The donkey as a draught power resource in smallholder farming in semi-aridwestern Zimbabwe 2. Performance compared with that of cattle when ploughing on different soil types using two plough types

The work performance of two teams of four donkeys (heavy, 680 kg and light, 460 kg) and one pair of Jersey crossbred oxen (646 kg) was compared when t hey ploughed 4 h/day on four types of soil (clay, redsoil, sandy soil and s andy clay) using two types of plough, a conventional ox plough (40 kg) and a lighter prototype, the 'Walco' plough (32 kg) on an experimental farm. Wo rk parameters were also measured with farmers' cattle and donkey teams plou ghing on farms in Matobo and Nkayi districts. Working speed, power and effe ctive field capacity (EFC) were higher for the ox-team (1.03 m/s, 920 W and 14.5 h/ha for the conventional plough and 0.99 m/s, 745 W and 13.9 h/ha fo r the Walco plough) and the heavier donkey team (0.87 m/s, 689 W and 14.2 h /ha for the conventional plough and 0.87 m/s, 787 Wand 17.3 h/ha for the Wa lco plough) than for the lighter donkey team (0.59 m/s, 461 W and 22.1 h/ha for the conventional plough and 0.64 m/s, 445 Wand 23.4 h/ha for the Walco plough). Expressed as a proportion of live weight or metabolic live weight there were no significant differences in draught forces exerted between te ams but power output per unit live weight was greater in the ox-team than i n the light donkey team but similar to that in the heavy donkey team. The W alco plough required a lower force (742 N) to operate than the conventional plough (826 N) but apart from this did not have any marked advantages over the conventional plough. On-farm, team sizes of donkeys varied from three to seven animals (team weight 340 kg to 1007 kg) and cattle team sizes from two to four animals (team weights 558 to 1709 kg). Regardless of team numb er, the heavier teams tended to out-perform the lighter teams (speed range 0.63 to 1.08 mis, power 395 to 1136 W, EFC 9.1 to 25 h/ha)) with one except ion, a well trained team of two oxen (team weight 879 kg, speed 1.02 mis, p ower 775 W, EFC 9.1 h/ha). Donkeys tended to plough at a slower pace than o xen, with a lower power output, although when weight differences between te ams were equalized (four heavy donkeys compared with two oxen), then there was little to chose between the species. Results suggested that teams of th ree or more donkeys can effectively be used for ploughing on the soils test ed. The results highlighted the importance that team live weight and traini ng/experience have in determining work performance.