Climate Change Impacts and Adaptation in Rainfed Farming Systems: A Modeling Framework for Scaling-Out Climate Smart Agriculture in Sub-Saharan Africa

Improving agricultural water productivity, under rainfed or irrigated conditions, holds significant scope for addressing climate change vulnerability. It also offers adaptation capacity needs as well as water and food security in the southern African region. In this study, evidence for climate change impacts and adaptation strategies in rainfed agricultural systems is explored through modeling predictions of crop yield, soil moisture and excess water for potential harvesting. The study specifically presents the results of climate change impacts under rainfed conditions for maize, sorghum and sunflower using soil-water-crop model simulations, integrated based on daily inputs of rainfall and evapotranspiration disaggregated from GCM scenarios. The research targets a vast farming region dominated by heavy clay soils where rainfed agriculture is a dominant practice. The potential for improving soil water productivity and improved water harvesting have been explored as ways of climate change mitigation and adaptation measures. This can be utilized to explore and design appropriate conservation agriculture and adaptation practices in similar agro-ecological environments, and create opportunities for outscaling for much wider areas. The results of this study can suggest the need for possible policy refinements towards reducing vulnerability and adaptation to climate change in rainfed farming systems.

Spatial variability of leaf wetness under different soil water conditions in rainfed jujube (Ziziphus jujuba Mill.) in the loess hilly region, China

Leaf wetness provides a wide range of benefits not only to leaves,but also to ecosystems and communities.It regulates canopy eco-hydrological processes and drives spatial differences in hydrological flux.In spite of these functions,little remains known about the spatial distribution of leaf wetness under different soil water conditions.Leaf wetness measurements at the top(180 cm),middle(135 cm),and bottom(85 cm)of the canopy positions of rainfed jujube(Ziziphus jujuba Mill.)in the Chinese loess hilly region were obtained along with meteorological and soil water conditions during the growing seasons in 2019 and 2020.Under soil water non-deficit condition,the frequency of occurrence of leaf wetness was 5.45%higher at the top than at the middle and bottom of the canopy positions.The frequency of occurrence of leaf wetness at the top,middle and bottom of the canopy positions was over 80%at 17:00‒18:00(LST).However,the occurrence of leaf wetness at the top was earlier than those at the middle and bottom of the canopy positions.Correspondingly,leaf drying at the top was also latter than those at the middle and bottom of the canopy positions.Leaf wetness duration at the middle was similar to that at the bottom of the canopy position,but about 1.46-3.01 h less than that at the top.Under soil water deficit condition,the frequency of occurrence of leaf wetness(4.92%-45.45%)followed the order of top>middle>bottom of the canopy position.As the onset of leaf wetness was delayed,the onset of wet leaf drying was advanced and the leaf wetness duration was shortened.Leaf wetness duration at the top was linearly related(R^(2)>0.70)to those at the middle and bottom of the canopy positions under different soil water conditions.In conclusion,the hydrological processes at canopy surfaces of rainfed jujube depended on the position of leaves,thus adjusting canopy structure to redistribute hydrological process is a way to meet the water need of jujube.

Trend Analysis in Rainfall, Reference Evapotranspiration and Aridity Index in Southern Senegal: Adaptation to the Vulnerability of Rainfed Rice Cultivation to Climate Change

Rainfall and evapotranspiration are two vital elements for food production under rainfed agriculture. This study aims at investigating the combined changes in these variables in the form of aridly index in the southern Senegal. The temporal trends in annual and monthly (from May to October) aridity index, rainfall and evapotranspiration are examined and adaptation strategies to the vulnerability of rainfed rice cultivation to the changes are developed. The results show a significant decreasing trend in annual rainfall at all study locations for the period 1922-2015. When analyzing the trends in sub-periods, there are two clear patterns in the annual rainfall series: a decreasing trend for the period 1922-1979 and a reversal increasing trend for the period 1980-2015. An increasing trend is also observed in annual reference evapotranspiration. The results reveal that the region will be drier with a significant increase in aridity at the annual and most monthly series. Appropriate adaptation strategies should be implemented to diminish the adverse influence of the increasing aridity on rice productivity for a sustainable agriculture.

Impacts of oak deforestation and rainfed cultivation on soil redistribution processes across hillslopes using ^(137)Cs techniques

Background:As one of the main components of land-use change,deforestation is considered the greatest threat to global environmental diversity with possible irreversible environmental consequences.Specifically,one example could be the impacts of land-use changes from oak forests into agricultural ecosystems,which may have detrimental impacts on soil mobilization across hillslopes.However,to date,scarce studies are assessing these impacts at different slope positions and soil depths,shedding light on key geomorphological processes.Methods:In this research,the Caesium-137(^(137)Cs)technique was applied to evaluate soil redistribution and soil erosion rates due to the effects of these above-mentioned land-use changes.To achieve this goal,we select a representative area in the Lordegan district,central Iran.^(137)Cs depth distribution profiles were established in four different hillslope positions after converting natural oak forests to rainfed farming.In each hillslope,soil samples from three depths(0–10,10–20,and 20–50 cm)and in four different slope positions(summit,shoulder,backslope,and footslope)were taken in three transects of about 20m away from each other.The activity of ^(137)Cs was determined in all the soil samples(72 soil samples)by a gamma spectrometer.In addition,some physicochemical properties and the magnetic susceptibility(MS)of soil samples were measured.Results:Erosion rates reached 51.1 t·ha^(−1)·yr^(−1) in rainfed farming,whereas in the natural forest,the erosion rate was 9.3 t·ha^(−1)·yr^(−1).Magnetic susceptibility was considerably lower in the cultivated land(χhf=43.5×10^(−8)m^(3)·kg^(−1))than in the natural forest(χhf=55.1×10^(−8)m^(3)·kg^(−1)).The lower soil erosion rate in the natural forest land indicated significantly higher MS in all landform positions except at the summit one,compared to that in the rainfed farming land.The shoulder and summit positions were the most erodible hillslope positions in the natural forest and rainfed farming,respectively.Conclusions:We concluded that land-use change and hillslope positions played a key role in eroding the surface soils in this area.Moreover,land management can influence soil erosion intensity and may both mitigate and amplify soil loss.

Weed Management in Rainfed Upland Rice Fields under Varied Agro-Ecologies in Nigeria

The demand for rice to meet the dietary need in low-income countries is expected to witness an exponential rise as the population increases.Meeting the rice demand domestically has remained challenging due to significant yield loss caused by several biotic and abiotic factors.Among these factors,one of the most important is the high weed pressure that ravages the upland rice ecology.In Nigeria,several independent weed control techniques,such as physical,chemical and cultural methods,have been recommended and adopted for weed control across varying rice upland ecologies.However,outcomes of these approaches when used independently have not consistently led to an increase in yield.There remains an outstanding deficit between the actual yield and the potential rice yield.This review aimed to identify potential research gaps,and quest effective and sustainable weed management strategies in smallholder upland rice farming systems in Nigeria.A critical analysis of studies suggests the potential of sustainable weed management practices if adopted and adapted smartly in different upland ecologies in Nigeria.Competitiveness of upland rice against weeds can be enhanced through strategic integration of weed competitive cultivars,optimum nitrogen application timings(within weed-free periods),uniform plant spacing,and high seeding rates,with conventional herbicide/manual weed control practices.However,such management practices can only be engaged where inputs are supplied on time and the technical know-how is extended to farmers.The review equally highlights potential research gaps for further studies.

APPLICATION OF FUZZY FLEXIBLE CLASSIFICATION IN RAINFED AGRICULTURAL DEMARCATION

The paper, by the flexible classification in fuzzy mathematics, uses precipitation, meantemperature, sunshine duration, dry index (namely evaporation to precipitation in the corre-sponding period) and cumulative temperature≥10°C between March to September asclassifying indices, and classifies the whole region of Ningxia. We have obtained resultswhich are basically in accordance with the previous divisions, but has some differences.

Morphological and Physiological Traits of Assistance in the Selection of High Yielding Varieties of Durum Wheat (<i>Triticum turgidum</i>L. spp. Durum) for the Rainfed Mediterranean Environments of Central Chile

Chile has high potential to produce quality durum wheat;however, it is not self-sufficient. It is necessary to increase durum grain yield in the Mediterranean rainfed areas which are characterized by adverse environmental conditions, mainly, water deficit. The criteria normally used by breeders to select varieties of wheat for these environments are yield under stress and early flowering. The objective of this monograph is to propose that the selection of high yielding genotypes of durum wheat, under Chilean Mediterranean rainfed conditions, be assisted by morphological and physiological traits associated with yield in order to increase its heritability.

Integrated Nutrient Management of Safflower (<i>Carthamus tinctorius</i>L.) under Rainfed Conditions

Optimistic and sustainable supply of soil available nutrients to crop plants enhances productivity. Integrated nutrient management (INM) approach can improve soil fertility on long term basis. The present study was conducted to determine effects of INM on quantitative and qualitative characters of two Safflower (Carthamus tinctorius L.) cultivars “Thori-78 and Leed-00”. Five treatments using different composition of poultry litter, farm yard manure, nitrogen and phosphorous fertilizers with recommended dose as a control measure were replicated thrice in randomized complete design. The results of field trial depicted maximum plant height (174.6 cm), number of heads plant-1 (42.67), number of seeds head-1 (59.0), thousand seed weight (42.26 g), biological yield (3089 Kg·ha-1) and seed yield (455.2 Kg·ha-1) recorded from combined application of FYM @ 2 t·ha-1and Half (N-P) (soil application) (T5) in Genotype “Leed-00” which was statistically different from all other treatments. Thori-78 also showed increase in yield and yield components under the same treatment (T5) i.e.2 t·ha-1 FYM and Half (N-P).No effect of INM was found on fatty acid composition of safflower cultivars. The correlation coefficients illustrated positive and significant association of seed yield with plant height (0.89), number of heads pod-1 (0.86) and number of seeds head-1 (0.83) as a result of application of selected treatment. These results demonstrated the significance of INM in safflower yield improvement under rainfed conditions.

Productivity and Water-Use Efficiency of Sorghum in Rainfed Regime in the Semi-Arid Region of Brazil

Sorghum has become ever more prominent on the global energy scene, with studies in the area becoming extremely important. Agricultural production in the semi-arid region of the Brazilian Northeast is intrinsically dependent on rainfall in the region. However, on both inter- and intra-annual scales, the rainfall regime is quite irregular. The aim of this study was to evaluate the productivity of sorghum grown under a rainfed regime, and the water-use efficiency of crops in the semi-arid region of the northeast of Brazil. The work was carried out in the city of Tabuleiro do Norte in the semi-arid region of the State of Ceará. Mean productivity of the sorghum was 919.42 kg&middot;ha-1, with maximum values being recorded for lot 02 (1032 kg&middot;ha-1), lot 03 (1102 kg&middot;ha-1), lot 04 (2143 kg&middot;ha-1) and lot 12 (1367 kg&middot;ha-1). The greatest value for water-use efficiency, 1.13 m3&middot;kg-1, was found for lot 04, while the smallest value, 4.83 m3&middot;kg-1 was seen in lot 02. It was found that the low productivity of sorghum in a rainfed regime shows that the lack of success in production systems in semi-arid regions is not due to the total amount of rainfall, but rather the spatial and temporal distribution of the rains, as well as the occurrence of hot, dry spells. Furthermore, it can be seen that the best ratio of grain production to water demand shows a strong correlation with the distribution of water throughout the cycle, and not only with the total volume.

Participatory Assessment of the Potential of Traditional Lowland Rainfed Rice Varieties in Lower Casamance

Casamance was perceived as an agricultural granary that had rice potential which could meet the high food demand of Senegal. Given that the rice-growing lands have been degraded due to pedoclimatic variabilities, improved modern varieties are not usually well adapted to the Casamance rice-growing ecosystems. This work aims to contribute to the increase of rice production through varietal diversification and enhancement of cultural heritage. A participatory evaluation of five local farmers’ traditional varieties along with one check was carried out in an experiment laid out in a one-factor complete randomized block design using the six accessions with five replications. ANOVA followed by a 5% mean comparison Tukey test and the Kendall Rate were performed with IBM SPSS Statistics software. The result showed very significant varietal differences for leaf blade of the penultimate leaves, 100-grains weight, panicle length, growth cycle, plant height, ramification of secondary branching of the spikelets, resistance to lodging and threshing facility (p ≤ 0.005). However, traits including flag leaf, tiller numbers, sterile tillers number, panicle numbers, panicle yield, and grain yield did not show a significant difference (p ≥ 0.06) among varieties. Thus, based on some of these characteristics, farmers selected their most preferred rice varieties or accessions. The most important characteristics were tillering ability, lodging resistance and fertility rate. Koussik Emandiouck selected by farmers as the best variety, had a high grain yield (4.9 t∙ha-1), higher lodging resistance (9), and higher fertility rate (80.53%). Koussik Emandiouck, Koufekeny and Awandiaho varieties were the most preferred by farmers.

Effects of puddling on percolation and rice yields in rainfed lowland paddy cultivation: Case study in Khammouane province, central Laos

We investigated the effects of puddling on percolation and rice yields in rainfed lowland paddy cultivation. We selected a study village in Khammouane province, central Laos, and set up non-puddling and puddling plots from high to low positions. Even when puddling was conducted carefully, the ponding water in the plots disappeared in the case of little rainfall. Further, percolatifons during the later periods of rice growth increased drastically. Therefore, it is difficult to overcome drought stresses only by conducting puddling. We also compared the water conditions in the non-puddling and puddling plots. In the puddling plots at high position and low position along a stream, the number of days without ponding water in the puddling plots was less than that in the non-puddling field in July, suggesting the possibility of a different transplanting date. We tried to estimate the effects of transplanting date on the rice yields and found that transplanting 15 days earlier leads to an increase of 0.5 t/ha in the rice yields. Moreover, the profits from the increased yields exceed the puddling costs considerably, leading to a definite increase in income. Because the transplanting date has no effects in the fields with high ground water, puddling is effective in paddy fields where ponding does not occur to a significant degree.

Field Assessment of Soil Water Storage and Actual Evapotranspiration of Rainfed Maize (<i>Zea mays</i>L.) Genotypes in a Coastal Savannah Environment

A field experiment was carried out in a coastal savannah agro-ecological zone of Ghana to assess the dynamics of stored soil water and actual evapotranspiration (AET) of three maize genotypes (Obatanpa, Mamaba, and Golden Crystal) grown under rainfed conditions. Access tubes were installed to a depth of 120 cm for soil water content monitoring using a neutron probe meter. The soil water balance model of plant root zone was used to estimate AET at different crop growth stages. On average, the rate of AET for Obatanpa, Mamaba, and Golden Crystal maize genotypes were estimated as 4.32, 4.46, and 3.72 mm·day–1, respectively, for the major cropping season as against corresponding values of 3.88, 4.00 and 3.72 mm day–1 for the minor cropping season. Mamaba had higher values of AET from 42 DAE (days after emergence) to 84 DAE during the minor cropping season while it had low AET values during the major cropping season. The positive balance in stored soil water in the root zone of Obatanpa was the highest from 42 DAE to 84 DAE followed by Mamaba and Golden Crystal during the major cropping season. Mamaba, on the other hand, had the highest AET from 70 DAE to 84 DAE. Obatanpa used 55.6% of stored soil water for AET, which was the highest among the maize genotypes during the major cropping season. Golden Crystal and Mamaba followed with 53.3% and 51.5%. For the minor cropping season, 48.5% of stored soil water was used by Mamaba for AET, followed by Obatanpa, (46.4%) and Golden Crystal (43.2%). A strong positive significant (p ≤ 0.05) linear correlation existed between AET and precipitation with the coefficient of determination (R2) being 69.2 for Obatanpa, 88.5 for Mamaba and 82.8 for Golden Crystal for the major cropping season. Higher R2 values (98.0, for Obatanpa, 94.1 for Mamaba and 98.9 for Golden Crystal) were, however, obtained for the minor cropping season. Additionally, a strong linear relationship was found between AET and precipitation, suggesting the need to formulate strategies for enhancing effective use of precipitation in sustained rainfed maize production.

Modeling crop land soil moisture and impacts of supplimental irrigaiton in a rainfed region of Bangladesh

A robust water balance model has been tested for predicting soil moisture levels and supplemental irrigation requirement of a rainfed region of Bangladesh. The predictions were used for improving the understanding of the impacts of rainwater harvesting on rainfed agriculture. The climate data (i.e., rainfall, temperature, evaporation, and evapotranspiration) were used as inputs for predicting the variations in soil moisture. Soil moisture levels under rainfed and supplementary irrigation conditions were compared. Results showed that rainwater harvesting i.e., rain water storage tanks during rainy seasons can be potentially useful for storing rainwater, which can be utilized for enhancing crop land soil moisture during dry seasons for enhancing crop yield. The study presented here will be useful for improving and disseminating rainwater harvesting approaches for enhancing water availability in rainfed regions.

Rainfed Crops Forecasting in the Semi-arid Region under Scenarios of Rainfall Instability in Ceará, Brazil

This paper aimed to analyze the projections of rainfed crops(rice,beans,cassava and corn)in the semi-arid region under scenarios of rainfall instability in Ceará,in the period from 1945 to 2020.The data were collected from the Meteorology and Water Resources Foundation of Ceará(FUNCEME)and the Brazilian Institute of Geography and Statistics(IBGE),through the IBGE System of Automatic Recovery(SIDRA),which provides data on Municipal Agricultural Production(PAM-2020).The rainfall periods were organized in three categories:drought,normal and rainy periods.This was done using the historical average and standard deviation of rainfall from 1945 to 2020.The projections of production variables were made through the Autoregressive Integrated Moving Average(ARIMA)methodology.The results show that the rainfall distribution in CearáState between 1945 and 2020 was quite unstable.The coefficient of variation(CV)of the rainfall periods ranges between 33%in normal period and 54%in the drought period.Based on the results,it is observed that the general hypothesis of the article was confirmed,showing that rains have an impact on rainfed agricultural production in Cearáin the variables:harvested area,productivity and prices of rice,beans,corn and cassava crops.The results also showed that the cassava crop presents favorable results in relation to the interference of rainfall,suggesting that the crop is better adapted to the climatic adversities of the region.

Potential for Growing <i>Salvia hispanica</i>L., Areas under Rainfed Conditions in Mexico

The Salvia hispanica L. is an endemic species Mexican plant, which relevance relies upon its properties as a natural source of omega 3 (α-linolenic acid), soluble and insoluble fibers, proteins, plus some other significant nutritional components. Due to the growing relevance generated by this crop, it became necessary to characterize its physical environment, as well as the natural factors related with its cultivation nationwide, aiming to find those most suitable for its production under rainfed conditions, looking forward to provide the basis to make a decision regarding where to target the agriculture promotion of such cropland. The software used for data process and analysis was the Arc/View 3.3 version. Thus, the crop requirements were recognized in order to analyze those most suitable for chia development in each one of its selected variables in the study hereby. The regionalization and mapping aimed to detect both the optimal and suboptimal potential areas for such crop were carried out, afterwards. It was finally determined that Mexico holds a total of 2,512,359 hectares with an optimal or high cultivation potential, whereas the areas with a medium or suboptimal potential are close to 3,658,089 hectares, which can be set under rainfed conditions.

The Potential of Hydro-Climate Forecast Strategies in Sustaining Agricultural Productivity amongst Rainfed Farmers in West Africa: A Review

Several studies have reported a significant yearly decrease in forest cover globally, using satellite images. This is especially true in West Africa, where rapid urbanisation acerbates the problem, and both of these changes lead to alterations in rainfall regime and other changes in climatic parameters. Several studies reveal that adaptation which reduces vulnerability to adverse climatic variation effects is the key to developing resilience against climate change. In this region, over 90% of farmers are engaged in small-scale rainfed crop cultivation and rely on their own weather perception, instincts and what they observe from the surrounding biota (flora and fauna) to forecast the weather and plan their agricultural activities. The pressing nature of the problem of climate variability in Africa had provoked a lot of research into developing and testing several adaptation strategies to control the situation. Various strategies to improve and localize global, regional and national climate services (Local Forecast, Scientific Forecast and Integrated Forecast) needed by the farmers are being developed to build resilience against climate change. This review illustrates the situation in Ghana and identifies various forecast strategies developed to mitigate the adverse effects of climate variability on agricultural productivity. These mitigation methods include the development of climate services to provide users with forecast information in order to make climate-smart decisions to minimize the risk.

The Effects of Different Levels of Nitrogen on Yield and Yield Components of Rainfed Wheat in Two Regions of North Khorasan

To study the effects of different levels of nitrogen fertilizer on yield and yield components of cultivars of rainfed wheat a study was done in the crop year 2012-2013 as factorial in a randomized complete block design with 3 replications, in 2 research stations of Kohne Kand city in Bojnord and Shirvan dryland research station. The treatments of study contain cultivars of wheat in 4 levels (Rasad, Sabalan, Cross Sabalan and Azar 2) and 4 levels of nitrogen fertilizer (75, 50, 25 and 0 kilograms nitrogen per hectare). The results showed that the yield in Shirvan was significantly higher than that in Bojnoord. Moreover, the impact of cultivar and nitrogen on yield and yield components was significant in both regions and among different cultivars Azar 2 has the highest yield in both regions and the lowest yield was for cross Sabalsn in Shirvan and Sabalan in Bojnoord. Furthermore, yield increased by increasing the nitrogen in both regions but there was no significant difference between levels 50 and 75 kilograms per hectare. Among yield components except the number of spikes per square meter, others had a high correlation with yield.

Climate Based Risk Assessment for Maize Producing Areas in Rainfed Agriculture in Mexico

Rainfed areas in Mexico accounts for 14 million hectares where around 23 million people live and are located in places where there is a little climatic information. The severe drought that has impacted northern Mexico in the past several years as well as other parts of the country, has forced decision takers to look for improved tools and procedures to prevent and to cope with this natural hazard. For this paper, the methodology of the Food and Agricultural Organization of the United Nations (FAO) for estimating water balance variables was modified to provide crop yield estimations under rainfed agriculture in maize producer states of Mexico. The water balance accounts for the daily variation of soil water content having main input rainfall (Pp) and main output crop evapotranspiration (Eta). The algorithm computes crop yield using two distinctive approaches: 1) one based on surplus/deficit functions for each crop considered and 2) yield estimations based on soil water balance and water function productions of the crop being analyzed. For computing water balance and crop yields, a computer model is built that incorporates the FAO method for water balance (MODEL SICTOD: Computational System for Decision Taking, acronym in Spanish) which stochastically generate precipitation based on wet/dry transition probabilities using a first order Markov chain scheme. Maps of average crop yields were obtained after interpolating model outcomes for the main maize producer states of Mexico: Jalisco, Michoacan, Guerrero, Puebla Oaxaca and Chiapas. Different planting dates were analyzed, early (90 days of length period), intermediate (120 days of length period) and late (150 days of length period). Crop yield variability correlates to the transition probability on having a wet day following a dry day. Results have shown high yield variation and probability of crop yield failure and climatic risk follows a distinctive pattern according to planting date and rainfall occurrence. The approach used is of great support for decision taking processes.

Nitrogen and phosphorus fertilization leads to soil arbuscular mycorrhizal fungal diversity changes and rainfed crop yield increase on the Loess Plateau of China:A 37-year study

More than 80%of plants form mutualistic symbiotic relationships with arbuscular mycorrhizal fungi(AMF),and the application of fertilizers,such as nitrogen(N)and phosphorus(P)fertilizers,is a common agricultural management practice to improve crop yield and quality.However,the potential effects of long-term N and P fertilization on the AMF community in the rainfed agricultural system of the Loess Plateau of China are still not well understood.In this study,a long-term field experiment was conducted based on orthogonal design,with three N levels(0,90,and 180 kg ha^(-1)year^(-1))and three P levels(0,90,and 180 kg ha^(-1)year^(-1))for wheat fertilization.Changes in AMF community and correlations between AMF community composition,soil environmental factors,and wheat yield component traits were analyzed using traditional biochemical methods and high-throughput sequencing technology.The results showed that long-term N and P addition had a significant effect on the AMF community structure and composition.Nitrogen application alone significantly reduced the richness and diversity of AMF community,whereas the combined application of N and P significantly increased the richness and diversity of AMF community.The AMF community was driven mainly by soil available P,total P,and pH.There was a significant positive correlation between Glomus abundance and wheat yield and a significant negative correlation between Paraglomus abundance and wheat yield.Long-term N and P addition directly increased crop yield and affected yield indirectly by influencing soil chemical properties and the AMF community.Combined application of N and P both at90 kg ha^(-1)year^(-1)could improve the ecological and physiological functions of the AMF community and benefit the sustainable development of rainfed agriculture.

Economic modeling of mechanized and semi-mechanized rainfed wheat production systems using multiple linear regression model

Mathematical modeling of economic indices is a challenging topic in crop production systems.The present study aimed to model the economic indices of mechanized and semimechanized rainfed wheat production systems using various multiple linear regression models.The study area was Behshahr County located in the east of Mazandaran Province,Northern Iran.The statistical population included all wheat producers in Behshahr County in 2016/17 crop year.Five input variables were human labor,machinery,diesel fuel,chemical(chemical fertilizers and chemical pesticides)costs,and the income was considered to be the output.The results showed that the cost of wheat production in the semimechanized system was higher than that of the mechanized system.In both systems,the highest cost was related to agricultural machinery input.Moreover,seed cost was lower in the mechanized system than that of the semi-mechanized system.The net return indicator was 993.68$ha1 and 626.71$ha1 for the mechanized and semi-mechanized systems,respectively.The average benefit to cost ratio was 3.46 and 2.40 for the mechanized and semi-mechanized systems,respectively,demonstrating the greater profitability of the mechanized system.The results of the evaluation of five types of regression models including the Cobb-Douglas,linear,2FI,quadratic and pure-quadratic for the mechanized and semi-mechanized production systems indicated that in the developed Cobb-Douglas model,the R2-value was higher than that of the quadratic model while RMSE and MAPE of the quadratic model were determined to be smaller than that of the Cobb-Douglas model.Therefore,the best model to investigate the relationship between input costs and the income of wheat production in both mechanized and semi-mechanized systems was the quadratic model.