Nitrogen

Abstract

The control of crop growth by tissue N status was examined in hybrid squash (Cucurbita maxima L.) grown in the field with 0, 60, 120 and 180 kg N/ha (as urea). Plant dry weight and tissue N concentrations were measured at 10 day intervals during growth. A quadratic regression (R² = 0.99), describing dry matter accumulation, suggested N affected the relative growth rate (linear term) throughout. However, a single linear relationship (r²= 0.93) for all levels of applied N existed between relative growth rate and tissue N concentration, suggesting this parameter exerted a control over the crop growth rate. The mechanism of this control and implications for fertiliser management are discussed.

Key words:

• Hybrid squash
• nitrogen
• relative growth rate