Abstract

Maize (Zea mays L.) is a staple food crop in Malawi, with average yields of 1.8 -2.2 t ha-1 compared to potential yields of 5 to 10 t ha-1. In some areas, soil acidity is a serious constraint in crop production. The current recommendation is to apply 2.0 t ha-1 of lime as pre-plant broadcast and incorporated into soils with pHW < 5.5. A pilot study was conducted during 2015/2016 season at Bunda Campus (14° 35 S’;  33° 50 E’) to evaluate the response of reduced lime application rates of 0, 100, 250 and 500 kg ha-1 applied by  point placement or dollop method (mirodosing) in comparison to recommendation pre-plant broadcast application. A uniform fertilizer application of 69:23:0+4S was made on all plots. Gross Margin (GM) analysis, Value Cost Ratio (VCR) and Benefit-Cost Ratio (BCR) were undertaken. A gross Margin analysis was done using prevailing input/out values of 2019 at exchange rate of Malawi Kwacha, MK 745 = 1USD. Results showed that the ‘no lime’ control (4.01 t ha-1) gave the lowest grain yield and was significantly (P<0.05) out-yielded by the rest of the treatments. The highest yield of 5.75 t ha-1 was observed from the 500 kg ha-1 application, while the recommended control of 2t/ha yielded 4.90 t ha-1. The BCR was >1.0 for all treatments at two price scenarios of US$0.201 kg-1 and US$0.268 kg-1 grain, but >2.0 only for 100, 250 and 500 kg ha-1 lime application rates. VCR ranged from 4.4 to 10.4, except for 2 t ha-1 treatment which had 0.78 and 1.05 at US$0.201 and US$0.268 kg-1 grain price, respectively.  The results demonstrated that there is potential in reduced lime application rates to increase yield of maize by microdosing of agricultural lime. This study has provided a solid basis for wider evaluation of the concepts for subsequent rolling out to famers.

Key words: Dolomitic lime, soil acidity, microdose applications, aglime profitability.