Sustainable Intensification of Global Agronomic Output

Agribusinesses are investigating sustainable ways to meet the predicted increased demand for food production due to an increasing world population and higher living standards. Therefore, there is a strong need to increase agronomic output. This paper will review the current state of agricultural production of the main annual top-five staple grain crops grown around the world, their current yields and harvested area averages and trends. It concludes with a discussion of which changes are needed to increase the yield in lower yielding areas of the world. Finally, there is an assessment of what level of yield increases that could be attained provided the proposed changes are made and its predicted impact on food security by 2050. The current yield trends and trends for harvested area, when extrapolated out to 2050, indicate crop production will increase 106%. This includes an expansion of the total crop production area by 31%. This increase of cropping area can be achieved by increased utilization of available, uncropped land suitable for crop production, increased double cropping, and relay intercropping, allowing for multiple crops in a calendar year. In order to double crop production by 2050, it is necessary to focus on growing crops where the conditions make it possible, adopt the best sustainable crop production practices and implement them as intensively as possible everywhere, and consider improved crop production machine system options to reduce risk of soil compaction, which can reduce crop yields. With proposed changes across the world, it will be possible to exceed a doubling of food production by 2050 relative to 2005 levels, providing a reasonable high level of food security, absent wars and widespread natural disasters.


Introduction
The population of the earth is expected to exceed 9 billion by the year 2050 (King et al., 2017;Taheri, Azadi, & D'Haese 2017), which puts pressure on agriculture around the world: More people will need to be fed from the land suitable for crop production, which will be in competition with more land needed for urban sprawl.Food demand is predicted to increase more rapidly than population growth due to change in dietary preferences.This effect has precipitated estimates for a need to increase the food production by 70-100% by 2050 (Borlaug, 2007;King et al., 2017).This dietary preference change is driven by a predicted growing level of prosperity.With increased prosperity comes a desire among people to include more animal protein in their diet (Dong & Fuller, 2010).As the demand for animal protein increases, so does the need for animal feedstock, which has to come from an increase in crop production.
In order to address this issue of ever-increasing food demand from the available land area suitable for crop production, emphasis needs to be placed on increased food production per unit of land per year.Smith (2013) offers a definition for this intensification of production done in a sustainable way, or "sustainable intensification", which reads "The process of delivering more, safe, nutritious food per unit of input resource, whilst allowing the current generation to meet its needs without compromising the ability of future generations to meet their own needs."Farmers in the future need to focus on creating the most suitable, sustainable conditions for plant growth and select the most appropriate crops in order to maximize the yield and nutritional content (Green et al., 2015).Some improvements can be expected from genetics development (Jaggard, 2010).Management systems focused on increasing land productivity will increase actual yields (Hatfield & Walthall, 2015), especially management of  In the cas America a able to sho America a increase is kg/ha/year Figure 4 The Europ Figure 5. Fi As seen in the bottom right hand field in Table 2, the trend line prediction for area harvested to the top-five grain crops will increase by 31.5% by 2050 relative to 2005.

Analysi
According to Bruinsma (2003), approximately 36% of the land suitable for crop production worldwide is used in crop production (1.5 of 4.17 billion hectares) in which appears to be 1999 data.Based on the analyzed data from FAOSTAT ( 2015), the increase in the predicted harvested area between 1999 and 2050, based on the linear curve fit equation, is 39%, which would be an increase of 241 million ha for the top-five grain crops.Assuming the needed increase for other crops is the same, then that will require an increase in the cultivated area worldwide from the 1.5 billion ha in 1999 to 2.1 billion ha in 2050, which will be 48% of the worldwide available area suitable for crop production, an additional 600 million ha or a 12%-age point increase.
Where will this additional harvested area come from?According to Bruinsma (2003) there are 1.8 billion ha of land suitable for rain fed crop cultivation with yield potential over an acceptable minimum level.Of this land, 90% of it is in sub-Saharan Africa and Latin America.The estimated amount of additional land available for cultivation in sub-Saharan Africa is more than 700 million ha.However, some of these lands may not be profitable to farm due to lack of available efficient markets for inputs and outputs and due to poor or lacking infrastructure (FAO, 2009).
The calculated actual and predicted production based on the actual yields and harvested area, their trend lines and predictions for 2050, are shown in Table 3.The predictions look favorable based on the stated need for doubling the crop production by 2050 as a way to feed the increased world population, even with the increase in animal protein people will demand because of increased affluence.However, besides the concern about some of the available land suitable for cropping may not be profitable to farm due to lack of markets and infrastructure, there are also other concerns related to its availability, such as a need to preserve some areas where endangered wild animals live and breed.

Alternative Pathways
If the harvested area expansion ends up falling short of the predicted area as derived from the linear extrapolation, the question then is: "Is it possible that the yields can increase beyond what is predicted by the linear extrapolation for 2050?"Against this background, it is reasonable to expect that yields in Sub-Saharan Africa can be raised to the levels of yields in countries like Brazil and Argentina, given similar availability of high quality seeds, sufficient quantities of the necessary fertilizers, and efficient crop production technology.
Is it possible to double the crop production by 2050 if it is not possible to expand the harvested area by 600 million hectares as the predicted precondition if solely the yields predicted by the trend line projections for each region of the world come true?Is it possible to double crop production if the best practices and methods are broadly disseminated across the world and only half of the needed area is added or if the harvested area remains at the 2013 level?Table 4 seeks to shed light on that issue.By focusing on yield gains around the world for all crops, through dissemination of best seed genetics for each possible growing region, as well as adopting best practices and methods, including availability of the needed inputs to enhance and defend the yield potential, it is likely that the yield levels will be higher than indicated by the linear extrapolations out to 2050 for each crop and region.An estimate for what the production for each crop could reach by 2050 without any increase in harvested area and half the increase indicated by the trend line yield increases are shown in Table 4.The yields projected for 2050 by extrapolating the linear yield trend line for each crop in each region were ordered from highest to lowest.The two highest yielding regions were assigned the highest yield, the third highest yielding region was assigned the second highest yield, and regions with fourth-sixth highest yield were assigned the third highest yield.However, Sub-Saharan Africa were always assigned the predicted South American yield for each crop per the discussion above related to the available rain fall and climate zone being similar to the high yielding areas of South America.With this as the basis, it is clear from Table 4 that it is possible to increase the crop production by 134% without any increase in harvested area relative to 2013.By adding 300 million hectares to crop production in Sub-Saharan Africa, half of the increase in harvested area indicated in Table 2 would be realized, and it would then triple world crop production.

Sustainability of Crop Production Intensification
The intensification of crop production will have to be done in a way that the land base can sustain in the long run.Proposed methods and processes must leave the utilized resources in an equal or better condition over time to support continued use.The agricultural practices must conserve the land used for crop production and as a feed base for animal production, as well as be commercially viable (Gold, 2009;FAO, 2017).
Agricultural practices have evolved over the last three or four decades.Practices that focus on sustaining the soil have gained increased interest by farmers.Conservation tillage covers a spectrum of such practices and based on the key observation that crop residue left on the soil surface from the time of crop harvest until the following crop has emerged and beyond protects against wind and water soil erosion.
Proper erosion control often requires 30% or more crop residue cover immediately after planting of the subsequent crop.No-till leaves the soil undisturbed up until planting of the following crop (Nafziger, 2009).However, planting does disturb the crop residue to some degree, so in practice if at least 70% of the soil is covered with crop residue, then it is considered no-till.The effect of surface residue on soil erosion can be dramatic.Just 30% of the soil surface covered with plant residue after planting will reduce erosion by 50% compared to a bare field and 70% residue coverage will reduce erosion by 90% (Nafziger, 2009).
Growing cover crops in the period between two cash crops appears to be even more effective in reducing soil erosion.Laloy and Bielders (2009) reports that the soil erosion is reduced by more than 94% when cover crops are grown as compared to land left untouched with just the stubbles from maize harvest for silage.This indicates that the presence of a growing crop in the soil at all times has the potential to significantly reduce soil erosion over having just some amount of crop residue covering the soil surface between growing two cash crops.However, having crop residue covering the soil surface is better than bare soil in controlling erosion.According to SARE (2012), there are additional benefits associated with growing cover crops between two cash crops, such as increased soil health, reduced need, moisture conservation, and suppressed weed and disease infestations.
Sustainability of crop production can also be affected by when and how the field activities are executed and the specifications of the machines used.According to DeJong-Hughes ( 2001), wheel traffic is without a doubt the major cause of soil compaction, and some compaction can be beneficial in dryer years, but any degree of compaction is detrimental in wetter years.The threat of soil compaction is greater today because of the dramatic increase in the size of farm equipment (Duiker, 2004).Yield losses can be severe, up to 98% in the year of severe compaction in no-till conditions, but the soil will bounce back to yields of 85% in the second year without tillage and stabilize at around 93% after that relative to an uncompacted soil (Duiker, 2004).Schneider et al. (2017) reported that removal of root-restricting layers by a form of deep tillage generally resulted in a yield improvement of 20% relative to deep tillage of fields without a root-restricting layer.Soil compaction can be minimized by avoiding field work when the soil is too wet, by avoiding use of oversized machinery, and by practicing controlled traffic farming, CTF, where the same wheel tracks, or traffic lanes, are used by all machines year after year, leaving the remaining soil uncompacted (Wolkowski, 2008).

Discussion
The analyzed data and extrapolation thereof indicate that it is possible to raise crop production to the required level to feed the expected world population in 2050, even with an increase in demand for more animal protein in the diet by middle class people, which is expected to increase percentage wise as well.This prediction assumes that the expected yield increases materialize, and a sufficient portion of the stated available land suitable for crop production is brought into production, or that yield spread is reduced between regions of the world through widespread use of most appropriate seed technology for the region, fertilizers, crop production methods, and efficient machinery.
What are indicated as needed to achieve a doubling of crop production by 2050, can mostly be driven through the political process.It requires political action to put the infrastructure enhancements in place to increase access to efficient markets and low-cost energy, both liquid and gaseous fuels, and electricity.Access to sufficient financing required for acquiring the necessary modern farm machinery, as well as the needed crop production inputs, to attain the world level top yields, will likely require collateral, like assurance that the farm operator can prove ownership of the land that he farms.A policy change in countries where land ownership is not currently sanctioned might be necessary to gain access to the financial markets.Access to best seed technology and sufficient fertilizers suited for the local growing conditions will require trade among nations with limited restrictions, which again relies on political initiative to secure free access to foreign markets to buy and sell what is needed for crop production.In the case of accessing the best seed technology, it can be a question of honoring intellectual property rights between countries, which again requires political attention to be put in place, if it is not already the case.

Conclusions
A review of the worldwide top-five grain yield and area harvested trends and extrapolation of the trend lines indicate a doubling of crop production is possible by 2050.If the increase in area harvested is not allowed to increase to the extent indicated by the extrapolation of the trend line, then its effect on production can more than be compensated for by broad adopting of appropriate seed technology, equipment technology, best practices, and adequate access to fertilizers.Even a tripling of crop production is possible if half of the indicated increase in harvested area is also realized.This might require politically driven reforms in some areas of the world, where infrastructure and access limit efficient crop production.Increased farm machinery size is an additional threat to yield increases.Targeted use of large machines when the soil is capable of supporting them is indicated.Alternatively, Controlled Traffic Farming could be used to limit soil compaction impact on crop yields.
With higher degrees of automation of functions on modern farm machinery, the leap to full autonomy becomes smaller with time.Considerations should be made for what a machine system for crop production could look like and its potential impact on soil compaction, future yield and crop production sustainability.
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Table 2 .
Harvested area evolution for the period 1989-2013 and prediction for harvested area in 2050 in Mha

Table 3 .
World production of the top-five grains for the period 1989-2013 and prediction for production in 2050 in kT

Table 4 .
World production levels in kT by 2050 relative to 2005 & 2013 with focus on increasing yield and some or no increase in harvested area