GRAIN-YIELD TRENDS OF FIELD PEA (PISUM-SATIVUM L) IN SOUTH AUSTRALIA

The grain yield of field pea (Pisum sativum L.) between 1959-60 and 19 91-92 was examined in selected Hundreds in important pea-growing regio ns of South Australia. Over the 33 years, the rates of increase in gra in yield have been substantial, ranging from 20 to 48 kg/ha.year. The rate of increase in the State average for the same period was 22 kg/ha .year. The largest rates of increase have occurred mainly in the Hundr eds in the higher rainfall areas. Yields have increased irregularly. D uring the 1960s grain yields rose relatively slowly, but from the mid 1970s to the mid 1980s, large increases occurred. Since then, yields h ave increased relatively little or, in some Hundreds, declined. With o ne exception, grain yield was positively and significantly correlated with seasonal (April-October) rainfall in each Hundred, but there were few significant correlations with rainfall in individual months. Yiel d was often correlated with winter and autumn rainfall but not with sp ring rainfall. The efficiencies of seasonal water use in the Hundreds ranged from 2.7 to 4.8 kg/ha.mm; these were lower than the maximum val ues recorded for other winter grain legumes, suggesting that water use efficiencies can improve substantially.