Yields and protein content of two cowpea varieties grown under different production practices in Limpopo province, South Africa

A three-factorial field experiment was carried out at the University of Limpopo experimental Research farm during two planting seasons (2005/06 and 2006/07) to examine the effect of cowpea-leaf removal on cowpea performance. Three treatment factors namely cowpea varieties (Pan 311 and Red Caloona), cropping systems (sole and intercropping) and cowpea-leaf pruning regimes (pruned and un-pruned) were combined and arranged in a randomized complete block design (RCBD). Sole cowpea and sweet corn treatments were included and all treatments replicated four times. Fully expanded cowpea leaves on all cowpea plants in the two middle rows were harvested once at seven weeks after seed sowing prior to flowering. Growth and yield component data were collected from component crops while the protein content of harvested leaves and green pods as well as those of grains and the fodders at harvest were determined. The results of the study revealed that cowpea leaf protein content ranged from 24.1 to 28.1% and 26.0 to 30.7% for Red Caloona and Pan 311, respectively. The protein content of green cowpea pods obtained from Pan 311 cowpea variety ranged from 18.8 to 25.1% while that of Red Caloona varied between 17.9 and 20.7%. Similarly, the protein content of the fodder obtained after grain harvest varied between 9.3 and 9.4% and 9.9 and 12.3%, respectively for Pan 311 and Red Caloona during the two seasons. The protein content of cowpea grain obtained from intercropped plots (23.7 to 26.3%) was similar to that from sole plots (23.7 to 25.7%). In 2005/06, grain yield was 1704 kg ha-1 and 1480 kg ha-1 respectively for Pan 311 and Red Caloona while 1291 and 512 kg ha-1 were obtained for Pan 311and Red Caloona, respectively in 2006/07. There was a significant season x varietal effects on pod and seed protein content. These results reveal that Pan 311 would be better suited for both vegetable and grain production purposes for human consumption while Red Caloona would better serve as a fodder crop for animal production. The results also show that neither cropping system nor cowpea leaf pruning did have consequential effects on the nutritional value of cowpea plant parts and grains.