Intensive tillage effects on spatial variability of soil test, plant growth, and nutrient uptake measurements.

摘要

Spatial variability and positional similarities between soil chemical and plant properties were examined and sample size requirements for assessing these relationships determined on a silt loam (Aquic Hapludult) in Maryland, USA. Tillage-related operations are provided in the accompanying manuscript. Rye was planted in October 1987. Samples were taken at 1-m intervals in April 1988 along two parallel 45-m transects in the East-West direction and two parallel 37-m transects in the North-South direction. Plant tissue was hand-clipped from an area of 0.1 m2 and subsequently analysed for biomass, plant N, P, and K. Disturbed soil samples were taken from the 0-15 cm depth and analysed for soil NO3-N, P, K, Ca, Mg, pH, and organic matter (OM). Plant tissue macronutrients exhibited minimal differences in the coefficients of variation (CV) with values near 25%. Soil N, P, K, and Ca generally showed similar CV values of 15 to 20%. Magnesium, pH, and OM concentrations generally exhibited CVs of <10%. PlantN and P exhibited strong spatial dependence, whereas biomass and plant K exhibited moderate spatial dependence. With the exception of P and Ca, all soil chemical properties exhibited moderate spatial dependence. There were few positional similarities between biomass production and plant macronutrient concentrations. Biomass exhibited strong positional similarities with soil NO3-N and pH, whereas soil NO3-N and plant N indicated positional similarities with increasing values. Soil OM and NO3-N had similar patterns for high measured values. Soil and plant P exhibited strong positional similarities, but this was not true for soil K or plant K uptake, indicating other factors may be involved. After intensive tillage, the sample size requirements were lower for soil properties than for plant properties. It is inappropriate to make recommendations on equal sample size for plant and soil properties unless the properties exhibit the same degree of variability.