Increasing global crop harvest frequency: recent trends and future directions

Abstract

The world's agricultural systems face the challenge of meeting the rising demands from population growth, changing dietary preferences, and expanding biofuel use. Previous studies have put forward strategies for meeting this growing demand by increasing global crop production, either expanding the area under cultivation or intensifying the crop yields of our existing agricultural lands. However, another possible means for increasing global crop production has received less attention: increasing the frequency of global cropland harvested each year. Historically, many of the world's croplands were left fallow, or had failed harvests, each year, foregoing opportunities for delivering crop production. Furthermore, many regions, particularly in the tropics, may be capable of multiple harvests per year, often more than are harvested today.Here we analyze a global compilation of agricultural statistics to show how the world's harvested cropland has changed. Between 2000 and 2011, harvested land area grew roughly 4 times faster than total standing cropland area. Using a metric of cropland harvest frequency (CHF)-the ratio of land harvested each year to the total standing cropland-and its recent trends, we identify countries that harvest their croplands more frequently, and those that have the potential to increase their cropland harvest frequency. We suggest that a possible 'harvest gap' may exist in many countries that represents an opportunity to increase crop production on existing agricultural lands. However, increasing the harvest frequency of existing croplands could have significant environmental and social impacts, which need careful evaluation.

Sustaining food self-sufficiency of a nation: The case of Sri Lankan rice production and related water and fertilizer demands

“…In much of the country, rice yields are already approaching Mueller et al (2012)'s estimated maximum attainable yield of 5 tons ha -1 . The frequency with which rice has historically been harvested in Sri Lanka has remained stable at *1.1 harvests year -1 over the past 30 years, a value well below the maximum possible harvest frequency of 2 harvests year -1 estimated by Ray and Foley (2013).…”

“…Nevertheless, confounding socioeconomic (e.g., infrastructural maintenance and labor costs) and biophysical (e.g., climate extremes) factors likely make this option less viable (Ray and Foley 2013). Currently, 90 % of the total water withdrawals in Sri Lanka are used for agricultural purposes (FAO 2014b) and rice comprises one-third of Sri Lankan crop production (FAO 2014a).…”

“…Crop harvest frequency for temporary crops (i.e., crops that must be planted every growing cycle) was calculated for each year by dividing the harvested area for temporary crops by the arable area for temporary crops (FAO 2014a) following the methods of Ray and Foley (2013); this ratio was found to be consistent at 1.1 harvests year -1 over the past 30 years. Maximum potential harvest frequency for temporary crops (i.e., 2 harvests year -1 ) was determined by Ray and Foley (2013); maximum and current harvest frequencies for temporary crops were assumed to be the same for rice because rice production comprised 82 % of temporary crop production (FAO 2014a). We also assumed a linear relationship between harvest frequency and resources for the scenarios considered here (e.g., if harvest frequency doubles for a given yield, then the amount of required resources also doubles).…”

Global change pressures on soils from land use and management

“…The global harvested area (i.e. counting each time an area is harvested) increased four times faster than total cropland area between 2000 and 2011 (Ray & Foley, 2013). The fraction of net primary production (NPP) extracted by humans is increasing (Haberl et al, 2007).…”

Sustainable commercialization of new crops for the agricultural bioeconomy

“…While widespread integration of pennycress into summer-annual crop production systems would certainly add diversity, it is possible that the net effect might be seen by these stakeholders as only an incremental improvement, involving a fallow-season "monoculture" of sorts. In addition, other potential effects of extensive pennycress cultivation that may arouse sustainability concerns include invasiveness, effects on pest dynamics, e.g., via by providing a winter host for diseases (Smith et al, 2011), and effects of possible increases in agrochemical inputs (Ray and Foley, 2013). For example, e.g., unintended effects on pollinators may result from neonicotinoid pesticide residues (Budge et al, 2015).…”