J. Vos et Pel. Van Der Putten, Field observations on nitrogen catch crops. III. Transfer of nitrogen to the succeeding main crop, PLANT SOIL, 236(2), 2001, pp. 263-273
In temperate climates with a precipitation surplus during autumn and winter
, nitrogen (N) catch crops can help to reduce nitrogen losses from cropping
systems by absorbing nitrogen from the soil and transfer it to a following
main crop. In two field experiments the catch crop species winter rye (Sec
ale cereale) and forage rape (Brassica napus ssp. oleifera (Metzg.) Sinsk)
or oil radish ( Raphanus sativus spp. oleiferus (DC.) Metzg.) were planted
end of August and 3 weeks later with a non-limiting supply of N and zero-N
controls. In the next spring catch crops were incorporated into the soil. I
n Expt 1, N transfer was measured as (i) the N uptake of a potato test crop
, grown with zero and 12.5 g m(-2) N applied, and (ii) the increase in soil
mineral N (0-30 cm) in uncropped soil covered with polythene film. In Expt
2, N transfer was measured as the increase in soil mineral N in covered cy
linders placed in uncropped soil (in situ incubation). Subsidiary laborator
y incubations were performed in Expt 2. In Expt 1, the apparent recovery in
potato of fertilizer N (R-f) was 0.56. The recovery in potato of N mineral
ized from 'native' N pools other than catch crop material (R-n) ranged from
0.43 to 0.51, depending on the value assumed for the depth of N extraction
by potato roots. The average recovery in potato of incorporated catch crop
N (R-c) was 0.34. Expressed as 'fertilizer N replacement factor' (F-r) the
latter was 0.61 (i.e. 1 kg of N in catch crop material counts for 0.61 kg
fertilizer N). Under the film in Expt 1 the fraction net mineralization of
incorporated catch crop N (M-n) was 0.36 on August 11 and 0.43 on October 1
8. In Expt 2, the average value of M-n was 0.31, which was lower than in Ex
pt 1 and probably associated with the drier soil in Expt 2. In the laborato
ry incubations (20 degreesC) M-n showed values up to 0.54 after 84 days wit
h the largest rates of change in mineralization occuring early after the st
art of the incubation. In conjunction with literature data it is concluded
that cultivation of nitrogen catch crops shows promise as a means to reduce
N input and N losses in temperate climates with wet winters.