Prelim 3 Flashcards
What is rice and what area of earth is it grown on?
Perennial, semi aquatic, 10% of land, 82 % on small farms
> 90% consumed in country where produced, feeds 50% of population, yield challenge
Largest producers of rice
China and India
Major exporters of rice
India and Thailand
Where is rice produced in US
Small amount in California and next to Texas
Average global rice yield
4.49 t/ha
Types of rice
Paddy/raw then brown rice then parboiled or polished (long grain, short grained, aromatic, sticky) can also go to rice bran
When is nitrogen applied to rice
Seeding, after transplanting, right after start of reproduction phase
Rice cropping systems
Upland: shifting cultivation and permanent agriculture (4-9%)
Rain fed lowland: drought prone, favorable (20-36%)
Irrigated: 50-75%
Rain fed lowland: drought and submergence prone
Flood prone: 5%
Get greater yield, fertility, and higher inputs with watered lowland ones
Differences between upland and lowland rice
Under drought, aerobic (upland) maintain nodal root production, elongation, and branching so less reduction in dry matter production
Aerobic genotypes equally tolerant under waterlogged conditions
Aerenchyma
Formed in roots during hypoxia for rice
Upland rice growing
Not always sloping land, slash and burn or Swidden agriculture used, Lower yields but not always, high diversity in varieties, 200 million practice still
Cons: low yields and low soil fertility, increasing acidity, weeds, commodity crop, labor, viability of Swidden given state policies
Irrigated lowland rice or paddy
Highly productive, sustainable at low to medium low, ecological weed control, more optimal nutrient availability near neutral ph, beneficial microbes but also methanogens, fish, crabs, frogs
Land prep:
Irrigation system, pumping, bund repair, straw incorporation or burning, puddling, tillage
Puddling:
Intentional destruction of soil aggregates by repeated plowing or harrowing under flooded conditions which seal soil and create hard pan for retaining water, nutrients, controlling weeds, leveling land, and easing transplanting
Rice nursery and transplants
Seeds are soaked then grown at high density for 15-21 days (more means transplant shock) then leaves are cut prior to transplanting
Transplanting vs direct seeding
Proper spacing increases yields by 25-40%. 10-25 cm
Rice growth
Early weeding after transplant, tillering, avoid snail damage, 90-200 before harvest, flag leaf turns yellow and panicle drops, harvest at 20-25% moisture, rats and birds are problems near harvest or earlier
Post harvest drying and milling
Dry to 14-15 % moisture, long term storage in husks, exported as milled rice
Nitrogen dynamics in rice
Paddy rice N recovery 20-40%
Upland rice 50%
Soil nitrate levels increase during drain and decrease during reflows
To improve nitrogen recovery: split applications, deep replacement fertilizer (pelleted urea), green seeker gauge, lead color chart for detecting deficiencies, green manures
Rice issues, trends, and future
C3 to C4 from Gates Foundation
Hybrids
Golden rice
NERICA - new rice for Africa, rice crossed with glaberrima
Strategic approaches to genebank: seeds of 180000 accessions of rice in IRRI gene bank
Labo/Mechanization
Water and environmental management: methane, N2O, alternate wetting and drying (AWD), aerobic rice, more crop per drop, raised beds
Solutions for rice
Increase yield more rapidly to 5.3 t/ha
Breed low methane rice
Remove rice straw, incorporate straw: not possible at scale
Reduce flood periods (AWD, aerobic, dry seed): not possible in most of Southeast Asia
Reduced or optimized nitrogen management: nitrification inhibitors, NH4SO4: very difficult with fertilizer prices and ease of urea use
SRI: remains unproven, collection of BMPs, and nonsense
