Biological nitrogen fixation, accumulation of soil nitrogen and nitrogen balance for white clover and field pea grown for seed
Kumar, K.; Goh, K.M.
Field Crops Research 68(1): 49-59, 29 September
ISSN/ISBN: 0378-4290 Accession: 034489507
The N accumulation, biological N2 fixation and simple N balance of white clover and field pea grown for seed were determined in field experiments. Both crops accumulated similar amounts of dry matter but pea accumulated more N (427 kg N ha-1) than white clover (387 kg N ha-1). However, white clover fixed 327 kg N ha-1, which was significantly higher than that (286 kg N ha-1) fixed by pea. At final harvest, the per cent N2 derived from the air (%Ndfa) was also significantly higher for white clover (90%) than pea (69%). Amounts of N2 fixed were strongly correlated with dry matter yield in both crops. There was no significant difference in amount of N2 fixed or %Ndfa when N2 fixation was estimated based on 15N enrichment of individual plant component or the whole plant. The N harvest index for both crops (4-28%) was considerable lower than %Ndfa (69-90%), and hence the overall simplified N balances for these crops were positive. The net N gain due to N2 fixation was high (171-313 kg N ha-1) and may play an important role in the N benefits to subsequent crops and/or contribute to increased soil N fertility.