This study investigates the economics of water as used by smallholder irrigation farmers in South Africa. The productivity and value of water were estimated with data from two smallholder irrigation schemes: Zanyokwe and Thabina. Production parameters such as fertilisers, seeds, pesticides, equipment, transport, labour, and water were treated as inputs. Various methodologies used to estimate water value, including cost-based approaches, were thoroughly reviewed. The aim was to select the ones with more justification for use in smallholder irrigation sector and also to compare a number of approaches. On a case study basis, three methods were applied: residual valuation method, willingness to pay and cost-based approaches (i.e. accounting costs of O&M). Water productivity and values were then evaluated as per crop, farmer, and scheme. Also, cross-section regression analysis was used to investigate the effect of some key socio-economic factors of production on gross margin and willingness to pay. The results indicated that on average, the value of water varies according to methods, crops, farmers and schemes. In the Zanyokwe scheme, water value estimated by the residual method in cabbage is higher (R1.64 per m3) than the one in dry maize (R0.35 per m3), if intensive and high yield irrigated crops are grown per year. Also, in Thabina, water value for cabbage (R1.14 per m3) outperforms water value for dry maize (R0.02 per m3. This means that there is greater potential in vegetable crops than food grain crops, although the two schemes have different irrigation systems, and such analysis is based on one-year data, which may lack accuracy. Low water valuation is ascribed to low yield and extensive cropping systems, because gross margin per hectare is very low. This signifies the need for expansion in high value crops rather than low value crops. At farm and scheme level, the results were derived by using the Smile database and simulated platform. The Smile platform is a data capturing and a calculation tool. It calculates a number of indicators, economic figures, at scheme and individual farm level, allowing for evaluation of the current situation. The results suggested that at present, the Zanyokwe scheme requires about 1 739 255 m3 of irrigation water per year. The total operational costs (accounting costs of O&M) are about R146 097.42. In other words, supplying 1 m3at farm level will cost R0.084. This implies that if irrigation charges are levied so as to cover O&M costs of the Zanyokwe scheme, the current costs (R0.084) will form only 23% of the average gross margin of R0.37 per m3 used at scheme level. Furthermore, in the Zanyokwe irrigation scheme, the results revealed that the most active and efficient farmers (specialized farmers) can make an average gross margin of R4 105 per ha per year, also achieving the highest water productivity R0.69 in gross margin per m3 consumed. However, in the Thabina scheme, the results indicated that, to supply 1 m3will cost R0.062. Thus, the current water supply costs cover about 56 % of what is earned (i.e. R0.11 per m3 used) at scheme level. Again, the most active farmers (commercially oriented pensioners) are more efficient, with average gross margin of R3 092 per ha per year, also achieving the highest water productivity (R0.53 in gross margin per m3 used). These results suggested that certain smallholder farming systems seem capable of paying for irrigation charges of their respective schemes if they are obliged to do so. As far as willingness to pay (WTP) and cost-based approaches (CBA) are concerned, the results clearly show that the active farmers in the Zanyokwe scheme have lower WTP per m3 (R0.03) than the GM of output (R0.69) per m3 of water used. Also, the accounting cost (R0.084 per m3 of water used) is lower than the GM gained. However, in the Thabina scheme, the situation is quite different. The active farmers are willing to pay R0.19 per m3 of water used. This implies that, if farmers are to pay for the charges in order to cover O&M costs, the farmers in Thabina are ready to pay as much as three times the proposed costs of O&M (R0.062 per m3 of water used), although both the WTP and the accounting cost are lower than GM gained. In these results, it is significant that both the accounting cost and the willingness to pay are lower than the GM per m3 of water used at least in the Zanyokwe scheme. Even though the data were drawn from a sample for one year only, this finding on the perception of farmers has implications for extension and training to improve future productive use. Regarding the findings from cross-section regression analysis, the results for GM (as dependent variable) in general indicated that in the Zanyokwe scheme, only credit affects output positively and significantly. Production costs have significant effect on output, but with a negative correlation. It is striking that all the other factors of production including hired labour show negative and insignificant effects on output. In the Thabina scheme, the most important factors of production in the model are land size (hectare) and production costs (Rand per ha). These two variables influence output positively and significantly. As far as WTP (as dependent variable) is concerned, the results indicated that in the Zanyokwe scheme, it is striking that in all the investigated factors, only credit affects WTP positively and significantly. All other factors are insignificant. Also, gross margin of output per m3, unexpectedly, has displayed a negative and insignificant effect on output. In the Thabina scheme, the results show that the land size per hectare, and gross margin of output per m3 affect WTP positively and significantly. Such results are consistent with the assumptions made in the conceptual framework that a farmer with high gross margin gained at farm level is more likely to pay for water costs than those with poor gross margin. On the basis of these findings, the following recommendations were formulated. Specific policies should include promotion of high value crops and improved varieties of seed for food grain crops (e.g. maize) and vegetables (e.g. cabbage). While improved agronomic practices remain important, there is also potential to increase productivity and profitability of the crops by improving water management practices at the canal-system level, such as better timing of water delivery and increased overall canal-water supplies at the farm level. Finally, from a cost recovery point of view, government should develop a program of cost sharing for capital costs of irrigation development. With regard to inter-sectoral competition, these results highlight that, if inter-sectoral competition is left to uncontrolled market forces may result in smallholder farmers' selling their water rights to sectors which value water at higher levels. To avoid a “liberal trap” such as in the example of Chile (where smallholder farmers "en masse" sold their water rights, resulting ultimately in deeper rural poverty), some form of control/management of water rights transaction involving smallholder farmers is necessary. Finally, the findings of this study can be used in various ways. Since, these values determine the farmer’s ability to pay for water now or in the future, the incentive to use water judiciously will be governed by these values. Secondly, the results can be used to evaluate whether the costs estimated and gross margin per m3 gained at farm level, are in line with the farmers’ willingness to pay. Further work is recommended to clarify these conclusions and provide more policy clarification on the better use of water by smallholder irrigation farmers in South Africa. / Dissertation (MInst.Agrar)--University of Pretoria, 2007. / Agricultural Economics, Extension and Rural Development / unrestricted

O objetivo neste experimento foi quantificar a evapotranspiração de diferentes variedades de cana-de-açúcar, a produtividade de biomassa e energia (fotossíntese acumulada), bem como a produtividade da água (PA), submetidas à irrigação plena e sob déficit, durante o estádio de enchimento e crescimento dos colmos, em três ciclos de cultivo sequenciais (2009, 2010 e 2011). Dois experimentos nomeados Experimento 1 e Experimento 2 foram instalados e desenvolvidos em casa de vegetação, com 23 variedades, em vasos com volume de 0,5 m3. No Experimento 1 foram avaliadas 9 variedades, sendo elas RB855453, RB855536, RB925211, RB867515, SP89-1115, SP81-3250, CTC14, CTC8 e CTC6 implantadas em um solo de textura argilosa, classificado como Nitossolo Vermelho Eutrófico. Outras 14 variedades (RB925345, RB855156, RB966928, RB72454, RB92579, IACSP95-5000, Caiana, SP83-2847, SP90-3414, SP79-1011, CTC17, CTC15, CTC9 e CTC2) foram implantadas no Experimento 2 em um solo de textura franco-arenosa, classificado como Latossolo Vermelho Amarelo. Em ambos os experimentos as variedades foram submetidas à irrigação plena e à irrigação sob déficit. O manejo da irrigação foi realizado através de irrigação por gotejamento mediante controle do potencial mátrico, via tensiômetros instalados em diferentes profundidades. Em todos os ciclos e para cada variedade e cada tipo de manejo da irrigação (com e sem déficit), foram avaliadas a biomassa fresca de colmo (BFC), os parâmetros tecnológicos, o rendimento bruto de açúcar (RBA), a fotossíntese acumulada (biomassa seca da parte aérea), a energia total da biomassa (ET) e a produtividade da água da BFC, do RBA e da ET. Os fatores que mais influenciaram na fotossíntese acumulada (biomassa e energia), e consequentemente na produtividade da água durante os três ciclos de cultivos nas variedades estudadas foram a radiação e a disponibilidade hídrica no solo. A produtividade da água em BFC (PABFC) no solo de textura argilosa atingiu valor máximo de 29,10 Kg.m-3 na variedade CTC6, sob irrigação plena e mínimo de 11,50 Kg.m-3 na variedade RB855536 em condições de déficit. A produtividade da água em biomassa de rendimento bruto de açúcar (PARBA) variou de 1,44 a 3,52 Kg.m-3. A produtividade da água em energia total (PAET), no solo de textura argilosa alcançou melhor resultado na variedade SP81-3250 com 176,32 MJ.m-3. No solo de textura franco-arenosa a PABFC variou de 8,13 a 26,39 K.m-3, na PARBA a variação foi de 0,99 a 3,42 Kg.m-3 e na PAET a variação foi de 64,89 a 192,92 MJ.m-3. / The objective of this experiment was to quantify evapotranspiration in different varieties of sugar cane, biomass productivity and energy (accumulated photosynthesis), biomass productivity and energy as well as the water productivity, subjected to full and deficit irrigation, for three sequential crop cycles (2009, 2010 and 2011). Two experiments named Experiment 1 and Experiment 2 were installed and developed under greenhouse conditions, , with 23 varieties planted in vases with volume of 0.5 m3. In the Experiment 1 were evaluated nine varieties: RB855453, RB855536, RB925211, RB867515, SP89-1115, SP81-3250, CTC14, CTC8, CTC6, and implanted in clay texture soil, classified as Nitossolo Vermelho Eutrófico. Other 14 varieties (RB925345, RB855156, RB966928, RB72454, RB92579, IACSP95- 5000, Caiana, SP83-2847, SP90-3414, SP79-1011, CTC17, CTC15, CTC9 and CTC2) were implanted in Experiment 2 in the sandy loam soil texture, classified as Latossolo Vermelho Amarelo. In both experiments the varieties were subjected to full irrigation and deficit irrigation. The water management was accomplished through trickle irrigation system by monitoring tensiometers installed at different depths. In all cycles and for each variety and each type of irrigation management (with and without deficit) were evaluated stems fresh biomass, technological parameters, sugar gross yield, the cumulative photosynthesis (shoot dry biomass), biomass total energy and water productivity of the stems fresh biomass, of the sugar gross yield and of the total energy. The factors that most influenced the cumulative photosynthesis (biomass and energy), and consequently the water productivity during crop three cycles in varieties studied were radiation and water supply. The water productivity in stems fresh biomass in clay texture soil reached a maximum of 29.10 kg.m-3 in the variety CTC6 under full irrigation, and minimum of 11.50 kg.m-3 in the variety RB855536 in deficit conditions. The water productivity in biomass of sugar gross yield ranged from 1.44 to 3.52 Kg.m-3. The water productivity in total energy, in clay soil achieved better result in the variety SP81-3250 with 176.32 MJ.m-3. In sandy loam soil the water productivity of stem fresh biomass varied from 8.13 to 26.39 Kg.m-3, in water productivity of sugar gross yield the variation was 0.99 to 3.42 Kg.m-3 and in the water productivity of total energy the variation was 64.89 to 192.92 MJ.m-3.

O Brasil é o maior exportador mundial de carne e possui o maior rebanho comercial de bovinos do mundo. As pastagens, por apresentarem baixo custo de produção em relação aos alimentos concentrados, constituem-se na base da alimentação do rebanho bovino brasileiro. Com isso, grande parte da carne e do leite produzidos no país provêm de rebanhos mantidos a pasto. Dentre as espécies forrageiras destacam-se as cultivares de Panicum maximum por apresentarem elevada produtividade, qualidade e valor nutritivo, embora sejam exigentes em água, radiação solar e nutrientes. São escassas as informações na literatura sobre o manejo da irrigação para as espécies forrageiras. Objetivou-se neste trabalho avaliar a influência do manejo da irrigação nas trocas gasosas, na altura, na produção de fitomassa fresca e seca da parte aérea, e na área foliar do capim-mombaça. Adotou-se o delineamento de blocos aleatorizados em um experimento com dois solos de texturas distintas: Latossolo Vermelho Amarelo distrófico (série \"Sertãozinho\") franco-arenoso e Nitossolo Vermelho (série \"Luiz de Queiroz\") franco-argiloso. Aplicaram-se quatro níveis de depleção da capacidade de água disponível do solo (15, 30, 45 e 60% da CAD) com quatro repetições. A pesquisa foi realizada em casa de vegetação na Escola Superior de Agricultura \"Luiz de Queiroz\" - ESALQ/USP, no município de Piracicaba-SP. A umidade dos solos foi controlada por meio de pesagens diárias dos vasos; foram realizados três cortes da parte aérea do capim. Determinaram-se a produtividade da água, as lâminas de irrigação aplicadas, os turnos de rega médios e a sensibilidade do capim-mombaça ao déficit hídrico. A taxa líquida de assimilação de CO2, a altura das plantas e a fitomassa fresca e seca foram afetadas pela condição hídrica do solo; a produtividade da água foi maior conforme o incremento do nível de água no Nitossolo; o capim foi sensível ao déficit hídrico, apresentando produção superior de massa seca quando cultivado sob o nível de 30% de depleção de água para ambos os solos. / Brazil is the world\'s largest meat exporter and has the largest commercial cattle herd in the world. Pastures, because they have low production costs in relation to food concentrates, constitute the staple diet of the Brazilian cattle herd. Thus, much of the meat and milk produced in the country comes from cattle kept at pasture. Among the forage species, there are the cultivars of Panicum maximum for presenting high productivity, quality and nutritional value, although they are demanding in water, light and nutrients. The information in the literature on irrigation management for forage species is scarce. The aim of this study was to evaluate the influence of irrigation management in gas exchange, in the yield of fresh and dry weight of canopy, and leaf area of mombaca grass; and to determine the productivity of water, irrigation depths applied, the average irrigation frequency and sensitivity of mombaca grass to water deficit. The research was carried at \"Escola Superior de Agricultura Luiz de Queiroz\" - ESALQ/USP in greenhouse at Piracicaba-SP city. The experiement was set up in randomized blocks consisted by four levels of depletion of soil water availability (15, 30, 45 and 60%) applied to two soils - a Sandy loam Distrofic Yellow Red Latosol and a Clay loam Red Nitosol with four replications. Soil moisture was controlled by the weight of the experimental plots and the grass was cropped three times. The photosynthesis rate, the height and the weight of fresh and dry canopy of the plants was affected by soil moisture; water productivity increases as soil moisture was increased in Nitosol. Mombaca grass has shown sensible to drought and about thirty per cent of soil water depletion proportioned the better yield response for both soils.

O crescimento da população mundial associado ao aumento da competição pelos recursos hídricos, desafiam a humanidade a buscar alternativas para solucionar os problemas de abastecimento de água e oferta de alimentos. Isso exige de pesquisadores e institutos de pesquisa soluções para aumentar a eficiência na produção de alimentos e na eficiência no uso dos recursos hídricos. O milheto (Pennisetum glaucum (L.) R. Br.) pode ser uma alternativa viável para a produção de biomassa e forragem com maior eficiência no uso da água. Deste modo, levanta-se a hipótese de que a diminuição na oferta de água aumenta a produtividade da água na cultura; o objetivo deste trabalho foi investigar o incremento de produtividade da água da cultura, associado à diminuição na oferta de água, bem como, o padrão de resposta termal da cultura em função do déficit hídrico. O estudo foi conduzido em um ambiente protegido na área de pesquisa do Departamento de Engenharia de Biossistemas da Escola Superior de Agricultura -Luiz de Queiroz? entre novembro de 2016 e janeiro de 2017. A variedade utilizada neste trabalho foi a BRS-1501, desenvolvida pela EMBRAPA, o delineamento experimental adotado foi o de blocos casualizados com quatro blocos e quatro níveis de reposição hídrica, sendo eles: (L40, L70, L100 e L130).O nível de reposição hídrica de referência (L100) foi mantido ao longo do experimento próximo à capacidade de campo (θcc). A unidade experimental considerada foi de uma caixa com uma área de 0,261 m2, com um volume de solo aproximado de 100 litros contendo seis plantas. Foram avaliados o potencial de água na folha, a temperatura foliar, para o cálculo do CWSI, e, na colheita, foi medido o índice de área foliar (IAF), e a produção de biomassa da parte aérea, para estimativa de produtividade de biomassa da parte aérea, e de água para a cultura. Os tratamentos foram aplicados aos 15 dias após a semeadura (DAS) e se seguiram até a colheita. As variáveis avaliadas apresentaram relações significativas com os tratamentos que foram impostos. O CWSI calculado para a cultura foi representativo e apresentou boa correlação com o potencial de água na folha no modelo linear. O índice de área foliar oscilou entre 5,9m2 m-2 e 9,4 m2 m-2, em valores médios, entre os tratamentos de irrigação. O valor máximo de produtividade de biomassa seca da parte aérea se deu no tratamento L130, com valor médio de 12,1 Mg ha-1, e o menor valor de produtividade de biomassa se deu no tratamento L40, com valor médio de 5,15 Mg ha-1. Os valores médios de produtividade de água foram expressivos para o tratamento de reposição L40, com valor aproximado de 9,1 kg m-3 de biomassa produzida, evidenciando a grande eficiência no uso da água pela cultura. / The growth of the world population associated with increased competition for water resources challenges humanity to seek alternatives to solve the problems of water supply and food supply. This requires researchers and research institutes to increase their efficiency in food production and the efficiency of their use of water resources. The millet (Pennisetum glaucum (L.) R. Br.) can be a viable alternative for the production of biomass and forage with greater efficiency in the use of water. Thus, it is hypothesized that the decrease in water supply increases the productivity of water in the crop; the objective of this work was to investigate the increase of crop water productivity, associated with the decrease in water supply, as well as the thermal response pattern of the crop as a function of the water deficit. The study was conducted in a protected environment in the research area of the Department of Biosystems Engineering of the \"Luiz de Queiroz\" School of Agriculture between November 2016 and January 2017. The variety used in this work was BRS-1501, developed by EMBRAPA, the experimental design was a randomized block design with four blocks and four water replenishment levels: (L40, L70, L100 and L130). The reference water replenishment level (L100) was maintained throughout the experiment close to the field capacity (θcc).The experimental unit considered was a box with 0.261 m2 containing six plants. Leaf water potential, leaf temperature, for the CWSI calculation, leaf area index (LAI) and leaf biomass production were estimated for estimating biomass productivity of aerial part, and of water for the culture. The treatments were applied at 15 days after seeding (DAS) and were followed until harvest. The evaluated variables presented significant relationships with the treatments that were imposed. The CWSI calculated for the crop was representative and showed good correlation with the leaf water potential in the linear model. The leaf area index ranged from 5.9 m2 m-2 to 9.4 m2 m-2, in average values, between irrigation treatments. The maximum productivity of dry biomass of aerial part was given in the treatment L130, with average value of 12.1 Mg ha-1, and the lowest value of biomass productivity occurred in the treatment L40, with an average value of 5,15 Mg ha-1. The mean values of water productivity were significant for the L40 replacement treatment, with an approximate value of 9.1 kg m-3 of biomass produced, evidencing the great efficiency in the use of crop water.

Irrigated agriculture is the primary consumer of limited worldwide freshwater resources. Drought, growing world populations, and environmental demands compete with irrigation for freshwater resources"”threatening sustainable global food, fuel, and fiber production. This escalating global crisis demands that agriculture produce more food using less water. Traditional irrigation management has used technology to apply uniform irrigation rates across landscapes"”ignoring natural environmental variation. This provides inherent inefficiencies of over- or under- irrigation within individual fields. Variable-rate irrigation (VRI) is modern technology that employs global positioning systems and geographic information systems to match irrigation to spatially variable crop water demands within a field. Although commercially available, VRI lacks scientifically validated decision support systems to determine spatially and temporally variable crop water demand. The purpose of this research is to explore spatial and temporal variations in crop water demand to inform growers utilizing VRI. This research consists of four seasons of winter wheat (Triticum aestivum L.) production on a commercial farm in Idaho that employs a VRI system. In Chapter 1, the spatial variation of crop water productivity (CWP, the grain produced per unit of water consumed), is characterized for two seasons (2016-2017) and we propose a unique conceptual strategy for VRI management targeted at CWP. Observed CWP ranged from 4.1-21 kg ha-1 mm-1 with distinct spatial variation that, when considered together with grain yield, were shown to be useful for VRI management. During the 2017 growing season, VRI zones conserved 25% of irrigation compared to traditional uniform irrigation management. In the second chapter the spatial variation of soil water holding capacity (SWHC) was measured at 90 sampling points throughout the field. Then, during the 2016-2017 growing seasons, the spatial and temporal variation of soil moisture were modelled to characterize crop stress and its influence on grain yield. Soil within the field showed large spatial variation of SWHC, ranging from 147-369 mm. Under uniform irrigation in 2016, the natural variation of TAW created 21 day variation in the onset of crop stress throughout the field and under VRI in 2017 the onset of crop stress spanned 56 d. Surprisingly the variations in TAW did not statistically influence yield in 2016, and in 2017 the rate of irrigation predicted yield and TAW again did not statistically predict yield. This suggests that other environmental variables should be included when delineating irrigation zones and rates for VRI.

O Brasil é o maior exportador mundial de carne e possui o maior rebanho comercial de bovinos do mundo. As pastagens, por apresentarem baixo custo de produção em relação aos alimentos concentrados, constituem-se na base da alimentação do rebanho bovino brasileiro. Com isso, grande parte da carne e do leite produzidos no país provêm de rebanhos mantidos a pasto. Dentre as espécies forrageiras destacam-se as cultivares de Panicum maximum por apresentarem elevada produtividade, qualidade e valor nutritivo, embora sejam exigentes em água, radiação solar e nutrientes. São escassas as informações na literatura sobre o manejo da irrigação para as espécies forrageiras. Objetivou-se neste trabalho avaliar a influência do manejo da irrigação nas trocas gasosas, na altura, na produção de fitomassa fresca e seca da parte aérea, e na área foliar do capim-mombaça. Adotou-se o delineamento de blocos aleatorizados em um experimento com dois solos de texturas distintas: Latossolo Vermelho Amarelo distrófico (série \"Sertãozinho\") franco-arenoso e Nitossolo Vermelho (série \"Luiz de Queiroz\") franco-argiloso. Aplicaram-se quatro níveis de depleção da capacidade de água disponível do solo (15, 30, 45 e 60% da CAD) com quatro repetições. A pesquisa foi realizada em casa de vegetação na Escola Superior de Agricultura \"Luiz de Queiroz\" - ESALQ/USP, no município de Piracicaba-SP. A umidade dos solos foi controlada por meio de pesagens diárias dos vasos; foram realizados três cortes da parte aérea do capim. Determinaram-se a produtividade da água, as lâminas de irrigação aplicadas, os turnos de rega médios e a sensibilidade do capim-mombaça ao déficit hídrico. A taxa líquida de assimilação de CO2, a altura das plantas e a fitomassa fresca e seca foram afetadas pela condição hídrica do solo; a produtividade da água foi maior conforme o incremento do nível de água no Nitossolo; o capim foi sensível ao déficit hídrico, apresentando produção superior de massa seca quando cultivado sob o nível de 30% de depleção de água para ambos os solos. / Brazil is the world\'s largest meat exporter and has the largest commercial cattle herd in the world. Pastures, because they have low production costs in relation to food concentrates, constitute the staple diet of the Brazilian cattle herd. Thus, much of the meat and milk produced in the country comes from cattle kept at pasture. Among the forage species, there are the cultivars of Panicum maximum for presenting high productivity, quality and nutritional value, although they are demanding in water, light and nutrients. The information in the literature on irrigation management for forage species is scarce. The aim of this study was to evaluate the influence of irrigation management in gas exchange, in the yield of fresh and dry weight of canopy, and leaf area of mombaca grass; and to determine the productivity of water, irrigation depths applied, the average irrigation frequency and sensitivity of mombaca grass to water deficit. The research was carried at \"Escola Superior de Agricultura Luiz de Queiroz\" - ESALQ/USP in greenhouse at Piracicaba-SP city. The experiement was set up in randomized blocks consisted by four levels of depletion of soil water availability (15, 30, 45 and 60%) applied to two soils - a Sandy loam Distrofic Yellow Red Latosol and a Clay loam Red Nitosol with four replications. Soil moisture was controlled by the weight of the experimental plots and the grass was cropped three times. The photosynthesis rate, the height and the weight of fresh and dry canopy of the plants was affected by soil moisture; water productivity increases as soil moisture was increased in Nitosol. Mombaca grass has shown sensible to drought and about thirty per cent of soil water depletion proportioned the better yield response for both soils.

O objetivo neste experimento foi quantificar a evapotranspiração de diferentes variedades de cana-de-açúcar, a produtividade de biomassa e energia (fotossíntese acumulada), bem como a produtividade da água (PA), submetidas à irrigação plena e sob déficit, durante o estádio de enchimento e crescimento dos colmos, em três ciclos de cultivo sequenciais (2009, 2010 e 2011). Dois experimentos nomeados Experimento 1 e Experimento 2 foram instalados e desenvolvidos em casa de vegetação, com 23 variedades, em vasos com volume de 0,5 m3. No Experimento 1 foram avaliadas 9 variedades, sendo elas RB855453, RB855536, RB925211, RB867515, SP89-1115, SP81-3250, CTC14, CTC8 e CTC6 implantadas em um solo de textura argilosa, classificado como Nitossolo Vermelho Eutrófico. Outras 14 variedades (RB925345, RB855156, RB966928, RB72454, RB92579, IACSP95-5000, Caiana, SP83-2847, SP90-3414, SP79-1011, CTC17, CTC15, CTC9 e CTC2) foram implantadas no Experimento 2 em um solo de textura franco-arenosa, classificado como Latossolo Vermelho Amarelo. Em ambos os experimentos as variedades foram submetidas à irrigação plena e à irrigação sob déficit. O manejo da irrigação foi realizado através de irrigação por gotejamento mediante controle do potencial mátrico, via tensiômetros instalados em diferentes profundidades. Em todos os ciclos e para cada variedade e cada tipo de manejo da irrigação (com e sem déficit), foram avaliadas a biomassa fresca de colmo (BFC), os parâmetros tecnológicos, o rendimento bruto de açúcar (RBA), a fotossíntese acumulada (biomassa seca da parte aérea), a energia total da biomassa (ET) e a produtividade da água da BFC, do RBA e da ET. Os fatores que mais influenciaram na fotossíntese acumulada (biomassa e energia), e consequentemente na produtividade da água durante os três ciclos de cultivos nas variedades estudadas foram a radiação e a disponibilidade hídrica no solo. A produtividade da água em BFC (PABFC) no solo de textura argilosa atingiu valor máximo de 29,10 Kg.m-3 na variedade CTC6, sob irrigação plena e mínimo de 11,50 Kg.m-3 na variedade RB855536 em condições de déficit. A produtividade da água em biomassa de rendimento bruto de açúcar (PARBA) variou de 1,44 a 3,52 Kg.m-3. A produtividade da água em energia total (PAET), no solo de textura argilosa alcançou melhor resultado na variedade SP81-3250 com 176,32 MJ.m-3. No solo de textura franco-arenosa a PABFC variou de 8,13 a 26,39 K.m-3, na PARBA a variação foi de 0,99 a 3,42 Kg.m-3 e na PAET a variação foi de 64,89 a 192,92 MJ.m-3. / The objective of this experiment was to quantify evapotranspiration in different varieties of sugar cane, biomass productivity and energy (accumulated photosynthesis), biomass productivity and energy as well as the water productivity, subjected to full and deficit irrigation, for three sequential crop cycles (2009, 2010 and 2011). Two experiments named Experiment 1 and Experiment 2 were installed and developed under greenhouse conditions, , with 23 varieties planted in vases with volume of 0.5 m3. In the Experiment 1 were evaluated nine varieties: RB855453, RB855536, RB925211, RB867515, SP89-1115, SP81-3250, CTC14, CTC8, CTC6, and implanted in clay texture soil, classified as Nitossolo Vermelho Eutrófico. Other 14 varieties (RB925345, RB855156, RB966928, RB72454, RB92579, IACSP95- 5000, Caiana, SP83-2847, SP90-3414, SP79-1011, CTC17, CTC15, CTC9 and CTC2) were implanted in Experiment 2 in the sandy loam soil texture, classified as Latossolo Vermelho Amarelo. In both experiments the varieties were subjected to full irrigation and deficit irrigation. The water management was accomplished through trickle irrigation system by monitoring tensiometers installed at different depths. In all cycles and for each variety and each type of irrigation management (with and without deficit) were evaluated stems fresh biomass, technological parameters, sugar gross yield, the cumulative photosynthesis (shoot dry biomass), biomass total energy and water productivity of the stems fresh biomass, of the sugar gross yield and of the total energy. The factors that most influenced the cumulative photosynthesis (biomass and energy), and consequently the water productivity during crop three cycles in varieties studied were radiation and water supply. The water productivity in stems fresh biomass in clay texture soil reached a maximum of 29.10 kg.m-3 in the variety CTC6 under full irrigation, and minimum of 11.50 kg.m-3 in the variety RB855536 in deficit conditions. The water productivity in biomass of sugar gross yield ranged from 1.44 to 3.52 Kg.m-3. The water productivity in total energy, in clay soil achieved better result in the variety SP81-3250 with 176.32 MJ.m-3. In sandy loam soil the water productivity of stem fresh biomass varied from 8.13 to 26.39 Kg.m-3, in water productivity of sugar gross yield the variation was 0.99 to 3.42 Kg.m-3 and in the water productivity of total energy the variation was 64.89 to 192.92 MJ.m-3.

O crescimento da população mundial associado ao aumento da competição pelos recursos hídricos, desafiam a humanidade a buscar alternativas para solucionar os problemas de abastecimento de água e oferta de alimentos. Isso exige de pesquisadores e institutos de pesquisa soluções para aumentar a eficiência na produção de alimentos e na eficiência no uso dos recursos hídricos. O milheto (Pennisetum glaucum (L.) R. Br.) pode ser uma alternativa viável para a produção de biomassa e forragem com maior eficiência no uso da água. Deste modo, levanta-se a hipótese de que a diminuição na oferta de água aumenta a produtividade da água na cultura; o objetivo deste trabalho foi investigar o incremento de produtividade da água da cultura, associado à diminuição na oferta de água, bem como, o padrão de resposta termal da cultura em função do déficit hídrico. O estudo foi conduzido em um ambiente protegido na área de pesquisa do Departamento de Engenharia de Biossistemas da Escola Superior de Agricultura -Luiz de Queiroz? entre novembro de 2016 e janeiro de 2017. A variedade utilizada neste trabalho foi a BRS-1501, desenvolvida pela EMBRAPA, o delineamento experimental adotado foi o de blocos casualizados com quatro blocos e quatro níveis de reposição hídrica, sendo eles: (L40, L70, L100 e L130).O nível de reposição hídrica de referência (L100) foi mantido ao longo do experimento próximo à capacidade de campo (θcc). A unidade experimental considerada foi de uma caixa com uma área de 0,261 m2, com um volume de solo aproximado de 100 litros contendo seis plantas. Foram avaliados o potencial de água na folha, a temperatura foliar, para o cálculo do CWSI, e, na colheita, foi medido o índice de área foliar (IAF), e a produção de biomassa da parte aérea, para estimativa de produtividade de biomassa da parte aérea, e de água para a cultura. Os tratamentos foram aplicados aos 15 dias após a semeadura (DAS) e se seguiram até a colheita. As variáveis avaliadas apresentaram relações significativas com os tratamentos que foram impostos. O CWSI calculado para a cultura foi representativo e apresentou boa correlação com o potencial de água na folha no modelo linear. O índice de área foliar oscilou entre 5,9m2 m-2 e 9,4 m2 m-2, em valores médios, entre os tratamentos de irrigação. O valor máximo de produtividade de biomassa seca da parte aérea se deu no tratamento L130, com valor médio de 12,1 Mg ha-1, e o menor valor de produtividade de biomassa se deu no tratamento L40, com valor médio de 5,15 Mg ha-1. Os valores médios de produtividade de água foram expressivos para o tratamento de reposição L40, com valor aproximado de 9,1 kg m-3 de biomassa produzida, evidenciando a grande eficiência no uso da água pela cultura. / The growth of the world population associated with increased competition for water resources challenges humanity to seek alternatives to solve the problems of water supply and food supply. This requires researchers and research institutes to increase their efficiency in food production and the efficiency of their use of water resources. The millet (Pennisetum glaucum (L.) R. Br.) can be a viable alternative for the production of biomass and forage with greater efficiency in the use of water. Thus, it is hypothesized that the decrease in water supply increases the productivity of water in the crop; the objective of this work was to investigate the increase of crop water productivity, associated with the decrease in water supply, as well as the thermal response pattern of the crop as a function of the water deficit. The study was conducted in a protected environment in the research area of the Department of Biosystems Engineering of the \"Luiz de Queiroz\" School of Agriculture between November 2016 and January 2017. The variety used in this work was BRS-1501, developed by EMBRAPA, the experimental design was a randomized block design with four blocks and four water replenishment levels: (L40, L70, L100 and L130). The reference water replenishment level (L100) was maintained throughout the experiment close to the field capacity (θcc).The experimental unit considered was a box with 0.261 m2 containing six plants. Leaf water potential, leaf temperature, for the CWSI calculation, leaf area index (LAI) and leaf biomass production were estimated for estimating biomass productivity of aerial part, and of water for the culture. The treatments were applied at 15 days after seeding (DAS) and were followed until harvest. The evaluated variables presented significant relationships with the treatments that were imposed. The CWSI calculated for the crop was representative and showed good correlation with the leaf water potential in the linear model. The leaf area index ranged from 5.9 m2 m-2 to 9.4 m2 m-2, in average values, between irrigation treatments. The maximum productivity of dry biomass of aerial part was given in the treatment L130, with average value of 12.1 Mg ha-1, and the lowest value of biomass productivity occurred in the treatment L40, with an average value of 5,15 Mg ha-1. The mean values of water productivity were significant for the L40 replacement treatment, with an approximate value of 9.1 kg m-3 of biomass produced, evidencing the great efficiency in the use of crop water.

This dissertation shows a novel strategy using soil matric potential based irrigation to improve water productivity of rice cultivation which is a case study from Sri Lanka. Study contains research component and a crop modelling component.:Introduction Fundamentals and Scientific Background Literature Review New Methods for Improving Water Productivity in Rice Cultivation Results and Discussion Conclusions and Outlook

A cana-de-açúcar apresenta-se como umas das principais culturas do agronegócio no Brasil e está integrada à matriz energética nacional, servindo também como matéria prima para diversos produtos industrializados. Em virtude das alterações nos padrões de precipitação natural que está ocorrendo em várias regiões do mundo, observam-se perdas significativas de produtividade na cana-de-açúcar devido ao déficit hídrico no solo, sendo esse um dos principais entraves atuais para maximização e para produtividade desta cultura. A busca por variedades resistentes ao estresse hídrico nos programas de melhoramento genético tem procurado selecionar genótipos que convertam de maneira mais eficiente à transpiração da planta em biomassa, evitando a perda de água excessiva para a atmosfera, de modo tal que a planta \"economize a água do solo\" para poder sobreviver posteriormente durante os períodos de estiagem. Este trabalho tem por hipótese que seja possível estimar a eficiência do uso da água (produtividade da água) e o acúmulo final de carbono na cultura de cana-de-açúcar em diferentes níveis de disponibilidade hídrica no solo, através de medidas pontuais da taxa de fotossíntese e transpiração (IRGA - Trocas gasosas) nos estágios iniciais e intermediários de crescimento da cultura. O presente trabalho tem por objetivo avaliar, de forma comparativa, variáveis relacionadas às trocas gasosas de oito variedades de cana-de-açúcar quando submetidas a déficit hídrico durante a fase inicial de crescimento vegetativo. O experimento foi conduzido em ambiente protegido na Escola Superior de Agricultura \"Luiz de Queiroz\" (USP), em Piracicaba-SP. Os tratamentos foram distribuídos em esquema fatorial (4x4x8) com parcelas sub-subdivididas com 3 repetições, totalizando 128 tratamentos e 384 parcelas experimentais. As mensurações de trocas gasosas foram realizadas entre 45 e 195 dias após inicio do ciclo cana soca sob condições controladas de luz e CO2. As quatro lâminas de irrigação utilizadas foram L50, L75 L100 e L125. Na lâmina L100 a umidade do solo foi mantida próxima à capacidade de campo (θcc) ao longo de todo experimento, nas demais lâminas aplicou-se uma fração da L100. Verificou-se que o estresse hídrico afetou as trocas gasosas: fotossíntese líquida, transpiração, condutância estomática e eficiência do uso da água. Os valores de produtividade da água reais medidos no experimento oscilaram entre 5 a 9 kg de matéria seca m-3 de água evapotranspirada. Os maiores acúmulos de biomassa foram observados para as variedades V1, V2 e V4 na lâmina de irrigação de 100%, com mais de 80 t ha-1 de biomassa seca. A produtividade da água real de uma variedade de cana-de-açúcar pode ser estimada com base em medidas de trocas gasosas, porém deverá ser aplicado um fator de correção específico para cada variedade que oscila entre 3,1 e 5,2 para a lâmina de 100 %. / Sugarcane crop is one of the main crops of agribusiness in Brazil and is integrated into the national energy matrix, also serving as raw material for various industrial products. Due to changes in natural precipitation patterns taking place in various regions of the world in recent years, there are significant losses of productivity in sugarcane due to water deficit in the soil, making a major current obstacle to maximizing this crop productivity. The search for varieties resistant to water stress in breeding programs has sought to select genotypes that convert more efficiently the transpiration of the plant, avoiding excessive loss of water to the atmosphere, such that the plant \"save water in the soil\" in order to survive during periods of drought in the future. This work has the primary hypothesis that it is possible to estimate the water use efficiency (water productivity) and the final accumulation of carbon in the sugarcane crop at different soil water levels availability through localized measurements of photosynthesis and transpiration (IRGA - Gas exchange equipment) during initial and intermediate stages of crop growth. This study aims to evaluate, on a comparative basis, variables related to gas exchange for 8 varieties of sugarcane subjected to water stress during early vegetative growth. The experiment was carried out under greenhouse conditions at Escola Superior de Agricultura \"Luiz de Queiroz\" (USP) in Piracicaba-SP / Brazil. The treatments were distributed in a factorial scheme (4x4x8) with sub-divided plots with three repetitions, totaling 128 treatments and experimental units. Measurements of gas exchange took place between 45 and 195 days after the beginning of the sugarcane cycle ratoon under controlled conditions of light and CO2. The four irrigation depths used were L50, L75 L100 and L125. In the L100 treatment soil moisture was kept close to field capacity (θcc) throughout the experiment; L50, L75 and L125 received a fraction of the L100. It was found that water stress affected plant gas exchange: net photosynthesis, transpiration, stomatal conductance and water use efficiency. The actual water use efficiency (water productivity) measured in the experiment varied between 5 and 9 kg of dry matter m-3 of evapotranspired water. The highest accumulation of biomass were observed for varieties V1, V2 and V4 on the L100 irrigation treatment, up to 83 t ha-1 dry matter (V1). Water use efficiency (water productivity) of sugarcane varieties can be estimated based on measurements of gas exchange, but must be assigned a specific correction variety factor ranging between 3.1 and 5.2 for the L100 tratment.