Impact of Climate Variability on Yield of Spring Wheat in North Dakota

Agricultural production is highly dependent on the climatic variability of the specific regions. Differential climatic and soil conditions bring about changes in yield, quality of crops thus affecting the economy. This study evaluated the impact of variability in different climatic factors keeping the other factors constant on spring wheat production in North Dakota from 2007 to 2011. The spring wheat yield mainly depends on the climatic changes during growing periods April to September. Average maximum air temperature was significantly different from April to September except June from 2007 to 2011. High average minimum and maximum air temperatures during planting time increase yield and planting area for 2010. In 2011, low mean soil temperature, excess rainfall in April caused low yield of spring wheat. The unmitigated climate variability will result in declines in yields. So, adoption of sustainable agriculture practices helps the farmers to develop the different practices for their farms.


Introduction 1.General
The impact of climate change and its changeability is a matter of concern in agriculture and is used to resolve food security issues.Climatic conditions all over the state are not same.It depends upon location to location.Crop production depends upon the climate and area.When climatic and soil conditions are normal or favorable for a crop, then there would be a high yield of crop with the best quality as well.If condition differs from normal, then it affects the yield and quality of the products.Sometimes it causes damage of crop.Besides, most of the farmers are not aware about the suitable agriculture practices like sowing time, irrigation and fertilizer application scheduling etc. with reference to climatic and soils conditions.Crop diseases or pest infestation are also depend upon the local weather and planting time.The climate variability and the area where crop is grown are very important for the crop production.So, it automatically affects the economic condition of producers, consumers and government agencies.If crop yield is less, then price for those commodities is high for the consumers and overall affects the economy.So it is very important to grow the crop according to favorable conditions.It is important for the farmers to follow the instruction given by the research scientist and extension specialist like sowing date, irrigation application time and quantity, fertilizers application recommendations etc. because they work on the model and study the possibility of benefits and damage.Most of the farmers are not aware of different technologies, techniques and model study which help them in gaining economic benefits from the crops in different locations and also at different time.
Economic distribution in any country varies with the regions, crop and their environment.Yield of crop changes with grower's responses towards the crop like new varieties of the crop adoption, fertilizer and irrigation application changes, temperature and precipitation and are the major factors.Producers are more concern with the maximum benefits per acre.Cost of the product, quality, demand, procuring capacity is all depended upon the supply and the price changes.If prices are high then the consumer reduces their consumption or sometime stops it.So, it tends to less or no use of that commodity then comes to reduction in supply and overall affects the total welfare.So it is important to make the equilibrium between prices and quantities of the product.Product is from field by the grower and depends upon the climate and other factors for the production.Protect the crop from unavoidable changes from the climate from the longer term.At farms, the impact of climate change and its variability on crop production is calculated and helps the farmers to develop the different practices for their farms.It is used at a regional level at different spatial scales and determines the impact of climate change.
In North Dakota, blizzards, floods, droughts, tornadoes, hail storms, thunderstorms, high winds, severe cold spells, and extreme heat are common.Cyclical droughts with semi-arid conditions are common in the western half of the state.The eastern half receives most of the precipitation as rain in the spring and summer [1].Agriculture is the largest industry in North Dakota, with wheat contributing the most to North Dakota's agricultural production [2].The climate of the Northern Great Plains of North Dakota proved to be the best for spring wheat.It is planted from April to May and harvested from August to early September.The soil is considered the richest agricultural land in the world and ranges from thick black loam to more porous, sandy soil [3].The rich black soil with high organic matter and the dry hot summer is ideal for the growth of wheat or other small grains.It is mostly grown in the Northern plains of the states.Local weather, soil condition, crop management and genetic information are used to predict the growth development and yield of the crop.

Objectives
The project evaluated the impact of variability in climatic factors on spring wheat production in North Dakota from 2007 to 2011.The objectives of the study are: • Study the climate variability from 2007 to 2011.
• Change in spring wheat yield from last five year of data from 2007 to 2011.
• Study the impact of climate variability on spring wheat yield.

Literature of Review
The aim of climate variability impacts assessment is to increase the understanding of the regional and global effects of climate change on agriculture.Climatic factors include change in temperature, precipitation, and higher atmospheric CO 2 concentrations etc. Worldwide, scientists are working and modeling the effect of climate change on agriculture.This is very critical issue for society because people are fully dependent upon the climate for their survival.
Studies on the plant system and crop yield have shown that environmental factors like temperature and precipitation may play an important role either synergistically or antagonistically in yield determination [4].It was also found that temperatures have impacts on yields and quality of many crops and increase in precipitation is useful in water shortage areas [5] [6].The regions where the requirement of soil moisture is less and the mois-ture in soils is more create problems.If possibility of drought is increased then the demand for irrigation may also increase [7].
Change in climate is having less effect on total food production globally but the impact of climate change is more variable on a regional basis [8].Developed countries are using new technologies and more adaptive adjustments are there but for some critically affected areas, production is affected.Agriculture is influenced by weather during growing season and soil of that area.The solution for increased crop productivity to predict the weather conditions ahead of time.So, better the knowledge of climate change the more efficient the response by agriculture.The scenarios for the grassland area showed that evaporation increases with increase in temperature and reduces the soil moisture accordingly.If evaporation goes for a longer time, then it can diminish the soil moisture content.So, an increase in temperature the prediction will extend the growing prairies season [9].In the prairie region, agriculture production is affected by precipitation [10].Climatic factors like soil moisture and temperature are sensitive to change agricultural areas of North America [11].Daily and annual changes in temperature and precipitation, which lead to climate change, will impact the yield of the crop.The main crop yield in USA increasing at 1 -2 percent every year constantly [12].But there are some variations in some areas and in between time period because of climate variability, use of new technologies, different crops, agricultural practices, fertilizer use etc.From the last decade, it is assumed that agriculture of North America faces severe weather conditions from time to time.So to reduce this climate related risks, soil and water conservation and crop diversification are used [13].
USDA report on North Dakota spring wheat yield (Figure 1) shows the graph for yield versus year from 1990 to 2010.In 2011, yield was18 percent below the trends of yield and the harvested area shrank 13% due to serious planting delays and summer flooding.Spring wheat is planted in more marginal land due to its variability.Farmers use certified seed rather than saved seed out of their last grain harvest last year and also involve an application of fertilizer, seed treatments, and fungicide spray.Sometime it is a financial risk for the farmer, but also a greater return when crops grow well (National Agricultural Statistics Service, U.S. Department of Agriculture).
In North Dakota, climate plays an important role in wheat yield and production.Figure 2 shows the weighted average wheat precipitation (mm) in North Dakota.It shows the precipitation for 2011 is much higher than the actual trend.Weekly crop reports from U.S. Department of Agriculture (USDA) mentioned increased incidence of disease from the wet and warm environment.Growers claimed that timely applications of fungicides were not always possible because of the extreme soil wetness.
North Dakota summer rainfall was the 8th wettest on record out of 116 years.Excessive rainfall spoiled the North Dakota spring wheat harvest, 48% above normal in the summer growing season.The June-August rainfall was 299.7 mm and 44% above normal (NOAA-National Oceanic and Atmospheric Administration).Crop production depends upon climate and area.When growing conditions are normal or favorable to crop, then there would be a bumper crop.If conditions differ from normal, then it affects the yield and quality of the products.It can cause damage to crop.The risk cannot be eliminated but can be minimized with contact to timely management  that would permit farm managers to display crop condition to evaluate crop yields former to harvest.National Agricultural statistics service, USDA, North Dakota field office had made surveys completed by producers and dealers of the crops.This survey help the farmer in collecting past year information regarding crop, production, yield, area harvested etc. according to area wise.

Selection of Locations
Three location of North Dakota are selected for the study are Cavalier, Grand Fork, and McHenry randomly because these locations are very good for spring wheat growth and mostly grown in northern plains of the state.

Selection of Wheat Type
Hard red spring (HRS) wheat has selected in this study.Wheat (Triticum spp.) [14] is a cereal grain.Spring wheat does not require exposure to cold temperatures for normal growth and development.It can be planted in spring.Spring wheat is sown in the spring and harvested in early fall.Spring wheat is the staple food and is planted in April to May and harvested in August to early September.It is mostly grown in northern plains of the states.The productivity data in the three countries are given in Tables 1-3.

Weather Data
Climate data for last five year from 2007 to 2011 were collected for Cavalier, Grand Fork and McHenry in North Dakota.It is collected from sowing time (April) to harvesting time (September) for spring wheat.It includes monthly average maximum and minimum temperature, average soil temperature, total solar radiation, total PET (potential evapo-transpiration) and rainfall.The data for each year and county is presented in Tables 4-18.

Statistical Analysis
In the present study, data on yield was collected from the National Agricultural Statistics Service data (NASS, USDA) and climate data from NDAWN from 2007 to 2011.The tables of climate data from April to September for 5 years from 2007 to 2010 are attached in appendix.In this study, the statistical software SAS enterprise 4.3 was used for the analysis of the data and means separation was done using Fisher's least significance difference (LSD) at 95% Significance level.Fisher LSD test is used for the comparison of two or more means.This test can only be used when significant result is attained after the analysis of variance (ANOVA).The Fishers LSD test is basically a set of individual t tests.The formula for the least significant difference is:    where: t = critical value from the t-distribution table with a df (degree of freedom) from the denominator of the f statistic.MSE = mean square error, obtained from the ANOVA test.n = number of scores used to calculate the means.
In an attempt to improve the predictions, the coefficients of determination (R 2 ) were also computed in model summary which shows how well the data fits in the statistical model that is being used.The R 2 value ranges from 0 to 1 which then can be computed as percent to provide a better representation of the data.Higher R 2 gives better the prediction of dependent variables indicating better model to be used for future outcomes.
during the study period is given in Tables 19-25.It also includes the coefficient of determination (R 2 ) value which helps us to indicate the quality prediction of dependent variable.Analysis shows that in most cases the average air maximum temperature, average minimum temperature, average soil temperature, total solar radiation, total PET and rainfall significantly different in each month from the year 2007 to 2011.However, there are some exceptions and data analysis revealed that there were no significance difference in June for average maximum temperature from 2007 to 2011 and June, August for average minimum temperature.The mean average soil temperature in May, July, August, and September for year 2007 to 2011 are not significantly different.In case of total solar radiation as well, there are months of May, June, August and September which did not show any significant difference.The mean total PET in April, June, August and September for 2007 to 2011 were not found significantly different.Similar observation is made for the mean rainfall in July for year 2011, 2007, 2008 and 2010 which are not all significant to each other.

Agricultural Overview
North Dakota's major industry is agriculture.Planting and yield progress for three counties (Cavalier, Grand Fork and McHenry) was taken as average from 2007 to 2011 (Table 25).There was a change in agricultural production from 2007 to 2011, which results from the changes in yields and changes in crop acreage.Changes in crop yields are due to the variability in climate and changes in acreage.The yield fluctuates due to the damage of some portion of sown crop because of the significant difference in planting and harvesting area.
From Table 25, it was shown that higher average planting area in 2008 was 98,477 hectare with yield 3.141 MT/ha and yield was higher in 2010 as 48.5 with average planting area as 92,002 hectare.It was shown that the harvested area in hectare is less than the area planted in hectare.Production in metric tons is depending upon Yield MT/ha) and area harvested.Area planted and harvested was increased from 2007 to 2008 followed by yield.Yield of 3.208 MT/ha from 87,011 hectare of planted area in 2009 and 3.282 MT/ha from 92,002 hectare in 2010 which was higher than 2007, 2008, and 2011.
There are number of factors which affect the decrease in planting area like high water table, climate, soil condition, variety of spring wheat, some agronomic factor, weeds, pest, and diseases etc.
In this study, climatic factors are used and other factors are keeping constant.The impact of climate variation on spring wheat yield in North Dakota depends on the actual patterns of climatic factors change during growing In 2007 and 2008, timely rains and moderate temperatures helped spring wheat to grow very well.A favorable weather condition increases the spring wheat planting area and it also increase the yield.In 2009, the planting days for spring wheat were dry across the State with snow in the northeast regions.The middle of the month had more rain showers across the State.In 2010, Warm, dry weather at the time of planting allowed producers to begin planting, temperatures and precipitation was above normal.Harvest was in progress and aided spring wheat development in end of August.
Crop establishment was a problem when soil temperatures are low.Plant emergence and its establishment for crop growth are affected.Yield was limited by amount of water received and stored in the soil during April 2011.In 2011, Temperatures was below normal during planting of spring wheat and precipitation was above normal.Freezing rain and snow added moisture to the already wet fields.Flooding remained a problem across the state.So, planting of spring wheat was pushed back again due to saturated fields and low soil temperatures.Late planting season and more acres were planted to other crop.Transpiration is a heat avoidance mechanism.A crop that maintains transpiration cooling may be a good heat avoider.The temperature of spring wheat standing in the field may be different from air temperature by some degrees.Transpiration rate is affected by these differences in air and soil temperature.Air temperature increases with increase in leaf temperature, when stoma of leaves closes due to water shortage.During planting time, solar radiation (385.33 Lys) and potential-evapotranspiration (89.7 mm) for 2011 was less.Solar radiation affects photosynthesis, transpiration, and also used to make plant biomass.Excess of rainfall in field affect the yield by flooding.There was also the stress prior to harvest of spring wheat in these locations.

Figure 1 .
Figure 1.North Dakota spring wheat yield from 1990 to 2011 (Data source USDA).

Figure 2 .
Figure 2. North Dakota's precipitation index in wheat growing season from the year 2007 to 2013.

Table 1 .
Agriculture data for spring wheat in Cavalier county, North Dakota in 2007-2011.

Table 2 .
Agriculture data for spring wheat in Grand Fork county, North Dakota in 2007-2011.

Table 3 .
Agriculture data for spring wheat in McHenry county, North Dakota in 2007-2011.

Table 4 .
Climate data for spring wheat in Cavalier county, North Dakota in 2007.

Table 25 .
Mean agriculture overview from 2007 to 2011 for Cavalier, Grand Fork, and McHenry in North Dakota.