Climate, Soils, and Seed Production. Thomas G Chastain CSS 460/560 Seed Production

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1 Climate, Soils, and Seed Production Thomas G Chastain CSS 460/560 Seed Production

2 Climate and Seed Production Much of the land mass of the Eastern US is wetter than the Western US. There are individual areas within the west that are arid or semi-arid whereas a few areas have a wet climate. Summer rainfall favors annual seed crops such as maize and soybeans which grow in summer and are primarily produced east of the Rocky Mountains. US Average Annual Precipitation Map Source Oregon Climate Service

3 Climate and Seed Production The dry summer climate of the western US was the main reason for the westward migration of the forage, turf and vegetable seed industries from the east. Average Oregon July Precipitation Map Source Oregon Climate Service

4 Climate and Seed Production The climate of the Pacific Northwest climate favors winter annuals and cool-season perennials, seed crops that actively grow over winter and can be harvested early in summer. Rainfall subsides as these crops mature in early summer facilitating harvest. Other seed crops are irrigated in the dry conditions prevalent in summer. Corvallis Precipitation

5 Climate and Seed Production Mild winter climate in Oregon permits production of winter annuals such as annual ryegrass unlike the northern Great Plains states located at the same latitude. US Annual Ryegrass Seed Crop Acreage One dot = 300 acres Map Source Oregon Climate Service

6 Climate and Seed Production A Oregon Average Annual Precipitation C B A B C A - Annual ryegrass production in Willamette Valley B - Roughstalk bluegrass with aid of surface irrigation in central Oregon C- Kentucky bluegrass under center pivot in Grande Ronde Valley

7 Climate and Seed Production Rainfall prior to harvest can result in pre-harvest sprouting and can reduce seed quality. Mild winter climates reduce the incidence of winter injury in perennial seed crops. Irrigation can be applied to seed crops only when needed in dry climates. Dry climates reduce the incidence and spread of some plant diseases. Center pivot in grass seed field (top), sprouted wheat seed (bottom)

8 Climate and Seed Production Low rainfall and low humidity at harvest make field drying possible. This reduces the need for artificial drying of the harvested seed prior to storage and favors perennial seed crops. Artificial drying increases the cost of production. Dried windrows can later be threshed by a combine with a pickup header. In areas with wet summer climates, seed crops are direct combined without the aid of field drying. Swather in tall fescue seed field (top), windrows in Kentucky bluegrass seed field (bottom)

9 Tall fescue rust (top), aerial herbicide application John Mc Manigal photo (bottom) Climate and Seed Production Weather conditions have a strong effect on the development of important diseases in grass seed crops such as rust. Warm springs tend to have more rust than cool springs. Herbicide behavior can be affected by low temperature and degree of cloudiness, as well as affecting crop tolerance to herbicides. Dry late summer and autumn conditions can reduce crop stands and seed yields in several grass seed crops.

10 Yield of Willamette Valley Grass Seed Crops Yields for most grass seed crops have increased over time, but not annual ryegrass. Is there a specific effect of climate or weather on these changes?

11 Yield of Willamette Valley Grass Seed Crops Annual precipitation had no effect on seed yields was the driest year and 1996 was the wettest, but neither year had an extraordinary influence on seed yields inches inches

12 Yield of Willamette Valley Grass Seed Crops WF, WS WF, DS DF, DS DF, WS DF, WS WF, WS Seasonal precipitation is more important than annual precipitation. Too much or too little rainfall in spring produces poor yields regardless of fall conditions. Dry fall (DF) weather in combination with too wet (WS) or too dry spring (DS) weather also produces low yields.

13 Autumn Rainfall Crop regrowth is influenced by rainfall in the autumn. Yield components affected by fall rainfall include plant stand and fertile tiller number. September and October rainfall effects on seed yield in tall fescue

14 Spring Rainfall Dry Wet Several critical plant processes are affected by rainfall during this period, including flowering, pollination, and seed filling. Too much rainfall in spring increases lodging and reduces pollination, both cause reduced seed yield. Too little rainfall in spring produces poor yields because of poor seed set and seed filling. May and June rainfall effects on seed yield in annual ryegrass

15 Climate and Seed Production A B Drought Stress No Drought Stress Late summer and fall drought contributes to premature stand loss in perennial ryegrass seed fields. Note that dead plants are interspersed among living plants in the top photo (A). When perennial ryegrass plants are exposed to controlled drought stress, some of the plants died and some survived in a pattern similar to that observed in the field (B). Some genotypes within cultivars exhibit greater drought tolerance than others.

16 Climate and Seed Production A 120 C Total Autumn Tillers (10 2 m 2 ) B Soil Water Potential (MPa) Autumn tiller production in perennial ryegrass and soil water (a), TDR system for measuring soil water (b), regrowth in irrigated perennial ryegrass (c), non-irrigated (d) D

17 Climate and Seed Production Average late summer rainfall in the Willamette Valley is less than 3 inches. But 4 inches of rainfall may be needed during this period to maintain stands. Rainfall reaches or exceeds 4 inches in less than one in five years during late summer. Dryland perennial ryegrass may experience some stand loss in more than 80% of the years. Rainfall is less than 1 inch in nearly one third of the years in late summer

18 Climate Change and Seed Production Seed yields of several grass seed crop species have increased over the last 35 years. Seed yield increases in the region over this period ranged from 292 kg/ha for annual ryegrass to 1147 kg/ha for tall fescue. This period has been marked by an increase in average temperature of less than 0.3 C. Seed yield has not been adversely affected by the small increases in temperature, and in fact, seed yield has increased.

19 Soils and Seed Production The inherent productivity of soils determines the seed crops that can be grown. Soil drainage, steep terrain, and erosion potential limit the cropping choices of fields for the production of seed crops. 12 Dayton Silt Loam 14 Bashaw Clay 36 Amity Silt Loam 155 Waldo Silty Clay Loam 170 Willamette Silt Loam 177 Woodburn Silt Loam Sugar beet seed field in flood plain

20 North Willamette Valley Eola Hills Salem Woodburn Waldo Hills Soils and Seed Production Flood plains and other bottom lands 293,300 acres (29%). High to low productivity soils with very good to poor drainage. Alluvial terraces 410,295 acres (42%). High to low productivity soils with good to very poor drainage. Hill soils 293,300 acres (29%). Intermediate to low productivity soils with moderate to high erosion hazards. Hill Alluvial terrace Flood plain River Alluvial terrace Hill

21 Soils and Seed Production Flood plains have the highest proportion of high productivity (Class I) soils (56%), and have the greatest diversity of cropping choices and the greatest number of irrigated acres. Alluvial terraces have the next highest proportion of Class I soils (47%), and much greater amounts of intermediate (Class II) and low productivity (Class III and IV) soils. Drainage issues limit productivity most on the alluvial terraces, and have fewer cropping choices and less irrigation. Hill soils are dominated by intermediate and low productivity soils with hill slopes and erosion hazards being factors limiting crop choices. Corvallis Eugene South Willamette Valley

22 Soils and Seed Production Flood plains High productivity soils (Chehalis, Newberg) vegetable, flower, sugarbeet, grass, and legume seed crops. Low productivity soils (Bashaw, Wapato) poor drainage reduces crop options to grass seed. Alluvial terraces High productivity soils (Woodburn, Willamette) perennial ryegrass and tall fescue seed crops and wheat predominate without irrigation. Low productivity soils (Dayton, Conser) are limited to annual ryegrass without drainage systems. Hill soils Intermediate (Jory and Steiwer) and low productivity soils (Nekia, Hazelair) are home to fine fescue, perennial ryegrass, and tall fescue seed crops. Corvallis Eugene South Willamette Valley Crops