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University of Nairobi (2018)

Contribution of pigeon pea (cajanus cajan l. Millsp.) to soil fertility and productivity of maize (zea mays l.) cropping systems in semi-arid Kenya

Kizito, Musundi K

Titre : Contribution of pigeon pea (cajanus cajan l. Millsp.) to soil fertility and productivity of maize (zea mays l.) cropping systems in semi-arid Kenya

Auteur : Kizito, Musundi K

Université de soutenance : University of Nairobi

Grade : Doctor of Philosophy (PhD) in Soil Science 2018

Résumé partiel
Pigeonpea breeding programs in Kenya have focused mainly on developing high yielding varieties that are resistant to Fusarium wilt and adaptable to a broad range of ecological conditions. However, few studies have evaluated these pigeonpea varieties for soil fertility improvement and contribution to the productivity and sustainability of maize-based cropping systems under a changing climate. A study comprising field and greenhouse experiments was conducted between 2009 and 2013 to : (i) quantify the amount of nitrogen fixed by improved pigeonpea varieties under maize-pigeonpea intercropping systems, (ii) determine the amount of nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg) and calcium (Ca) accumulated by the different components of maize-pigeonpea intercropping systems and its effect on total soil N, available P and exchangeable K, Mg and Ca content, (iii) determine the effect of pigeonpea and maize residues on soil aggregation and soil water content, and (iv) predict the impact of climate change on maize and pigeonpea yields. Field experiments were conducted in Katumani Research Centre using a split-split plot design with three pigeonpea varieties, two cropping systems and three crop residue regimes as the main plot, sub-plot, and sub-sub-plot, respectively. Greenhouse experiments were conducted at Muguga Research Centre where five pigeonpea varieties were screened for biological nitrogen fixation (BNF) and response to Rhizobia inoculation in plastic pots filled with 10 kg of soil and replicated four times in a completely randomized design. Agricultural Production Systems Simulator (APSIM) model version 7.3 was used to predict the impact of climate change on maize and pigeonpea yields. Data collected on total soil N and organic carbon (C), available P, exchangeable K, Mg and Ca, N-uptake, BNF, soil water content, aggregate stability, bulk density and maize and pigeonpea yields were subjected to analysis of variance using GENSTAT statistical software version 14.2. Results showed that all the three pigeonpea varieties fixed 60–70 kgN ha-1, meaning they were all good nitrogen-fixers. However, Mbaazi II fixed significantly (p ≤ 0.05) higher N (70 kg N ha-1) compared to KAT 60/8 (66 kg N ha-1) and Mbaazi I (62 kg N ha-1) when intercropped with maize. Pigeonpea had significantly (p ≤ 0.05) higher N uptake compared to maize ; Mbaazi II (84-114 kg N ha-1) absorbed more N followed by Kat 60/8 (29-44 kg N ha-1) and Mbaazi I (20-37 kg N ha-1). Intercropping maize with pigeonpea reduced (p ≤ 0.05) soil organic carbon and total soil N from 1.4 and 0.2% in 2009 to less than 1 and 0.1%, respectively, in 2013. Intercropping maize with long duration pigeonpea (Mbaazi II) and ploughing back 4 t ha-1 of crop residues had no significant effect on available P. However, it increased (p ≤ 0.05) available P from 26 ppm at the start of the study to 50 ppm and 47 ppm in eight seasons under maize-Mbaazi I and maize-Kat 60/8 intercrops, respectively.

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Page publiée le 15 novembre 2018