Agriculture Reference
In-Depth Information
which suggested that the lower compost application rate was not as economic as the
larger application rate over a time frame of five crops, at least (Chan et al. 2011b ).
In 2008, prior to the growing capsicum, the compost applications were repeated
for the compost treatments (T2 and T5) and the mixed compost treatments (T3
and T6). A further five vegetable crops were grown in the field trial following the
experiment protocols of the first five crops. The detailed results for these crops
(currently unpublished), again found that the marketable yields for the full compost
treatment matched or exceeded the yields of the farmer practice for crops capsicum,
broccoli, lettuce, cabbage and sweet corn. The most extraordinary result was for the
crop 6 (capsicum) which was the first crop grown following the second compost
application. For this crop, the full compost treatment achieved yields which were
almost double the farmers practice (  p < 0.05), whilst the mixed compost treatment
(62.5 dry t cGO ha −1 ) attained a mean yield which was more than 50 % higher than
the farmer practice yield (Fig. 7.8 ). To put the extent of the response of the cap-
sicum crop to the compost treatment (i.e., a yield of ~ 60 t ha −1 ) into context, the
farmer practice mean yield of around 32 t ha −1 for this experiment was only just
below the perceived potential yield for capsicums of 40 t ha −1 (Bartha 1983 ). The
compost treatments, therefore, helped the capsicum crop achieve its optimal level
of production. The only other crop where the full compost treatment had a sig-
nificantly higher mean yield than the farmer practice treatment was crop 8 (lettuce)
where the compost yield was ~ 22 % higher than farmer practice. The benefit cost
ratios (BCR) from the financial analysis of this experiment over ten crops with two
applications of compost for the full compost and mixed compost treatments (cur-
rently unpublished) using the same methodology and assumptions outlined in Chan
et al. ( 2011b ), were well over 1 for both the full compost and mixed compost treat-
ments. This was largely due to the fact that capsicum or bell pepper (i.e., the crop
which had a significant yield response to the compost treatment) was a high value
crop (Dorahy et al. 2013 ). These results demonstrate that such high compost input
systems can be economical for vegetable growers over the 10 crop cycle, provided
crops that are responsive to improvements in soil quality are selected for planting
early in the cropping sequence following the application of the compost.
The yield results from the ten crops grown in this compost vegetable trial dem-
onstrated that large applications (62.5 and 125 dry t ha −1 ) of a blended garden or-
ganics green-waste compost product (80-90% garden organics composted with
10-20% chicken manure) supplemented with inorganic N fertilizer was able to
match the current farmers practice (half inorganic fertilizer; half poultry manure)
for the Sydney Basin region based on vegetable crop marketable yields. The results
also demonstrated that some crops, in terms of their marketable yield, are more
responsive to soil quality improvements than others. This experiment revealed that
capsicum was one such crop. It is, therefore, important to evaluate local crops to
establish which crops are more responsive to soil quality improvements, and ensure
that they are planted as the first crops following the application of compost. If these
are also high value crops like capsicum, then the chance of maximising economic
return may also be increased.
Search WWH ::




Custom Search