Agriculture Reference
In-Depth Information
during a single growing season for cherry tomato, which extended for 183
and 190 days in the organic and conventional greenhouses, respectively,
the total irrigation amounts (applied through drip irrigation) were 3440
and 3570m
3
ha
−1
, respectively (Fig. 2). Throughout the growing season,
irrigation in the conventional farm gradually increased with the plant
growing phase until the middle of the season, while on the organic farm
irrigation is kept relatively constant throughout the entire season. In both
greenhouses, the growing season began with an establishment irrigation
of 200-240m
3
ha
−1
. In general, establishment irrigation is implemented
to prepare the upper soil for the new planting and down-leaching of salts
such as sodium chloride that have accumulated in the root zone during the
previous season (Yin et al., 2007; Ben-Gal et al., 2008). In addition, in the
organic regime, the establishment irrigation enhances the mineralization
of nutrients from the compost in the soil for plant uptake.
Total N-fertilizer implementation in both greenhouses from their es-
tablishment date (3164 yr) was very similar, 3800 and 3700 kgNha
−1
for
the organic and conventional greenhouses, respectively. In the organic
greenhouse, 98% of the N was applied as compost (processed from dairy
farms and poultry manure) that was mixed with the soil between the grow-
ing seasons, and guano (seabird excrement) that was embedded in the top
soil by the plant stems during the growing season. In the conventional
greenhouse, on the other hand, only 45% of the N was applied as compost,
mainly as a soil amendment in the early stages after the establishment of
the greenhouse, while the rest was provided through the drip irrigation
system, as mineral liquid fertilizer from industrial sources.
14.3.2 NITRATE LEACHING IN THE VADOSE ZONE
Water samples from the vadose zone and groundwater were collected at
both sites every 3 to 6 weeks for 19 months (total of 262 water samples).
A comparison of nitrate concentrations in the vadose zone pore water at
the two sites throughout all sampling campaigns exhibited a striking dif-
ference (Fig. 3). Nitrate concentrations below the root zone (>1 m) under
the organic greenhouse exhibited a very high average concentration of
357 mg L
−1
, with a peak average concentration of 724 mg L
−1
at a depth
