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The retention of litter and logging residue as a source of nutrients and organic matter for the next crop, as well as a mulch to conserve soil moisture, are recognised as primary factors influencing the productivity of successive crops of radiata pine planted on sandy soils, and are also likely to be relevant, though perhaps to a lesser extent, on more fertile soils. The influence of site and stand characteristics on the implementation of these principles is discussed with special reference to radiata pine on infertile sands.On infertile sands, improved early growth in the second rotation has been achieved from a variety of practices. In each case, the improvement appears to be largely as a result of increases in both the availability of water (weed control and/ or mulching) and nitrogen (inputs from either fertiliser, fixation by legumes, or from accelerated mineralisation of organic N in logging residue). The significance of these early results in terms of productivity over the full rotation is discussed in relation to soil water availability and studies of the influence of water and nitrogen treatments on the water-use efficiency of radiata pine seedlings.

Seedlings of Pinus radiata, 10–20 weeks old and hitherto fully watered, responded rapidly when water was withheld. Wilting occurred 9d later, at which time soil matric water potential at dawn (Ψm) was –1.06MPa and shoot water potential (Ψ) was –1.9 MPa. Small reductions in Ψm elicited large responses in assimilation rate (A) and leaf conductance to water vapour (g). Seedlings appear to be more sensitive to small water deficits than are older Plants of P. radiata. After rewatering, significant increases of A and g occurred within one day, but neither regained the values measured prior to the imposition of a single drying cycle. This residual effect of drought on A, after one or six drying cycles, was partially caused by a decrease in photosynthetic capacity. In plants wilted for the first time, the concentration of abscisic acid (ABA) in the bulk foliage increased 3.4 times as Ψ decreased to –1.77 MPa. In comparison, pretreatment with six drying cycles significantly reduced Ψ to –2.13 MPa (indicating some osmotic adjustment) and induced only a doubling of ABA concentration. However, these differences in Ψ and ABA concentration did not Persist after the plants of all pretreatments had been watered for 7 d, although g of drought‐pretreatment Plants remained approximately half that of continuously‐watered plants.