Three separate experiments were conducted at Experimental Farm, Horticulture Department,
Faculty of Agriculture, Moshtohor, Benha Univ., Egypt at 2014 and 2015 seasons. The aim of this
study was to evaluate some intercropping systems of corn, soybean and cowpea with Washington
navel orange at different N fertilizer levels versus solid ones. Soil fertility, weed control, competitive
relationships and biological & economic evaluations of the intercropping system were considered in
the study. Experimental design was RCBD with three replicates. The treatments of each experiment
were including intercropped one of the three corn, soybean or cowpea with Washington navel orange
orchards at four levels of nitrogen fertilization (0, 25, 50 and 75%) of the recommended fertilizer
level of corn, soybean or cowpea as well solid culture of each crop. The obtained results from three
trials revealed that intercropping legume crops with Washington navel orange trees increased
available NPK (mg kg-1) content in soil trees as well as more effective in suppress weeds. Superiority
of fruit yield and quality of monoculture over intercropped orange orchards were detected. But
statistical analysis indicated that orange orchards with legumes as intercrop (soybean or cowpea) at
50 and 75% of N levels produced significantly higher fruit yield and enhanced fruit quality traits
compared with monoculture of orange tree. Intercropping three secondary crops under orange tree
was significantly decreased crop growth rate (CGR), light intensity %, yield and yield components
over than monoculture. Increasing levels of N fertilization from 0 up to 75% significantly increased
and enhanced all studied traits for main and secondary crops, except light intensity %. The highest
values of nitrogen use efficiency (NUE) were achieved at 75% N fertilization in corn and soybean,
but at 50% N levels in cowpea. All intercropping treatments increased total productivity of unity area,
except unfertilized corn/orange intercropping system as well orange trees was dominant and had
higher competition ratio than corn, soybean or cowpea. Polyculture of orange orchards is a successful
technology to increase land equivalent ratio (LER), land equivalent coefficient (LEC), total cereal
units (CUs), total return as well as monetary advantage index (MAI). The increases in total return
were 9.05, 18.96 and 19.84% at 75% N level over solid orange, while MAI values were L.E. 6346,
7959 and 9652 in orange orchard intercropped with corn, soybean and cowpea, respectively, as average of both seasons. |
