Sensitivity of yield and grain nitrogen concentration of wheat, lupin and pea to source reduction during grain filling. A comparative survey under high yielding conditions Patricio A. Sandan ˜a a,b , Claudia I. Harcha a,b , Daniel F. Calderini b, * a Graduate School, Faculty of Agricultural Sciences, Universidad Austral de Chile, Chile b Institute of Plant Production and Protection, Universidad Austral de Chile, Campus Isla Teja, Valdivia, Chile 1. Introduction Sensitivity of crops to source–sink manipulations has been investigated to assess clue phenophases for grain number determination (e.g., Fischer, 1975, 1985; Kiniry and Ritchie, 1985; Jiang and Egli, 1993; Cantagallo et al., 2004; Arisnabarreta and Miralles, 2008; Estrada-Campuzano et al., 2008) and to evaluate whether the yield is either source or sink limited after grain setting (Fischer and HilleRisLambers, 1978; Slafer and Savin, 1994; Egli and Bruening, 2001; Cartelle et al., 2006; Calderini et al., 2006; Gambı ´n and Borra ´s, 2007; Beed et al., 2007). These studies have provided the information necessary to develop conceptual and mathematical models of grain yield determination for different crops, which in turn, created useful tools for increasing both potential and actual yields (see Sadras and Calderini, 2009). Despite the huge gains in scientific knowledge about grain yield determination, the degree of understanding reached among crops is clearly different. Tempe- rate cereals, mainly wheat, have been much more investigated than temperate grain legumes like lupin and pea. This makes it hard to compare yield responses between these crops and to estimate their behaviour in different environments. In the agricultural systems of Southern Chile it is essential to make these types of comparisons considering that wheat is the most sown grain crop and narrow leaf lupin has become increasingly important in the last decade due to its potential as a source of proteins for the salmon industry (ODEPA, 2009). In addition to lupin, pea could also be considered as an alternative crop for plant protein production taking into account its high yield potential in Southern Chile (higher than 7 Mg ha 1 ). Field Crops Research 114 (2009) 233–243 ARTICLE INFO Article history: Received 14 April 2008 Received in revised form 2 August 2009 Accepted 8 August 2009 Keywords: Wheat Lupin Pea Grain number Grain weight Grain nitrogen concentration Source–sink ratio ABSTRACT Several studies have been conducted to evaluate the response of crops, especially temperate cereals, to different source–sink ratios during grain filling. However, there is much less information about temperate legumes and even less work comparing the two. The objective of this study was to evaluate the response of both grain yield and grain nitrogen concentration of wheat (Triticum aestivum L.), narrow-leafed lupin (Lupinus angustifolius L.) and pea (Pisum sativum L.) to similar source reduction during grain filling. Two field experiments were conducted in a high yielding environment of Southern Chile. In experiment 1 wheat and narrow-leafed lupin were grown for two consecutive years. Experiment 2 evaluated wheat and pea on two sowing dates. In both experiments a reduction in the source–sink ratio was imposed by using black nets that intercepted 90% of the incident solar radiation from the commencement of the linear dry matter accumulation to physiological maturity. Grain yield was differentially (p < 0.01) decreased by the source reduction in lupin (98%), wheat (63%) and pea (26%). Given that these experiments were carried out in a high yielding environment, the higher response of wheat relative to previous studies supports the hypothesis that the higher the yield potential, the higher the source sensitivity of this crops during the grain filling period. On the other hand, source reduction positively affected (p < 0.05) grain nitrogen concentration in wheat (66%) and pea (18%) but negatively affected lupin (40%). The higher sensitivity of grain yield compared to that of grain nitrogen yield was the cause of the positive effect of the lower source–sink ratio recorded in wheat and pea. In contrast, source shortage in lupin decreased grain nitrogen concentration probably as result of the quick response of grain growth to source limitation. The contrasting sensitivities of lupin, wheat and pea to source reduction during grain filling prevent us to see grain yield and quality response of these crops as separate groups, i.e. temperate cereals vs. temperate legumes. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +56 63 221723; fax: +56 63 221233. E-mail address: danielcalderini@uach.cl (D.F. Calderini). Contents lists available at ScienceDirect Field Crops Research journal homepage: www.elsevier.com/locate/fcr 0378-4290/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2009.08.003