin varieties, which birds find bitter.
7. Harvest when the grain is hard and cannot be dented with a fingernail. Cut the heads, dry them on a tarpaulin, thresh by beating, winnow, and dry the grain to about 12 to 13% moisture. The stalks are used as fodder, fuel or fencing.

33. Wheat: a crop of the cool highlands

Wheat needs cool weather, so in Rwanda it is grown on the high ground of the north, west and south-west, mostly in Season B.

1. Land preparation: a fine, level, weed-free seedbed.
2. Sowing: drill seed in rows 20 to 25 cm apart, 3 to 5 cm deep, or broadcast it evenly and rake it in. Plants are far too many to count, so the farmer works with a seed rate, typically 100 to 125 kg ha⁻¹ when drilled (Worked example 2 shows where such a figure comes from).
3. Fertiliser: a phosphorus fertiliser such as DAP at sowing, and urea at tillering.
4. Weeding once or twice in the first 4 to 6 weeks, before the crop covers the ground.
5. Diseases: the rusts (yellow or stripe rust, stem rust and leaf rust) are fungi that cover leaves and stems with orange, yellow or reddish-brown powdery pustules, and can wipe out a crop. Grow resistant varieties from certified seed, and plant on time.
6. Harvest when the straw is golden and the grain is hard. Cut with a sickle, tie in sheaves, thresh, winnow and dry the grain to about 12 to 13% moisture.