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

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

Analysis of seed and ware potato production systems and yield constraints in Argentina

The aim of this thesis is to analyze the seed and ware potato production systems in Argentina and their possible yield constraints in order to develop specific strategies to increase seed quality and tuber yield.This thesis starts with a survey of the actual potato production systems in Argentina carried out during 1994/95 and updated in 1999. Argentina currently produces well over 2 million tonnes of potatoes per annum on just over 100,000 ha. The survey also describes the acreage and production in different areas, agro-ecological conditions in each of these areas, yield constraints and perspectives for yield improvement. It also presents data on area, production and yield for each growing season and characterizes the seed and ware production systems in these areas in terms of weather based on long-term meteorological data and soils based on digitized soil maps for the whole country. In each of these areas yield determining, yield limiting and yield reducing factors are identified. High temperatures during planting and harvest time are the main yield determining factors as they affect crop growth and/or seed and ware quality. Also high temperatures during storage may be detrimental to the quality of stored seed or ware. Water and nutrient supply and physiological age of the seed are the main yield limiting factors in different seed and ware potato areas. Virus diseases, early ( Alternaria solani ) and late ( Phytophthora infestans ) blight are the main yield reducing factors in some areas. Strategies to solve problems of improper physiological age and virus infection are analyzed later in this thesis in order to obtain further improvements in yield and quality.A simulation study at national and regional levels (1) characterizes agro-ecological zones for potato production; (2) establishes potential growing seasons; (3) estimates the potential yields of the crop in these zones and seasons, and, at a regional level, also for different planting dates; and (4) discusses how these results match with reality and how they can be used for the benefit of the potato industry.Two models are used in these studies; the SUBSTOR-POTATO model for yield prediction and the LINTUL-POTATO model for a yield gap analysis.The SUBSTOR-POTATO model is calibrated and validated using Argentinian data sets from experimental results from different sites and years. Cultivar-specific coefficients are obtained during calibration and validation is based on several independent sets of field data, including cvs Huinkul, Kennebec, Mailén and Spunta. The observed and simulated values show good agreement within normal ranges of tuber yields. The particular behaviour of the input parameter maturity date is also considered, in order to properly assess tuber yield. A genetic coefficient for the duration of tuber bulking needs to be included in the model in order to obtain proper yield values under Argentinian conditions.A yield gap analysis is carried out with data from five different agro-ecological potato growing zones by comparing potential yield data obtained with the LINTUL-POTATO simulation model with the actual and attainable yields. This analysis is used to identify the possible factors determining, limiting or reducing yield in each of the areas considered and to analyse options for further yield improvement. Special emphasis is put on the yield limiting effect of the physiological age of seed tubers, water and nutrient management, and the quality and yield reducing effects of virus diseases. Results show, for the regions studied, that the actual yield is still far below the attainable and potential yields, due to suboptimal light interception by the foliage, poor seed quality, and lack of early ( Alternaria solani ) and late blight ( Phytophthora infestans ) control.Based on these results a physiological age index (PAI) that combines both the effect of chronological and physiological age of seed tubers is developed. PAI calculation is based on different key-dates of the life cycle of a seed tuber, which are easy to assess, i.e. the haulm killing date of the seed crop (T 0 ) and the end of the incubation period of seed tubers, measured under standard conditons. The PAI is: T 1 /T 2 , where T 1 is the time from haulm killing date (T 0 ) to possible planting date and T 2 the time from T 0 to the end of the incubation period. The PAI expresses physiological ageing of seed potato tubers within a range from 0 for physiologically young to 1 for old tubers. To test the PAI, existing data are re-evaluated and re-elaborated and specific experiments on the effects of seed origin and storage conditions for different cultivars have been performed during 1994/99. The effects of seed origin, seed supply and seed flow are also analyzed in terms of the effects of the physiological age of seed tubers on subsequent crop performance and yield. A survey on seed supply and seed flow evaluates the effects of different origins and storage systems upon crop growth and yield under practical conditions. The effects of physiological age on yield can be mainly attributed to improved light interception. PAI correlates well with the proportion of potential yield attained in different planting seasons.Different strategies may help to overcome the effect of yield limiting and quality and yield reducing factors, such as the physiological age of seed tubers and virus diseases. Application of plant growth regulators such as gibberellic acid and benzyl aminopurine modifies the effect of the physiological age of seed tubers on the progeny crops. Especially benzyl aminopurine is promising in overcoming the negative effect of old seed tubers on crop growth and yield. The development of a seed production system on the isolated island of Tierra del Fuego in the southern part of the country proves to be a sound strategy to multiply basic seed or to carry out initial multiplications in breeding programmes. Presence of nematodes, aphids and virus proves to be very low and growing and storage conditions allow the production of young seed. Seed yields and physiological quality are acceptable, and the seed is very healthy, with virtually no viral, fungal or bacterial infections.The study shows how a highly complex potato production system, like the Argentinian one, can be surveyed and analyzed. The survey work is complemented with the use of a Geographic Information System and simulation model approaches which improve our understanding of the possibilities for increasing future crop production by expanding the area cropped with potatoes and/or yield. The use of a yield gap analysis is also a useful and comprehensive tool to identify and rank yield defining, yield limiting and yield reducing factors for those agro-ecological zones where the potato is currently grown. With these procedures, the physiological age of seed tubers and virus diseases are identified as the most relevant factors limiting and reducing yield. Specific strategies are developed to counteract their limiting and reducing effects upon seed quality and tuber yield.The approach of this thesis does not only applied for the specific situation of the potato crop in Argentina, but this framework could be successfully applied to other crops or production systems elsewhere.</p

Yield components and grain yield in two Argentinian wheat (Triticum aestivum L.) cultivars differing in plant height under different nitrogen supply

El objetivo de este trabajo fue estudiar las relaciones entre el rendimiento en grano y sus componentes en dos cultivares, uno de ellos con germoplasma tradicional y el otro mejicano, cuando éstos eran cultivados con distinta disponibilidadde N a lo largo del ciclo de cultivo. Klein Toledo y La Paz INTA, cultivares de altura standard y semi-enano, respectivamente, fueron cultivados bajo alta (H) y baja (L) disponibilidad de N, modificada al estadio de: número máximo de flores.La baja disponibilidad de N al inicio del ciclo de cultivo redujo severamente  el número de espiguillas/espiga-1 y el peso seco/planta-1 siendo este efecto mucho mayor en el cultivar semi-en no, donde se produjeron reducciones del 34, 42 y 70% para estos parámetros, respectivamente. Al estado de número máximo de flores la menor disponibilidad de N produjo reducciones en todos los parámetros evaluados, a excepción del número de flores/espiguilla-1,que parece ser menos sensible a limitaciones de tipo ambiental que otros parámetros. Las reducciones en el número de sitios potenciales para formar grano (número de espiguillas/spiga-1 x número de flores -espiguilla-1, al estado de número máximo de flores, debido a disminuciones en el número de espiguillas,no fueron modificadas por el posterior agregado de N. De allí que, a la cosecha, el número de granos/espiga-1 haya sido marcadamente afectado, aunque no hubo diferencias entre los cultivares.Por otra parte, también se demostró que, en ambos cultivares la asimilación de N continúa aun luego de antesis, probablemente por una mayor retención de la capacidad funcional de las raíces. Cuando el objetivo del cultivo es obtener altos rendimientos, y no existen otros factores capaces de limitar el mismo, la disponibilidad temprana de N es clave para lograr resultados favorables

Analysis of a complex crop production system in interdependent agro-ecological zones : a methodological approach of potato in Argentina

This paper shows how a highly complex potato production system, like the Argentinian one, can be surveyed and analysed. A survey was complemented with the use of a Geographic Information System and a simulation model approach which improves the understanding of the possibilities for increasing future crop production by expanding the area cropped with potatoes and/or the yield. A yield gap analysis was also a useful and comprehensive tool to identify and rank yield defining, yield limiting and yield reducing factors for those agro-ecological zones where the potato is currently grown. With these procedures, the physiological age of seed tubers and virus diseases were identified as the most relevant factors limiting and reducing yield. Specific strategies can be developed to counteract their limiting and reducing effects upon seed quality and tuber yield. The approach of this work does not only apply for the specific situation of the potato crop in Argentina, but this framework could be successfully applied to other crops or production systems elsewhere