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Synopsis Root growth was found to occur in a series of stages which caused roots to appear in different locations of the soil at different times. Root growth stages were associated with stages of top growth.

Replicated field plots on moderately acid sandy loam soils were sampled after 3 to 7 years' annually repeated applications of eight nitrogen sources at rates of 40 to 300 lb N/acre. Soil pH, exchangeable K, Ca and Mg, and lime requirement to pH 6.5 were measured. Acidifying effects to a depth of 15 inches were of the order: (NH4)2SO4 > NH4Cl > NH4NO3 ≊ NH3 ≊ urea > ureaform. Residual basicity from Ca(NO3)2 and NaNO3 was approximately equal to the acidifying potential of climate and management. Observed declines in exchangeable bases were ⅓ to ½ the calculated equivalent acidity of acidifying carriers; increases in lime requirement were 1.5 to 6 times greater than calculated. Major increases in lime requirement occurred below the pH range 5.0 to 5.5 and were ascribed to retention of protons in the form of ionic complexes with Al and Fe. Uniquely greater residual acidity from (NH4)2SO4 may have been due to greater exchange affinity and base displacement by hydroxy‐Al‐SO4 complexes as compared with complexes with monovalent anions (Cl‐, NO3‐). It is proposed that a fundamental objective of liming practice is to maintain soil pH well above the range where pathways of proton transfer are dominated by mobile sesquioxide buffer systems.

Synopsis Data on yield components, culm size and straw‐grain ratio, percentage composition, and accumulation of N, P, and K, and the weight and distribution of roots indicate that the greater growth and accumulation of nutrients of plants grown on plots with the narrowest row spacing distance was more likely the result of better utilization of light in photosynthesis than any difference associated with the root system.