Effects of manure and fertilizer on maize at a research station and in a smallholder (peasant) area of Zimbabwe

The use of manure and fertilizer to increase maize yield is a common practice in the smallholder-farming sector of Zimbabwe. In this study the effects of manure and fertilizer on maize growth, yield, and nutrient uptake were evaluated at Grasslands Research Station and at Matiza in Chihota communal area from 1983/84 to 1988/89 as a part of a wider project on sandveld soils in Zimbabwe. Comparisons were made between 15 t ha− 1 of manure applied biannually and annual applications of 150 and 300 kg ha− 1 of Compound D (8% N, 14% P2O5, 7% K2O, and 6.5% S) fertilizer. Feedlot manure applied at Grasslands increased grain yield by a seasonal average of 16% compared with 8–9% for the fertilizer additions; the residual effects of manure being about the same as the direct effects. At Matiza, three direct applications of smallholder area manure resulted in a mean yield increment of 59% while the fertilizer treatments enhanced yield by 34–63%; but there was little residual effect (10%) of manure. Increase in nutrient contents of young plants and cob-leaves due to manuring at Grasslands indicated that the three feedlot manures applied, which had nitrogen:phosphorus:potassium (NPK) ratios of 5:1:3, 4:1:4 and 5:1:2 acted primarily as NPK fertilizers between 1984/85 and 1988/89. In the late growth stages, such as at tasseling, these manures were also good sources of magnesium (Mg). The smallholder area manures applied at Matiza acted principally as K fertilizers when NPK ratios were 7:1:7 (1983/84 to 1994/85) and 11:1:9 (1987/88 to 1988/89), but acted as NPK fertilizers when NPK ratio was 4:1:4 (1985/86). Feedlot manure was effective in correcting deficient or low N, P, or Mg status at Grasslands, but both manure and fertilizer did not effectively influence the assessed poor status of these nutrients at Matiza. Low NPK ratios of feedlot manures indicated greater potential for correcting the imbalance of P relative to N and K. Over the six seasons, increments in grain yield were in the order of 15 t ha− 1 manure >300 kg ha− 1 = 150 kg ha− 1 fertilizer at Grasslands and 300 kg ha− 1>150 kg ha− 1 and 15 t ha− 1 at Matiza. The results reported here were originally submitted to a local journal, which became defunct before publishing these data.