Nitrogen recovery and downslope translocation in maize hillside cropping as affected by soil conservation.

Publication Type

Journal contribution (peer reviewed)

Authors

Tuan, V. D., Hilger, T., Vien, T.D., Cadisch, G.

Year of publication

2014

Published in

Nutrient Cycling in Agroecosystems

Band/Volume

100/3

ISBN / ISSN / eISSN

1385-1314

DOI

10.1007/s10705-014-9657-2

Page (from - to)

19

We conducted a field experiment on a 53%-slope in Northwest Vietnam using ¹⁵N-labelled urea to trace its fate in maize (Zea mays) under intensive tillage and fertilization (T1, control) vs. maize with Panicum maximum grass barriers (T2), under minimum tillage (MT) with Arachis pintoi as cover crop (T3) or relay cropped with Phaseolus calcaratus (T4). ¹⁵N-labelled urea was applied to one maize row at the top of each plot one year after trial establishment. At harvest, 21.6% of the labelled ¹⁵N were recovered by maize in T1, 8.9% in T2, 29% in T3, and 30.9% in T4. In T2, maize and P. maximum competed heavily for N with a total 38.1% of ¹⁵N recovered in barriers. Less than 6% of ¹⁵N applied was found in maize rows along the slope regardless of the treatment. MT reduced ¹⁵N translocation to deeper soil layers (40-80 cm), indicating a safety net function.  Less than 0.1 kg N ha^-1 of applied ¹⁵N reached the collection devices at the bottom of plots; the majority of added ¹⁵N was intercepted by plants along the slope. Current farming practice (T1) induced a negative N balance of -142 kg N ha^-1 in which residue burning and erosion were major pathways for N losses. Reduced N losses by erosion in T2 contributed to a less negative N balance as compared to T1. Positive N balances of MT treatments were associated with strongly reduced N losses by erosion and abandonment of burning residues, indicating a viable option for hillside cropping.