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Effect of soil treatment with cereal straw and method of crop establishment on field pea (Pisum sativum L.) N2 fixation |
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| Authors: | J Evans N A Fettell G E O'Connor D J Carpenter P M Chalk |
| Institution: | 1. NSW Agriculture, PMB, Agricultural Research Institute, 2650, Wagga Wagga, NSW, Australia 2. NSW Agriculture, Agricultural Research and Advisory Station, PO Box 300, 2877, Condobolin, NSW, Australia 3. Department of Agriculture, University of Melbourne, 3052, Parkville, Victoria, Australia |
| Abstract: | The effects of soil incorporation with cereal straw (nil, 2.5, 5 and 10 t straw ha?1) and direct drilling on the proportion and amount of pea N derived from biological N fixation were investigated in three field experiments. Fixed N was determined by15N dilution using barley as a reference plant. The three sites were on acidic, red clay-loams in the cropping zone of southeastern Australia. Seasonal plant available soil N, as determined by the N accumulated in barley, was 31, 56 and 158 kg N ha?1, for the three sites. Incorporated straw reduced soil nitrate at sowing by 10–50 kg N ha?1 (0–30 cm), and 5 or 10 t straw ha?1 reduced barley uptake of N by 10–38 kg N ha?1. However, reducing plant available soil N was generally ineffective for increasing the N fixed by pea. Fixed N increased only at the site with the least plant-available N, and only one-third of the increase could be attributed to lower soil N uptake by pea. There was no evidence that direct drilling pea increased fixed N by decreasing crop uptake of soil N. It is proposed that a lower requirement for soil N by pea as compared to barley, and availability of mineral N beneath the soil layer treated with straw, minimise the effectiveness of straw incorporation for increasing the N fixed by pea. |
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