Browsing by Author "Koech, Mary"
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Publication Effects of nitrogen and phosphorus on shoots and roots biomass of Brachiaria grasses in low fertility soils of North western Kenya(CABI Digitral Library, 2016-09-14) Wairimu, Keziah; Koech, Mary; Mutoko, Morgan; Gichangi, EliasOne of the major constraints to forage production in north western highlands of Kenya, is low soil fertility. The objective of this study was to assess the influence of nitrogen (N) and phosphorus (P) on growth and biomass production of Brachiaria grasses. Seven Brachiaria cultivars: Brachiaria brizantha cvs. Marandu, MG4, Piata, Xaraes, B. decumbens cv. Basilisk, B. hybrid cv. Mulato II and B. humidicola cv. Llanero were compared with two commonly grown forages, Rhodes grass and Napier grass cv. Kakamega 1. The treatments were tested in a split plot arrangement in a randomized complete block design with two rates of NP fertilizer, 0 and 40 kg P ha-1 applied at planting and 50 kg N ha-1 as a seasonal top-dress assigned to the main plot and the grass varieties as subplots. Shoots biomass was determined 14 weeks after seedlings emergence (WAE) and subsequent sampling done after every eight weeks. Roots biomass was assessed from 0-15 and 15 - 30 cm depths at 22, 46 and 80 WAE. During the wet season, the shoots biomass was significantly influenced by NP fertilizer (p = 0.05) and cultivars (p=0.001), but no significant interaction effects occurred. Fertilized grasses yielded 17% more shoots biomass than the unfertilized grasses. Basilisk, Marandu and Xaraes had the highest biomass yields (8.6 – 11.3 t ha-1) and were higher (p = 0.05) than Rhodes grass, and also the other Brachiaria cultivars. Roots biomass was higher at the 0 - 15 cm depth at all sampling times and decreased with depth. Brachiaria cultivars had high roots biomass than Napier and Rhodes grass. Fertilizer response to roots biomass was only noted at 22 WAE only. Basilisk and MG4 are the best Brachiaria options for the north western highlands due to their higher shoots and roots biomass yields.Key words: Dry and wet season, fertilizer, soil quality, shoots biomass.Publication Finger millet response to nitrogen, phosphorus and potassium in Kenya and Uganda(International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)., 2017-06-13) Ndungu-Magiroi, Keziah W.; Kasozi, Angela; Kaizzi, Kayuki C.; Mwangi, Teresa; Koech, Mary; Kibunja, Catherine N.; Wamae, Dixon; Wortmann, C. S.Finger millet (Eleusine coracana (L.) Gaertn) is an important food crop of semi-arid to sub-humid Africa where little is known of its response to applied nutrients. Yield responses to nitrogen (N), phosphorus (P) and potassium (K) together with a diagnostic treatment (S, Mg, Zn, B) were determined from field research conducted in western Kenya and eastern and central Uganda. Grain yield was not affected by applied nutrients in some sites in Kenya, likely due to other prevailing stresses. Grain yield increased with N application for all sites and years in Uganda by a mean of 127% from the no N treatment (0 N) yield of 1.00 Mg ha−1. Grain yield increases ranged from 0.76 to 1.40 Mg ha−1 with 30 kg N ha−1 applied, with little added increase with >60 kg N ha−1. The mean economically optimal rate for N in Uganda was 72 and 43 kg N ha−1 with expected net returns to N of 166 and 279 $ ha−1 when the N cost to grain value was 3 and 9 kg kg−1, respectively. Yield was increased with P and K application at two of four production areas of Uganda. Yield was increased by >20% with application of Mg–S–Zn–B in addition to N–P–K for all sites in Uganda with foliar concentrations indicating possible S and B deficiency. There is great profit potential in Uganda, and less for Kenya for N, but not for P and K, application to finger millet. Response to S and B needs further exploration.Publication Maize-bean intercrop response to nutrient application relative to maize sole crop response(Springer Link, 2017-09-01) Wairimu, Keziah; Wortmann, Charles; Kibunja, Catherine; Senkoro, Catherine; Mwangi, Teresa; Wamae, Dickson; Koech, Mary; Msakyi, JohnMaize-bean intercropping is important in sub-Saharan Africa. Maize sole crop (MSC) nutrient response has been much studied but data is scarce for determination of intercrop functions. A procedure for adapting MSC functions for the maize-bean intercrop was developed. Maize sole crop and intercrop responses were near parallel with notable exceptions for P in high potential areas for maize and for K. Mean intercrop bean yield with no nutrient application was about 0.4 Mg ha⁻¹ and increased on average by 24, 11 and −3% with N, P and K application, respectively. Response function coefficients for MSC adjusted with the ratio of bean to maize grain value as the dependent variable accounted for nearly all variation in intercrop response coefficients providing the basis for determining intercrop response functions from MSC functions. Maize grain yield equivalent was less with MSC compared with intercrop; exceptions were for response to N in high potential areas and for bean to maize value ratios of two or less. The economically optimal rate of N and P were on average about 15% more but less for K with intercrop compared with MSC but with inconsistency. The economically optimal rate ranged widely with variation in the cost of nutrient use relative to grain value but generally without great effect on yield; an exception was a great effect on MSC yield response to N for high potential areas. Intercrop nutrient response functions can be reliably determined once maize sole crop functions are determined for a recommendation domain.