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The aim of this study was to use the Eurotate_N crop simulation model in order to reduce application rates of nitrogen to commercial potato fields located in the Oja’s NVZ.
2. Materials & Methods Two experiments were carried out throughout 2010 in farm fields, sited in the NVZ. Each experiment had three treatments with different nitrogen fertilization management: Traditional Farming Practice (TFP), fertilization following the codes of Good Agricultural Practices (GAP) and optimal fertilization using the Eurotate_N model (EU). Experimental design was completely randomized with four replicates per treatment. In the EU Treatment optimal fertilization was defined before fertilizer was applied by carrying out a series of simulations with increasing doses of N and entering the updated data from the crop onto the model. In each simulation we determined the minimal dose of N applied that, without causing significant deficit of N in the crop, showed a suitable commercial production for our crop conditions. To assess the N deficit, N in plant and critical N simulated by the model were obtained and the nitrogen nutrition index (NNI) based on the critical N (minimum N concentration required for maximum growth) was used (NNI = N%actual/N%critical) (Gastal and Lemaire, 2002). Soil moisture content, soil mineral nitrogen, dry matter and nitrogen in the crop were measured throughout the crop season on a monthly basis in order to test and perform the simulations with the model. Weather data required by the model was obtained from a weather station located near the two farm fields. For each treatment in both experiments, residual nitrogen in soil, crop total-N uptake, accumulated dry matter and marketable yield were compared by analysis of variance with Systat® 12.0 (Systat software). The values of simulation carried out with the N dose selected as optimal (N dose applied in the EU treatment) were compared with the observed data in the EU treatment by the Student’s t test.
3. Results & Discussion Nitrogen applied to the EU treatment was 74 and 89 kg ha-1 lower than TFP treatment in experiments 1 and 2, respectively (Table 1). At the time of harvest there were no significant differences between treatments in marketable yield, total biomass production and total N extracted by the plant. The residual N in the soil up to 60 cm depth was low in the two experiments for all treatments, 38 2.4 and 35 2.9 kg N ha-1 on average in experiments 1 and 2, respectively (Table 1). In addition, Table 1 shows the most relevant values of the simulation carried out on both experiments with optimal dose (EU treatment) on the Eurotate_N model. No significant differences were found, between the simulated values and those measured in the field, for marketable yield, biomass production and N extraction in any of the experiments. In contrast, the measured values of soil mineral N up to 60 cm were higher than those simulated by the model up to 90 cm.
From the results, it can be suggested that the difference of N fertilizer applied for the TFP and GAP treatments compared to the EU could be lost by leaching, mainly through irrigation water, as observed in previous studies in the area (Olasolo, 2007). These results suggest that the pre-sowing fertilization applied by the farmer could be reduced by 70% with consequent savings in fertilizer and decreased risk of N leaching. Similarly, the side-dress fertilization can be reduced by an adequate partition of nitrogen fertilizer application as in the EU treatment (Table 1). The model simulations were successful and allowed a reduction in the N applied to the crop, however further studies should be carried out in order to reduce the differences between observed and simulated data of soil mineral N.
4. Conclusions Using the model a reduction of up to 43% of the applied N on the crop was possible. Furthermore, this reduction can be made without a decline in production compared to that obtained by the farmer.
The usefulness of the Eurotate_N model in giving potato crop fertilization recommendations in the farm fields studied has been proven.
References EU-RotateN, 2002. Project number QLK5-2002-01110. http://www2.warwick.ac.uk/fac/sci/whri/research/nitrogenand environment/eurotaten/ Gastal, F. and Lemaire G. 2002. N uptake and distribution in crops: an agronomical and ecophysiological perspective.
Journal of Experimental Botany 53 (370), 789-799.
Olasolo, L., Vázquez, N., Suso, ML. and Pardo, A. 2007. Estimación del drenaje y lavado de nitratos en un cultivo de patata en la zona vulnerable del aluvial del oja. Actas de horticultura 49, 249-252.
Olasolo, L., Vázquez, N., Suso, ML. and Pardo, A. 2009. Preliminary evaluation of the crop model Eu-Rotate_N in a pea-green bean rotation. In Proceedings of the 16th Nitrogen workshop. Connecting different scales of nitrogen use in agriculture: 547-548.
Olasolo, L., Vázquez, N., Suso, ML. and Pardo, A. 2011. Evaluación del modelo EU-Rotate_N en cultivo de patata.
Actas de Horticultura (in press).
The Challenge of Feeding 9-10 billion People Equitably and Sustainably Godfray, H.C.J.
Oxford Martin Programme on the Future of Food, University of Oxford, Dept. Zoology, South Parks Rd., Oxford OX1 3PS
1. Introduction Over the last forty years the price of food, at least as experienced by people living in high-income countries, has been in real-terms at historically low levels (Dorward, 2011). The major policy issue concerning food supply in developed countries has been how to support farmers who in a high-wage economy could not survive if exposed to the price of food on world markets. Investment in agricultural research has declined in the face of over-production, and the rate of increase in yields has slowed (Piesse and Thirtle, 2010). The widespread mid-century pessimism about the world’s ability to feed itself was allayed by the great advances in productivity of the Green Revolution (Evenson and Gollin, 2003), and though large numbers of people still suffer from hunger, progress in reducing this number has until recently been good and it had looked as if the Millennium Development Goals on hunger were going to be met by 2015 (United Nations, 2009). Though many voices had raised concerns about the long-term viability of current modes of food production, sustainability has not been a central concern of food producers. Issues of balancing the demand and supply of food, and of keeping food prices within boundaries accepted by society, has not been the dominant political issue that it has been for most of human history.
The last five years has seen a sea-change in the attention paid to the security of food supply. The proximate reason for this was the sudden jump in food prices in 2007/2008 and their persistence and high volatility since then (Figure 1).
The origins of the food price spikes are still strongly debated and are likely to be a mixture of long-term trends interacting with more short-term factors (Swinnen and Squicciarini, 2012, Piesse and Thirtle, 2009, HMG, 2010). Of the former, the secular increase in food demand from a growing, richer population, especially in Southeast Asia, is particularly important. There has also been a long-term trend to reduce food stocks (in both the private and public sector) so that stock-to-use ratios were at historically low levels. By the end of the first decade of the current century the growth Nitrogen Workshop 2012 in land area that had switched from food to biofuel production grew large enough to begin to impact on supply. Of the more short-term factors the flight of investment capital into commodities during the financial crisis, as well as poor harvests in Australia and elsewhere, were also likely to have had some effect.
2. What might happen to the food system in the next forty years Further analysis is required to understand the factors influencing current supply but the major food price spikes led to the commissioning of a series of reports that explored what might happen to food supplies over a longer period of time, typically to mid-century (IAASTD, 2008; Foresight, 2011; Paillard et al., 2009; World Bank, 2008). Though their conclusions differ in detail, there is general agreement that the global food system is entering into a new phase where excess demand will replace excess supply as the dominant policy issue in the rich world, with great risks that recent progress in reducing hunger in the poor world will stall or reverse. Unless action is taken throughout the food system there is a real likelihood of food price rises that will give rise to political and economic dislocation. The reports also look at food production within an environmental context, not only the challenges of climate change but more generally the negative effects that current food production has on many aspects of the environment. Again there is general agreement that the way we produce food now undermines our ability to produce food in the future: we are eating into the natural capital upon which future food production will need to rely. For example, intensive agriculture that negatively effects soil structure reduces the capability of the land to produce food in the future.
The challenges to the food system are both on the demand and supply side (Godfray et al., 2010). As mentioned above demand will increase because there will be more mouths to feed as populations grow. Current estimates suggest that global populations will plateau somewhere between 9 and 10 billion in the second half of this century, but there is considerable uncertainty and recent estimates have tended to be revised upwards (Lutz and Samir, 2010). Average wealth will have increased which in many ways is a good thing (especially as richer societies tend to have lower fertility) but wealthier people demand a more varied diet and typically consume food types that require more resources to produce, for example many types of meat. The dramatic increase in meat consumption in China over the last few decades is already reshaping trade in agricultural commodities (Anderson, 2010). This rising demand will need to be met at the same time as a nexus of different factors threaten supply. Perhaps the most critical in the short term is water. Competition for freshwater will become ever fiercer from a growing population while more will need to be retained to allow the environmental flows that we now understand are essential to keep ecosystems functioning (Strzepek and Boehlert, 2010). Many highly productive irrigated areas currently rely on water pumped from underground aquifers that are being exploited at rates far in excess of the rates at which they are replenished. We shall see currently fertile areas of irrigated agriculture abandoned in the next few decades. To produce our food most types of agriculture require energy, both directly to power machinery, refrigeration etc., but indirectly in manufacturing agricultural inputs, in particular nitrogen fertiliser. No one can confidently predict energy prices into the future, but we shall most likely see an increase in energy costs, and probably much greater volatility (International Energy Agency, 2012). And overarching these supply side issues is the existential challenge of climate change (IPCC, 2007). It is currently very hard to predict exactly how climate change will impact future food production. Some regions will actually benefit from climate change and it is likely that the northern boundary of many crops will advance towards the pole. However, it is almost certain that the Nitrogen Workshop 2012 negative consequences will outweigh (probably strongly outweigh), the positive. We shall see changes in temperature and rainfall patterns, and adapting to these conditions will be a major challenge for farmers. The frequency of extreme events will increase, and we shall see more storms, floods and droughts, and these are likely to affect larger spatial areas. In some places, most likely the arid tropics, agriculture or pastoralism may no longer be possible (Gornall et al., 2010).
What might these supply and demand pressures mean to prices? Given that food is at the present time relatively cheap and people in the future will be wealthier, a modest increase in prices that consumers can afford might actually stimulate more investment and innovation in food production. Predicting future food prices is hugely difficult and a craft rather than a science. It is largely done using economic models that assume equilibrium conditions – that prices quickly adjust to supply and demand in a world where all actors act rationally. They are essentially the only tools we have, though their projections must be treated with great caution. One of the best models available is called “IMPACT” and is operated by the International Food Policy Research Institute in Washington (Rosegrant et al., 2008). Not only does it have a core economic module, but it has further components that integrate expected climate change scenarios as well as competition for water in the world’s river basins.
IMPACT can try to predict what happens to food prices in a world where current trends in the global food system continue and it is pretty much business as usual, or the same world but with climate change. The results are disturbing (Nelson et al., 2009, Nelson et al., 2010). In the absence of climate change the prices of most commodities rise by about 30-70% between 2000 and 2050. However, in the presence of climate change the price rises are much higher. For example, for staple grains price rises of well over 100% are projected.
Figure 2. Projected increases in the price of selected food items between 2000 and 2050 with and without climate change.
Source: Nelson et al. (2009).
It is important to reiterate that these projections should be treated with great caution, and that the precise numbers should not be given undue weight. But at the very least this and other studies that have come to similar conclusions, show that we need to pay more attention to food security. Food price rises of the magnitude described in Figure 2 would result in major political and economic disturbances. Even the relatively modest price increases of the last five years resulted in food riots in several African and south Asian states and in the fall of at least one government (Madagascar)
Nitrogen Workshop 2012
(Abbott and de Battisti, 2011). The ramifications of a doubling in food prices would be enormous.