Erosion and soil properties under a banana-corn (Musa sp.-Zea mays) intercropping system with contrasting tillages and hedgerows

Conventional tillage (T1) and interhedgerow cropping treatments whether zone-tilled-unmulched (T2) or zone-tilled-mulched (T3) were tested for their effect on soil erosion, plant growth/yield, weed biomass and soil properties of a silt loam on a 25-40% slope. T2 had a single hedgerow of mahogany (Swietenia macrophylla King.) planted at 2 m spacing while T3 consisted of a 0.5 m Gliricidia hedges (2 rows of Gliricidia sepium planted at 25 cm apart with 50 cm between rows + mahogany within hedgerow) between 10 m alleys where corn and banana (cv lacatan) were grown for two cropping seasons. Gliricidia hedges were pruned every 45-60 days to 50 cm height to provide green manure for the alley crops. Results showed that erosion control, total NPK losses (losses through corn removal and erosion), total porosity, and aggregates with 1-2 mm or less at 0-10 cm soil depth were all greater in T1 than in T2 or T3. Saturated hydraulic conductivity was faster in T1 than in T3 but the opposite was true for the 2 mm aggregates and moisture equivalent. Soil N and moisture content (by January 20, 2001) was greater in T3 than in T1 or T2 whereas soil pH, organic matter, p, K, 15 bar moisture, and available water were similar among treatments. However, the three treatments reduced soil pH significantly after two croppings. T2 also reduced total N in the topsoil while T1 decreased soil moisture at FC [field capacity] and available water significantly. After first cropping, earthworm population and biomass were greater in T3 or T2 than in T1, while earthworm casts were greater in T3 than in T1 or T2. However, weed biomass, was unaffected by the treatments in both cropping seasons. The effect of T3 was better than that of T1 or T2 with respect to final corn height, barren plants, and marketable and total ear yield based on equal harvestable area of sweet corn. However, corn height at various dates, leaf area index, total ear yield (marketable + non-marketable) based on actual harvest area and stover yield of glutinous (lagkitan) and sweet corn were similar among treatments. NPK contents of the stover, ears and husk of glutinous corn were also similar among treatments. In contrast, N and P contents were significantly greater only in the ears of sweet corn under T3 and T1 than under T2. Correlation analysis showed that soil NK, moisture equivalent, and soil moisture during dry season were all significantly correlated with ear yield of sweet corn. Conversely, the stem diameter, leaf number per plant, number of suckers per plant and NPK content of the third youngest leaf of banana as well as the stem diameter and height of mahogany were all unaffected by the treatments. Among the three treatnments evaluated, T3 was the most profitable