- Author: Randall Mutters
If the current temperature trend continues then plant maturity may be accelerated as compared to the last couple of years. The National Weather Service predicts warmer than normal August temperatures in the Sacramento Valley (http://www.cpc.ncep.noaa.gov/products/predictions/30day/). In the 2014 Statewide Variety Trials, panicle initiation was ahead of the expected plant development schedule by about 7 days.
Remember that the rate of drying for M-202, M-205 and M-206 varies between years. For example, in a ‘warm' year (e.g. 2009) the rate of moisture loss from the maturing kernel was double that of a ‘cool' year (e.g. 2010). In this case, the average rate of moisture loss across varieties was 0.8 percentage points per day as compared to 0.4 in the cooler year (Table 1).
Table 1. Daily moisture loss in percentage points from M-202, M-205, and M-206 2009 & 2010.
Keeping close track of grain moisture is particularly important in warm harvest seasons. M-105, M-205, and M-206 can be harvested at quite low moisture contents without compromising milling quality. However, there are limits to this resilience. Rice at a moisture content of less than 17-18% will crack if rehydrated by prolonged dew or rain. The harvest season over the last few years have been unusually dry with very few hours of dew. Consequently it was possible to harvest high quality rice at very low moisture contents. An El Nino weather pattern is developing the Pacific Ocean. This may result in early rains and/or more dew events, thus increasing the chance of kernel fissuring due to rehydration in low moisture rice. Don't assume that the rice can be harvested at the ultra-low moisture levels in all years.
On a related topic, there is some concern that water supplies may run short at the end of the season in some areas. In other words, there may not be enough water to finish the crop. If you are faced with this possibility, remember that drain time experiments demonstrated that rice fields in with heavy clay soils can be safely drained 24 to 28 days after 50% heading without compromising yield and quality. Applying this concept to lack of irrigation would mean that the deep water from blanking protection would be held and allowed to slow subside; some additional water may need to be applied. The target is no standing water but the soil is still fully saturated in the intake check at 24 days after 50% heading (assuming that the water recedes in the intake check first). Compared to typical practices this could shorten the irrigation season by about 7 days. If you have any questions regarding this management option, please give me a call (530.521.6670)