After crop harvesting, five soil cores 100 cm in
depth were taken from each plot and each then sectioned
into portions of the following depths: 0–20,
20–40, 40–60, 60–80 and 80–100 cm. Portions corresponding
to the same depth were mixed as one composite
sample to determine soil NO−
3 -N and soil moisture
contents. Other soils were air-dried and sieved
(< 2 mm) for chemical analysis. Tomato fruits were
harvested several times during the growth period, and
plants were sub-sampled from each plot at every harvest
date to calculate fresh weight. Each plant was
separated into shoot and fruit; belowground residues
were not considered. Straw samples were oven-dried
at 70 ◦C and weighed to obtain the dry matter weight.
Samples were ground and filtered through a 2-mm sieve
for nutrient analysis.