Responses of maize grain yield to changes in acid soil characteristics after soil amendments

Abstract

An experiment was conducted from 1997 to 2000 on an acid soil in Cameroon to assess the effectiveness of cultivating acid tolerant maize (Zea mays L.) cultivar and the use of organic and inorganic fertilizers as options for the management of soil acidity. The factors investigated were: phosphorus (0 and 60 kg ha−1), dolomitic lime (0 and 2 t ha−1), organic manure (no manure, 4 t ha−1 poultry manure, and 4 t ha−1 of leaves of Senna spectabilis), and maize cultivars (ATP-SR-Y – an acid soil-tolerant, and Tuxpeno sequia – an acid susceptible). On acid soil, maize grain yield of ATP-SR-Y was 61% higher than the grain yield of Tuxpeno sequia. Continuous maize cultivation on acid soil further increased soil acidity, which was manifested by a decrease in pH (0.23 unit), exchangeable Ca (31%) and Mg (36%) and by an increase in exchangeable Al (20%). Yearly application of 60 kg ha−1 of P for 3 years increased soil acidity through increases in exchangeable Al (8%) and H (16%) and a decrease in exchangeable Ca (30%), Mg (11%) and pH (0.07 unit). Lime application increased grain yield of the tolerant (82%) and susceptible (208%) cultivars. The grain yield increases were associated with a mean decrease of 43% in exchangeable Al, and 51% in H, a mean increase of 0.27 unit in pH, 5% in CEC, 154% in exchangeable Ca, and 481% in Mg contents of the soil. Poultry manure was more efficient than leaves of Senna producing 38% higher grain yield. This yield was associated with increases in pH, Ca, Mg and P, and a decrease in Al. The highest mean grain yields were obtained with lime added to poultry manure (4.70 t ha−1) or leaves of Senna (4.72 t ha−1). Grain yield increase was more related to the decrease in exchangeable Al (r = −0.86 to −0.95, P<0.01) and increase in Ca (r = 0.78–0.94, P<0.01), than to pH (r = −0.57 (non-significant) to −0.58 (P<0.05)). Exchangeable Al was the main factor determining pH (r = −0.88 to −0.92, P<0.01). The yield advantage of the acid tolerant cultivar was evident even after correcting for soil acidity. Acid soil-tolerant cultivars are capable of bringing unproductive acid soils into cultivation on the short run. The integration of soil amendments together with acid soil-tolerant cultivar offers a sustainable and comprehensive strategy for the management of acid soils in the tropics.