Effect of Intra-Row Spacing of Cowpea (Vigna ungucilata L.Walp.) Grown Under Rain-fed Conditions on Growth Attributes, Forage and Seed Yield in South Darfur State, Sudan

Abstract

A field trial was conducted on a farmer’s field near the village of Ori Jamaliy, Abga Ragil Administrative Unit, Belail Locality, around 7 kilometers to the south of Nyala city, South Darfur State, Sudan. The area lies in the low rainfall savanna belt of Sudan. The trial lasted for three seasons: 2013/14, 2014/15 and 2015/16. The purpose of the study was to investigate the effect of inter-row spacing on cowpea productivity and other growth attributes. The experimental design included four intra-row spacing's: 50, 75, 100 and 125 cm while inter-row spacing was 100cm.The parameters that were studied included plant growth, plant density, vegetation coverage, plant length, survival rate, dry matter production at flowering and at maturity, number and weight of bacterial nodules at flowering, number of plant pods, pod productivity per unit area, seeds productivity per plant and per unit area; and percentage of moisture in the soil, under rain-fed irrigation circumstances. Data from a complete randomized design with four replications and (8 x 5 m.) plot area were collected through the three seasons. The study showed that, intra-row spacing significantly affected plant density, the highest plant density was recorded at 50 cm and the lowest density was found with intra-row spacing of 125 cm, which were (13 and 4 plants per square meter respectively). Furthermore, there were significant differences due to intra-row spacing in terms of vegetation cover percentage; the greatest plant cover percentage was recorded at intra-row spacing of 50 cm reaching (80.4%) while intra-row spacing of 100 cm resulted in (53.4%). Moreover, plant length was significantly affected by intra-row spacing being (149.2 and 43.2cm) at intra-row spacing of 125 and 50cm respectively. On the other hand, survival rate percentage was not significantly affected though the highest was associated with intra-row spacing of 100cm being (85.4%) while intra-row spacing of 75 cm registered (51.7%). Furthermore, intra-row spacing had not significantly affected forage yield of cowpea, the highest fresh yield was obtained with intra-row spacing of 100 cm being 7.9 t/ha fresh weight or 1.9 t/ha dry matter weight. The lowest fresh yield was obtained with intra-row spacing of 75 cm being 5.6 t/ha equivalent to 1.7 t/ha dry matter. Moreover, the highest pods yield was registered with intra-row spacing of 100cm producing 52.3 pod/m2 and lowest pods yield was 48.3 pods/m2 obtained by intra-row spacing of 75cm. Also, seed production was not significantly affected by intra-row spacing; the 50, 75, 100 and 125 cm spacing produced 117.4, 107.2, 116.8 and 110.4 g/ m2 respectively, which is equivalent to 1.17, 1.07, 1.17 and 1.10 t/ha respectively. IX Nodule number and weight were not significantly different as a result of intra-row spacing, the highest number of nodules/plant was recorded by intra-row spacing of 75cm (71.0 nodules/plant), amounting to 0.47g/plant or (40kg/ha) or 0.04t/ha; while the lowest was recorded by intra-row spacing of 100cm (50 nodules/plant) amounting to 0.53g/plant equal (30kg/ha) or 0.03 t/ha.The study showed that, there were significant differences in percentage of moisture in the soil, the highest soil moisture was found at intra-row spacing of 100cm (7.7%) at a depth of 60cm, the lowest soil moisture percentage was recorded with intra-row spacing of 50 cm at a depth of 20 cm (1.4%). It was concluded that farmers may resort to wider spacing for cowpea forage and seeds production as this involves less cost in terms of seeds and labour under rain-fed conditions in South Darfur state of Western Sudan. This also allows intercropping where farmers can grow anther crop with cowpea which serves as insurance for food security under conditions of climate change