The role of grain number, nitrogen nutrition and stem number in limiting pea crop ( Pisum sativum) yields under agricultural conditions

Abstract

In a small area of the Paris basin in France, 71 pea ( Pisum sativum) crops, cv. Solara, were examined to elucidate the determinants of their yield over 3 years. The yields ranged from between 3.71 and 7.81 t ha −1, and averaged 5.85, 6.25 and 6.47 t ha −1 in 1988, 1989 and 1990, respectively. The large differences observed each year among fields were essentially related to grain number, whereas mean grain weight was less variable. Grain number and pod number were highly correlated. A substantial effect of nitrogen nutrition, assessed by a nitrogen nutrition index on grain number, was observed. The role of reproductive stem number on grain number was also examined, showing a threshold at 115 stems m −2, below which, under the conditions examined, large grain numbers per stem did not compensate for low stem numbers. Furthermore, we also show that branching might not be sufficient to compensate for low plant numbers in some crops when nitrogen nutrition is inadequate, and this also leads to a decrease in grain number.