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.  
Highlights
In Malawi, maize (Zea mays L.) is the staple food crop that dominates the cropping systems
A field trial was conducted utilizing a randomized complete block to evaluate seven treatments and four replicates (Table 1); which were designed to compare the recommended application of lime at 2.0 t ha-1 to reduce rates applied as point placements, hereafter referred to as microdosing
Agricultural lime applied at high rates to a large volume of soil has advantage of residual effects which may last for 2-3 seasons
Summary
In Malawi, maize (Zea mays L.) is the staple food crop that dominates the cropping systems. Average yields in the period, 2005 to 2012, ranged between 0.81 and 2.65 t ha-1 (GoM, 2012). Poor soil fertility is one of the major reasons for low yields (Kumwenda et al, 1997; ICRISAT/ MAI, 2000; Blackie and Mann, 2005; MoAFS, 2012).
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