Yield gaps and ecological footprints of potato production systems in Chile

In Chile, potatoes are grown in a wide range of ecological zones and levels of technology resulting in wide ranges of crop management and yields. The aim of the present study was to assess yield gaps, resource use efficiencies and foot-printing in different potato cropping zones between 18 and 53° South considering early and late crops, small and large holdings (>10 ha/year) and ware and seed potato crops. Two mathematical tools were used to generate data for comparisons: the light interception and utilization simulator for potato crops (LINTUL-Potato) to calculate potential yields and water need of each system and the Cool Farm Tool – Potato (CFT) to calculate the amount of CO2 associated with the production of 1 ton of potato. Meteorological data for LINTUL-Potato came from official services, and data needed to complete the CFT came from a survey carried out for the 10 sites yielding amounts of inputs and number of operations, potato yields and planting and harvesting dates. The survey yielded 20 cropping systems with an average yield of 31 t ha−1. Yields were related to daily growth rate and not to the length of the growing season. Considerable variation was found in resource-use efficiency and CO2 emission. It was concluded that large farms show a lower land footprint than small farms due to a higher technological level, but while applying more water and fertilizer, they result in higher water and CO2 footprints. Late crops may fetch higher off-season prices but have higher land, water and CO2 footprints. The most suitable potato production systems are the rain-fed summer crops in the South with the lowest footprints. The highest footprints have the irrigated winter crops in the centre of Chile. The subsistence high altitude Andean crop in the utmost North has the highest land footprint but the lowest CO2 emission. The description,analysis and benchmarking of the potato production systems in Chile allow strategies for improving footprints and profitability and yields information about future investments in research, development and production of the crop.http://link.springer.com/journal/11540hb201

Potato crop response to genotype and environment in a subtropical highland agro-ecology

Potato response to environment, planting date and genotype was studied for different agro-ecological zones in Lesotho. Field experiments were conducted at four different sites with altitudes ranging from 1,655 to 2,250 m above sea level during the 2010/2011 and 2011/2012 summer growing seasons. Treatments consisted of three cultivars that varied in maturity type, two planting dates and four sites differing in altitude and weather patterns. Various plant parts were measured periodically. To understand and quantify the influence of abiotic factors that determine and limit yields, the LINTUL crop growth model was employed which simulated potential yields for the different agro-ecological zones using weather data collected per site during the study period. Observed actual crop yields were compared with model simulations to determine the yield gap. Model simulations helped to improve our understanding of yield limitations to further expand potato production in subtropical highlands, with emphasis on increasing production through increased yields rather than increased area. Substantial variation in yield between planting date, cultivar and site were observed. Average tuber dry matter (DM) yields for the highest yielding season were above 7.5 t DM ha−1 or over 37.5 t ha−1 fresh tuber yield. The lowest yield obtained was 2.39 t DM ha−1 or 12 t ha−1 fresh tuber yield for cultivar Vanderplank in the 2011/2012 growing season at the site with the lowest altitude. Modelled potential tuber yields were 9–14 t DM ha−1 or 45–70 t ha−1 fresh yield. Drought stress frequently resulted in lower radiation use efficiencies and to a lesser degree harvest indices, which reduced tuber yield. The site with the lowest altitude and highest temperatures had the lowest yields, while the site with the highest altitude had the highest yields. Later maturing cultivars yielded more than earlier maturing ones at all sites. It is concluded that the risk of low yields in rain-fed subtropical highlands can be minimised by planting late cultivars at the highest areas possible as early as the risks of late frosts permit.http://link.springer.com/journal/11540hb201

Climate change and potato production in contrasting South African agro-ecosystems 2 : Assessing risks and opportunities of adaptation strategies

This study aims to assess the risks and opportunities posed by climate change to potato growers in South Africa and to evaluate adaptation measures in the form of changes in planting time growers could adopt to optimise land and water use efficiencies in potato, using a climate model of past, present-day and future climate over southern Africa and the LINTUL crop growth model. This was done for distinct agro-ecosystems in South Africa: the southern Mediterranean area where potato still is grown year round with a doubling of the number of hot days between 1960 and 2050, the Eastern Free State with summer crops only and Limpopo with currently autumn, winter and spring crops where the number of hot days increases sevenfold and in future the crop will mainly be grown in winter. A benefit here will be a drastic reduction of frost days from 0.9 days per winter to 0. Potato crops in the agroecosystems will benefit considerably from increased CO2 levels such as increased tuber yield and reduced water use by the crop, if planting is shifted to appropriate times of the year. When the crop is grown in hot periods, however, these benefits are counteracted by an increased incidence of heat stress and increased evapotranspiration, leading in some instances to considerably lower yields and water use efficiencies. Therefore year-round total production at the Sandveld stabilizes at around 140 Mgha−1 (yield reduction in summer and yield increase in winter), increases by about 30% in the Free State and stays at about 95 tha−1 at Limpopo where yieldPotatoes South Africa and the Netherlands Ministry of Economy, Agriculture and Innovation Agriculturehttp://link.springer.com/journal/11540hb201

A quantitative framework for evaluating the sustainability of Irish potato cropping systems after the landmark agrarian reform in Zimbabwe

Frameworks to evaluate the sustainability of cropping systems in developing countries are scarce. This study proposes a framework to select easily quantifiable indicators that can be used to assess and communicate the sustainability of cropping systems in developing countries. The widely accepted social, economic and environmental dimensions of sustainability were covered using predefined criteria from which the indicators were then drawn. An initial list of indicators was established based on literature review and expert opinion, and through filtering reduced to 16 core indicators. Using the case of Irish potatobased cropping systems, a grower survey was conducted to collect data on production practices in four different cropping systems. The survey data were then used to calculate the sustainability indicators expressed as resource use efficiencies based on actual potato yields. The survey data also served as input into the Cool Farm Tool – Potato model to estimate greenhouse gas emissions from farm operations involved in potato production. With the help of local agricultural extension officers, focus group discussions were held with farmers of each production system to decide on sustainable and unsustainable indicator threshold levels. The participatory nature of the framework involving farmers and local extension officers secured buy-in from key stakeholders important for operationalization, monitoring and evaluation.The Wageningen University and Research Centre Sandwich PhD programme, with additional funding from the Chinhoyi University of Technology for field data collection in Zimbabwe.http://www.ippublishing.com/oa.htmam2016Plant Production and Soil Scienc

Comparative analysis of Irish potato (Solanum tuberosum L.) production in the farming sectors that emerged from Zimbabwe’s radical land reform of 2000

Irish potato production in Zimbabwe can be traced back to the early 1900s. Large-scale commercial farmers dominated production till the early 2000s. Potato is the most important horticultural crop and has been declared a strategic national food security crop in 2012. In 2000, the Fast Track Land Reform Programme completely restructured commercial agriculture and potato farming. A product of the agrarian reforms, the A2- and A1- resettlement growers, started growing potato. The A1 resettlement model has individually owned cropping land and shared grazing, while A2 resettlement comprises of self-contained farm units. A survey was conducted to characterise potato growers, mainly to understand the current potato production systems and assess the impact of the landmark reform programme on potato farming. Four production systems, Large-scale commercial, Communal area, A2 resettlement and A1 resettlement, were identified, and two main growing agro-ecological zones, the Highveld and Eastern Nyanga Highlands. In 1961–2013, significant positive trends for annual planted area, average yield and total production were observed. In terms of yield, Zimbabwe is fourth in southern Africa with average yield of 17 t ha-1 in the 2009–2013 period. Large-scale commercial and A2 resettlement systems were well-mechanized and growers owned large land holdings ranging from an average of 165–1,600 ha and 31– 390 ha across the different areas respectively, with average potato areas of 11 and 8 ha, respectively. A1 resettlement and Communal area growers owned an average of 4 and 3 ha cropping area, respectively, with average potato areas of 0.4 and 1.1 ha, respectively. Input use was significantly different among the production systems. High synthetic fertiliser and biocides use was observed.This research was conducted under the Wageningen University and Research Centre Sandwich PhD programme of the Netherlands (Grant number: 318330), with additional funding from the Chinhoyi University of Technology, Zimbabwe (Grant number: RB2240) for field data collection in Zimbabwe.http://link.springer.com/journal/115402018-03-12hb2017Plant Production and Soil Scienc

Forecasting yield and tuber size of processing potatoes in South Africa using the LINTUL-Potato-DSS model

The LINTUL-Potato-DSS model uses the linear relationship between radiation intercepted by the crop and radiation-use efficiency (RUE), to calculate dry matter production. The model was developed into a yield forecasting system for processing potatoes based on long-term and actual weather and crop data. The model outcome (Attainable yield, Yatt) was compared to actual yields (Yact) of a summer crop in South Africa and the ratio Yact to Yatt was used for forecasting yield in winter crops. Results showed that accurate forecasts (<20% variation between the actual and forecasted values) could be produced already early in the growing season, and that for the cultivar Innovator, actual and forecasted yields were well correlated (r = 0.797). Forecasted and observed yields at harvest were not significantly different at the 5% level, P = 0.637 (t test). Forecasts of tuber number using LINTUL-Potato-DSS were not accurate in the present study and further research is needed on this aspect. It is concluded that the model is a valuable management tool that can be used to produce accurate forecasts of tuber yield from as early as 8 weeks before the final harvest. Since the model was tested with only one cultivar grown in three different growing regions of South Africa, further evaluation using different cultivars and localities is recommended.http://link.springer.com/journal/115402017-09-30hb2016Plant and Soil Science

Climate change and potato production in contrasting South African agro-ecosystems 1. Effects on land and water use efficiencies

Explorations of the impact of climate change on potential potato yields were obtained by downscaling the projections of six different coupled climate models to high spatial resolution over southern Africa. The simulations of daily maximum and minimum temperatures, precipitation, wind speed, and solar radiation were used as input to run the crop growth model LINTUL-Potato. Pixels representative for potato growing areas were selected for four globally occurring agro-ecosystems: rainy and dry winter and summer crops. The simulated inter-annual variability is much greater for rainfall than for temperature. Reference evapotranspiration and radiation are projected to hardly decline over the 90-year period, whilst temperatures are projected to rise significantly by about 1.9 °C. From literature, it was found that radiation use efficiency of potato increased with elevated CO2 concentrations by almost 0.002 gMJ−1ppm−1. This ratio was used to calculate the CO2 effect on yields between 1960 and 2050, when CO2 concentration increases from 315 to 550 ppm.Within this range, evapotranspiration by the potato crop was reduced by about 13% according to literature. Simulated yield increase was strongest in the Mediterraneantype winter crop (+37%) and least under Mediterranean summer (+12%) and relatively warm winter conditions (+14%) closer to the equator. Water use efficiency also increased most in the cool rainy Mediterranean winter (+45%) and least so in the winter crop closer to the equator (+14%). It is concluded from the simulations that for all four agro-ecosystems possible negative effects of rising temperatures and reduced availability of water for potato are more than compensated for by the positive effect of increased CO2 levels on water use efficiency and crop productivity.Potatoes South Africa and The Netherlands Ministry of Economic Affairshttp://link.springer.com/journal/11540hb201

Resource use efficiencies as indicators of ecological sustainability in potato production : a South African case study

Potato, the most important vegetable crop in South Africa, is produced in many distinct geographical regions differing in climate, soils, production seasons and management practices and access to markets. These differences affect the amount of input resources required to produce potatoes as well as yields and crop value, and therefore the use efficiencies of land, water, nutrients, seed and energy. Resource use efficiencies affect the ecological and financial sustainability of potato production in this region, which has in general less favourable potato growing conditions than north-western Europe and the U.S.A., where high resource use efficiencies are usually recorded. This study aimed to assess and benchmark South African potato production regions, representing a wide range of growing conditions, regarding their use of input resources and to identify resource-intensive practices, which may suggest inefficient use of inputs. Surveys were conducted in 2013 and 2014 by interviewing growers in all production regions, to provide data on resource use efficiencies. Quantitative modelling approaches were applied to calculate carbon footprints as a proxy of energy use efficiency, potential crop yields and irrigation needs for each region. Variability in the gap between potential and actual yield was used to identify yield limiting factors. Actual yields achieved were on average 60% of the potential yield, suggesting fairly efficient use of available production factors. Water, seed and nutrient use efficiencies differed widely between and within regions and were not directly proportional to water requirements and yields achieved. Fertilizers (34%) and irrigation (30%) were the greatest contributors to energy use in potato crop production. Energy required to pump water was strongly related to the amount of irrigation applied, pumping depth and distance. Long distance travel of produce to retail points contributed substantially to energy use. Significant improvements in efficiencies are possible by improving management practices. Analysis of the variability in resource use efficiencies between farms and regions provided production sustainability indicators that can assist growers in identifying inefficient practices and yield limiting factors. These can be addressed through the use of decision support systems, such as irrigation scheduling tools, to improve resource use efficiencies and the sustainability of production, not only for the production efficiency of the specific study area, but also for the economic efficiency of potato production anywhere else.This work was financially supported by Potatoes South Africa.http://www.elsevier.com/locate/fcr2017-12-31hb2016Plant Production and Soil Scienc

Grower perceptions of biotic and abiotic risks of potato production in South Africa

Growers’ surveys took place in all sixteen potato growing regions of South Africa in 2013 and 2014. The agro-ecological climate of these regions is diverse and potato is produced in rainy or dry seasons, in winter or summer seasons, or year round. Growers were asked how often in ten years crops suffered more than 25% yield losses due to extreme weather events related to precipitation events such as hail, floods and droughts, and to temperature-related events such as frost and heat waves. Simultaneously they were asked their opinion about occurrence and severity of diseases caused by potato viruses, fungi and bacteria and pests such as nematodes, tuber moths, aphids and leaf miners. Weather related hazards resulted in losses over 25% virtually each year in the Gauteng growing region due to hail, frosts and floods; losses occurred less than once every five years, for example due to extremely high temperatures, in the Sandveld area where growers take a risk by producing potatoes in hot summers. Regarding the biotic factors, every pest or pathogen assessed was reported to occur on at least one farm in each growing region. Countrywide the lowest frequency of 50% was recorded for powdery scab whereas the insects tuber moths, leaf miners and aphids were reported most frequently, by between 88% and 98% of the growers. The complex of silver scurf and black dot resulted in the greatest yield losses in all growing regions, followed closely by tuber moth, early blight and the blackleg / soft rot disease complex. Yield losses due to potato virus Y, potato leaf roll virus and aphids were not reported as being very severe. When the growers’ perceptions of severity of biotic factors were accumulated, significant differences between the regions appeared, with the Eastern Cape most prone with an accumulated score of 700 due to an array of pests and diseases, and the North- West with a score of only 50 mainly attributed to root knot nematodes. Growers were also asked how frequently biocides were applied to potato to control soil-borne organisms (nematicide and seed treatment), foliar fungi or insects. There were no significant correlations between frequency of biocide applications and severity of the disease as reflected in yield losses, most likely because growers use biocide applications as insurance against pests and diseases. This is common among crop farmers around the world. Although potato production in South Africa appears to carry more risks than production elsewhere, South African commercial potato growers are economically competitive when compared to growers in other areas of the globe, with comparable planting conditions and risks.http://www.elsevier.com/locate/cropro2017-06-30hb2016Plant Production and Soil SciencePlant Scienc

A robust potato model : LINTUL-POTATO-DSS

In 1994, LINTUL-POTATO was published, a comprehensive model of potato development and growth. The mechanistic model simulated early crop processes (emergence and leaf expansion) and light interception until extinction, through leaf layers. Photosynthesis and respiration in a previous crop growth model—SUCROS— were substituted by a temperature-dependent light use efficiency. Leaf senescence at initial crop stages was simulated by allowing a longevity per daily leaf class formed, and crop senescence started when all daily dry matter production was allocated to the tubers, leaving none for the foliage. The model performed well in, e.g., ideotyping studies. For other studies such as benchmarking production environments, agroecological zoning, climatic hazards, climate change, and yield gap analysis, the need was felt to develop from the original LINTUL-POTATO, a derivative LINTULPOTATO- DSS with fewer equations—reducing the potential sources of error in calculations— and fewer parameters. This reduces the number of input parameters as well as the amount of data required that for many reasons are not available or not reliable. In LINTUL-POTATO-DSS calculating potential yields, initial crop development depends on a fixed temperature sum for ground cover development from 0% at emergence to 100%. Light use efficiency is temperature dependent. Dry matter distribution to the tubers starts at tuber initiation and linearly increases up to a fixed harvest index which is reached at crop end. Crop end is input of the model: it is assumed that the crop cycle determined by maturity matches the length of the available frost-free and or heat-free cropping season. LINTUL-POTATO-DSS includes novel calculations to explore tuber quality characteristics such as tuber size distribution and dry matter concentration depending on crop environment and management.http://link.springer.com/journal/11540am201