Effect of Legume Cover Crop on Sweet Orange (Citrus sinensis) Fruit Weight and Brix

Recent reports show that orange yield and fruit quality is on the decline in Kenya’s coastal lowlands
hence need for an efficient and sustainable production system. A field study was conducted in
Vitengeni, Ganda and Matuga locations within the coastal lowland of Kenya from May 2012 to April
2015 to evaluate the effect of three legume cover crops on orange fruit weight and brix. The
treatments included mucuna (Mucuna pruriens), dolichos (Lablab purpureus), cowpea (Vigna
unguiculata) cover crops and fallow of natural vegetation as the control. The experiment was laid out
in a randomised complete block design (RCBD) and each treatment replicated four times within the
four blocks. Data collected were orange fruit weight, orange fruit brix, weather, soil texture and
composition. The data was subjected to the analysis of variance (ANOVA) using the procedures of R
statistical analysis software version 3.3.2 (R Core team, 2015). Mean separation was done using the
least significant difference (LSD) at 5% level of significance. The results from the study showed that
mucuna, dolichos and cowpea significantly (P=.05) increased fruit weight and brix. There was
interaction effect between treatments and sites. Mucuna increased orange fruit weight by 12.4%,
10.5% and 7.6% for Ganda, Matuga and Vitengeni respectively. Orange fruit weight increased by
8.8%, 7.8% and 7.2% for Ganda, Matuga and Vitengeni respectively due to dolichos and 6.0% for
Ganda due to cowpea. Orange fruit brix increased by 5.8%, 5.1% and 4.2% for Vitengeni, Matuga and
Ganda respectively due to mucuna. Cowpea increased orange fruit brix by 4.6%, 3.8% and 3.2% for
Vitengeni, Matuga and Ganda respectively. Orange fruit brix increased by 3.3% and 3.1% for
Vitengeni and Matuga respectively due to dolichos. From the outcome of this study, mucuna is
recommended for use in orange tree orchards as it is useful in improving yield and fruit quality.