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Precious Manomano
Herald Reporter
Farmers have been urged to lime acidic soils to improve chances of optimising soil productivity.
This will reverse the acidity of soils and enhance chances of a successful season.
Government has rolled out the Blitz Soil Conditioning Programme to ameliorate soil acidity and improve agricultural productivity.
The programme entails pH analysis and giving lime recommendations.
This information is crucial for informed decision on lime distribution and utilization in the country.
Recently, Cabinet has also approved the Agriculture Recovery Plan whose main objective is to stem the continued reduction in production and productivity of maize, wheat and soya bean.
One of the solid interventions required to reverse the negative production trends, attain self-sufficiency and allow the country to move away from the perpetual importation of these strategic commodities is conditioning the soil in order to improve its productivity.
In a report released by the Department of Research and Specialist services in the ministry of Lands, Agriculture, Fisheries , Water and Rural Development soil acidity is the biggest challenge in most smallholder farms.
It has also become clear that without liming acidic soils, the chances of optimising soil productivity are very slim.
Soil pH is a measure of acidity or alkalinity of a soil and It is measured on a scale from 1-14.
An acidic soil is one whose pH (measured in water) is below 7.0 units while an alkaline soil has a pH above 7.
For crop production, yields are adversely affected when pH is below 5.0 units and soil acidity affects nutrient availability and plant growth.
Incorporation of lime into the soil sweetens it by correcting soil acidity.
Correct soil pH increases fertiliser use efficiency and ultimately improves soil productivity.
Liming a soil beyond optimum pH ranges negatively affects soil productivity.
The report also said more than 70percent of Zimbabwean soils are acidic and require liming to correct pH for optimum crop productivity.
Soil pH variations are largely mediated by amount of rainfall and those areas that receive more rainfall are largely acidic whereas the drier parts of the country are alkaline.
About 65 percent of all the wards in the country have acidic soils that require lime for optimum maize productivity.
”Maize and legumes are important in soil acidity amelioration. The order of acidity (proportion of wards with acidic soils requiring lime) follows the trend: Mashonaland West 66 percent, Mashonaland East 76 percent, Matabeleland North 73 percent, Manicaland 71 percent, Masvingo 67 percent, Matabeleland South 67 percent, Midlands 50 percent, Mashonaland Central 41 percent,” said the department.
The ministry also indicated that soil acidity is a common problem in districts that receive high rainfall such as Chikomba, Seke, Wedza, Marondera, Goromonzi and Murehwa adding that soil acidity correction through liming should be highly promoted.
”Higher soil pH values in more arid districts such as Mudzi and some arid parts of Mutoko district. Problem of lower crop yields could be attributed to low rainfall and not soil acidity in these districts. If rainfall is supplemented by irrigation, such soils would sustain productivity (if adequately fertilised),” said the department.
In Mashonaland central soil acidity is evident in high rainfall districts such as Mazowe, Bindura, Guruve and some parts of Muzarabani, and Mt Darwin.
The report further said soil acidity correction through liming should be highly promoted and having conditioned the soils with lime and balanced soil nutrition through fertilization, these areas will sustain high crop production.
”More arid districts such as Mbire and Rushinga and some arid parts of Muzarabani, Mt Darwin and Shamva districts have higher pH values hence low crop productivity is more attributable to low rainfall and not pH,”said the department.
With supplementary irrigation and good fertiliser regimes, these areas can sustain high crop production.
”Lime is required in those wards which receive high rainfall.
”Highest requirements are in Mazowe district where 80percent of the wards require lime, Bindura 76percent , Guruve 63percent, Muzarabani 45percent, Shamva 41percent, Mount Darwin 28percent, Rushinga 0percent, and Mbire 0percent. Overall, the province has 41percent of the wards in need of lime,” said the department. In Masvingo, Northern districts such as Gutu, Masvingo, Bikita and Zaka are the worst affected by soil acidity.
Gutu district is on the extreme with several wards having strongly acidic soils (pH 4.5 – 4.9) and more arid districts such as Chiredzi, Mwenezi and Chivi) have higher pH values.
Districts which receive highest rainfall have most of the wards that require lime whereas the driest districts such as Chiredzi and Chivi have fewest number of wards that require lime.
”Zaka requires 94 percent of lime , Gutu 88 percent, Bikita 78 percent, Mwenezi 78 percent, Masvingo 77 percent , Chivi 34 percent and Chiredzi 13 percent. For the whole province, 67 percent of the wards require lime,said the department.
In Midlands ,soils in central districts such as Gweru ,Kwekwe and Chirumanzu are mainly acidic.
The northern part of Gokwe North, Gokwe South and southern Shurugwi, Zvishavane and Mberengwa districts have higher pH values.
Gweru and Chirumanzu districts have the highest number of wards that require lime.
The drier districts such as Mberengwa, Shurugwi, Gokwe North and Gokwe South have fewest number of wards that require lime.
Gweru need 95percent, Chirumanzu 92 percent, Kwekwe 70 percent, Zvishavane 63 percent, Shurugwi 42 percent, Gokwe North 28 percent, Mberengwa 27 percent, and Gokwe South 24 percent. Overall, 50 percent of wards in the province require lime.
In Manicaland, Soils in Makoni district are dominantly acidic, all districts have at least 50percent of the soils acidic. This follows the high rainfall belt.
More arid parts of the province have higher pH values northern end of Nyanga, southern end of Mutare, northern parts of Chimanimani and the western border parts of Chipinge bordering Bikita district.
Lime is required in 71 percent of the wards.
In Mashonaland West, most parts of the province are acidic, Makonde, Zvimba, Chegutu and Ngezi districts are predominantly acidic while Sanyati, Kariba and Hurungwe districts have parts that have higher pH values which do not require lime.
Lime requirements of the province is the greatest with 88percent of the wards requiring lime.
All the wards in Chegutu, Zvimba and Makonde districts require lime.
Chegutu need 100percent lime, Zvimba 100 percent, Makonde 100 percent, Ngezi 94 percent, Hurungwe 73 percent, Kariba 67 percent and Sanyati 61 percent.
In Matabeleland North Tsholotsho, Lupane and Nkayi districts are predominantly acidic while Bubi and Umguza districts have parts that have higher pH values which do not require lime.
The driest districts in the province, Hwange and Binga, require the least amount of lime in terms of the proportion of wards that are acidic. The other five districts require more lime with Nkayi 97 percent, Bubi 87 percent, Lupane 82 percent, Tsholotsho 82 percent, Umguza 79 percent, Binga 40 percent and Hwange 35 percent. Overall, the province has 73 percent of the wards requiring lime.
In Matabeleland South, Bulilima, Umzingwane, Insiza and Mangwe districts are predominantly acidic whereas Gwanda and Beitbridge districts have dominance of high pH soils. Mangwe district falls in the middle of these two extremes.
The driest districts, Beitbridge and Gwanda have the lowest number of wards that require lime. The soils are generally alkaline or slightly acidic. However, districts that receive higher rainfall, Insiza, Umzingwane and Bulilima, require more lime. Soils are acidic and would need to be conditioned by lime application.
Tobacco Farmers Union Trust vice president Mr Edward Dune said it is crucial for framers to use line in acidic soils adding that there is a need to scale up awareness programmes to ensure that all farmers have proper knowledge and understanding the importance of soil testing.
He said only 40 percent are applying lime to their soils.
”Because of the artificial fertilisers we use, the soils will end up acidic so we need to neutralise that with lime so that it become alkaline. The most critical time to put lime in our soils is April and May and while our soils are still moist to absorb the lime,” he said
Zimbabwe Farmers Union secretary general, Mr Paul Zakariya said assessment of the nutrient status of the soils are critical in farming.
“The soil needs to be tested for its acidity and alkalinity to determine the right dosage of fertiliser to be applied for improved yields.
He observed that for the country to score improved harvests, the process had to start by fixing the soil health adding that each crop enterprise had its recommended pH levels to influence the effective uptake of nutrients in the soil.
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