Effects of plant spacing and nitrogen fertilizer on N2-fixation, nitrogen transferred to intercrop maize and yields of the component crops in maize-groundnut intercrops
1992
Chitima Yathaputanont
Field experiment was conducted on Pak Chong soil, using 15N-Dilution Technique (ID), N-Balance (NB) and Acetylene Reduction Assay (ARA), to examine effects of plant spacing and nitrogen fertilizer on N2-fixation, N transferred to the intercrop maize and the yields of the component crops in cropping systems involving maize and groundnut. The cropping systems were (1) L1, one row of groundnut grown between maize double rows (2) L2, two rows of groundnut grown between maize double rows (3) L3, one row of groundnut grown between maize single row (4) L4, sole groundnut and (5) M, sole maize. The rate of N-fertilizer applied to the intercrop maize was 80 Kg N/ha. L1 produced not only highest corn yield (3894 kg/ha) but also highest total crop dry matter (10962 kg/ha), i.e. that of corn plus that of groundnut, regardless of N-fertilization. Both with and without N fertilizer, L2 gave higher amount of N in groundnut drived from fixation (62.6 and 43.8 %), N2 fixed per hectare (52 and 25 kg/ha) and N2 fixed per plant (0.24 and 0.12 g/plant) than L1 and L3 but lower than L4. The values for L4 were 60.4 %, 175 kg/ha and 0.44 g/plant, respectively. There was no clear evidence supporting transfer of N2 fixed by the legume to the intercrop maize, regardless of plant spacing. Quantities of fixed N2 estimated by ARA using a conversion factor of 1 and those by NB method were mostly higher than those by ID. However, the quantities estimated by the three methods were highly correlated with each other. Without N fertilizer, loss in input-output balance of N (dN, amount of N2 fixed minus amounts of N in the maize grain and the groundnut pods) for L2 was smaller than those for L1, L3 and L4. But with N fertilizer, all of the systems gave comparable dN. Considering with the corn yields and land equivalent ratios, L1 was most recommendable.
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