Deficit irrigation of rapeseed for water-saving: Effects on biomass accumulation, light interception and radiation use efficiency under different N rates
2012
Hamzei, Javad | Soltani, Jalal
Rapeseed is one of the most important oilseed crops worldwide and there is a high potential for expansion of its cultivation, particularly in arid and semi-arid regions. Management practice effects on radiation use efficiency (RUE) have not been well documented for rapeseed. It is thought that reduction of aboveground dry matter (ADM) in crops after decreased RUE occurs due to shortage of nitrogen and irrigation. To test this hypothesis, we applied deficit watering techniques to rapeseed with contrasting nitrogen supply. Treatments included three levels of nitrogen supply, namely low level (LN, 8gNmâ»Â²), normal level (NN, 12gNmâ»Â²) and high level of nitrogen (HN, 16gNmâ»Â²), in combination with three levels of irrigation (IRâ, 7500; IRâ, 4500; and IRâ, 3000m³waterhaâ»Â¹). Then, traits of ADM, grain yield (GY), leaf area index (LAI), nitrogen nutrition index (NNI), leaf chlorophyll (SPADi), capture ratio (CR), penetration ratio (PR), reflection ratio (RR), accumulated PAR (âiPAR) and RUE were measured. The ANOVA revealed that the N and irrigation treatments exerted significant effects on all traits. RUE in IRâ and IRâ treatments was comparable to, or higher than, that in IRâ (0.756 and 0.745 vs. 0.477gμmolâ»Â¹). However, the interaction of irrigation levelsÃN rates affected only ADM, GY, âiPAR and RUE. Maximum values of these traits remained unchanged at IRâÃNN, IRâÃHN, IRâÃNN and IRâÃHN combined treatments. In conclusion, the IRâÃNN treatment can be recommended for rapeseed under field conditions in order to maximize the yield.
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