PHOSPHORUS REQUIREMENTS BY MAIZE VARIETIES IN DIFFERENT SOIL TYPES OF WESTERN KENYA

Phosphorus and nitrogen deficiencies limit production of maize (Zea mays L.) in many soils of western Kenya. Considerable amount of work has been done on N nutrition of maize in the region. There is, however, paucity of information on which to base fertiliser P recommendations for increased maize production considering potential differences in responses due to varieties, soil type, and climate. External and internal P requirements, and P utilisation efficiencies of two open pollinated varieties (Ababari and Oking’) and one hybrid (H513) were examined at four P-deficient on-farm sites (2 Ferric Alisol, 1 Haplic Ferralsol, and 1Ferric Acrisol) in western Kenya. The varieties were grown under P fertilisation rates of 13, 26, 39, 52 kg P ha^-1 and a check (no P application). Maize performance varied with site, rate of P application, and variety. The highest grain yields (15% moisture content) at the sites varied from 2,732 to 6,479 kg ha-1 for Ababari, 2,350 to 5,835 kg ha^-1 for H513, and 2,299 to 4,459 kg ha^-1 for Oking’. Internal P requirements ranged from 7 to 24 kg P ha^-1 for Ababari, 4 to 18 kg P ha^-1 for Oking’, and 5 to 18 kg P ha^-1 for H513. Internal P requirements depended on both variety and environment, but more on environment than on variety. Phosphorus physiological efficiency (kg grain kg^-1 P) ranged from 111 to 314 for Ababari, 145 to 277 for Oking’, and 127 to 390 for H513. Ababari performed as well as did H513, and the two were better than Oking’. Ababari is, therefore, recommended for the region since it is open pollinated and, hence, the peasant farmers do not have to buy the seeds every season. Row application of P is inappropriate in case determination of crop external P requirement is required.