Bradbrook - 2012 - Rice Farming complete with methods to increase ric

e. Leaf color chart
Source: IRRl.org
The nitrogen content of a plant can be easily monitored using a standardized LCC
to check a leafs shade of green. This chart was developed from the collaboration
between IRJU and the Lfniversity of California Cooperative Extension. The chart is
made of a white plastic strip with four panels of different shades of green (from
yellowish to dark). Each shade corresponds to a specific amount of N in the plant.
To determine if the rice plants need supplemental N, first a sample of ten healthy
rice plants or hills are randomly selected. The topmost, fully expanded leaf from
each plant is removed and the middle portion of the leaf is used to locate the panel
color that closely matches that of the leaf. If the leaf color falls between Panels 3
and 4, then supplemental nitrogen is not needed. If the color falls below Panel 3,
then the soil is nitrogen-deficient and must be supplemented. Panel 5 indicates
excess nitrogen. In this case, fertilization should be withheld.
Leaf color readings should always be conducted at a specified time of day, and
they must be done in the shade because direct sunlight affects leaf color reading.
f. Micronutrients important to rice plant growth
Zinc deficiency is common in sodic soils with high pH or when the soil or water
that is used for irrigation contains high amounts of bicarbonate. It is considered as
the most prevalent deficiency of any micronutrient in rice. The symptoms of zinc
deficiency include stunted plants, brovm spots on leaves, basal leaf chlorosis,
stacking of leaf sheaths, slow growth, and reduced tillering. During the
reproductive stage, increased sterility of the spikelets may occur.
To correct zinc deficiency, zinc sulfate can be applied to the field at 5 kg per
hectare 14 days before transplanting. Alternatively, seedlings may be treated with
35