Soil response to impacts of pesticide and fertilizer over time

Lazarus Dawa

University of Sriwijaya, Palembang, Indonesia
Email: ldawa@live.com.au
September, 2013

Introduction

The world population had increased at annual rate of 1.76 from 1950 to 2000 and it was predicted for the next 50 years the average growth rate will be at 0.77 percent per annum (UN,2004).  This directly implies that the current demand for food and meat products will increase and the land and environment must be utilized to meet these growing human needs. In addition to population growth, increase in income and changes in diet pattern especially to more livestock products consumption will also be the main drivers of increase food production (FAO, 2012).  In order to produce more food, the agriculture practices have to be adjusted to increase production quantity.  Land is under pressure from increase human activities and there will be competition for land use for infrastructure development and other non-food uses versus agriculture utilization.  Decrease in land available for agriculture and deterioration of soil quality from continuous cultivation will require intensification process to grow crops by utilizing fertilizers, pesticides, irrigation and other technologies.  Over use of fertilizers and pesticides can have negative effect on soil qualityies.  Application of nitrogen fertilizer in wheat and rice over period of 20 years was found to reduce yield in both crops (Kumar & Yadav, 2001).

Therefore to maintain long term sustainability and productivity of the soil, it is better to choose the best practice of applying fertilizers and pesticides while ensuring food productions are still maintained.
The purpose of this paper is to discuss the various impacts of continuous fertilizer and pesticide use on the soil quality over time.  It will also extend to suggest some of the best options that can be taken to reduce the negative impact of fertilizer and pesticide on the soil.

Effect of pesticides on soil

Pesticides refer to any substance or mixture of substances intended to control, inhibit or destroy any pests that interfere with crop production.  The use of synthetic pesticides has both beneficial and negative effects.  The primary benefit of pesticide use is protection of crops from diseases and pests which reduce losses and preserve crop yields.  Pesticides if manage and use efficiently is safe however over use of it can cause health hazards, interfere with soil and natural bio-ecosystem which can impede food production.
Pesticides use are known to affect soil microorganisms which carry out important soil function such as decomposition of organic matter, supplying of nutrients to soil and maintaining soil structure.
It was found that fumigation of soil with commercial isothiocynate (ITC) based fumigant (metham sodium) had inhibited microbial activity, reduced biomass of all microbial groups and create consistent changes on the structure of the ascomycete community (Omirou et al, 2011).  Ascomoycetes fungus is important for biodegradation process of organic matter through secretion of enzymes that act on degradation of lignin in woods of dead plants (Martinez, et al 2005).  When ascomycetes population in soil is lowered, the degradation process of organic matter will be slowed thus affecting the nutrient profile of the soil especially in terms of carbon and other minerals like phosphorous and nitrogen which are released from the humus as it decay.

While Ahemad and Mohammad (2012) study on rhizobium bacteria exposed to pesticides stress showed reduce production of plant growth producing substance.  The rhizobium bacteria are group of organisms that live freely in soil and colonize the root.  They are usually referred to as plant growth promoting bacteria (PGPR).  The PGPR operate by synthesizing of particular compounds for the plants, facilitates uptake of certain nutrients from the soil and lessening or preventing the plants from disease (Hayat et al, 2010).
Increasing concentration of arsenic pesticide use in soil decrease biomass, shoot height and root length, all of which are important traits of showing plant growth (Quazi et al 2011).  Arsenic being one of the non-essential substance for plant growth, it interferes with metabolic process and inhibit plant growth and death at high concentration.

Effect of fertilizers on soil

Chemical fertilizers are key inputs to increased agricultural food production.  The overall world food supply has been sufficient to meet the population need, the global average per capita food available for direct consumption was 2770 kilo calories/person/day in 2005 and 2007. It is also projected that fertilizer use will increase from 166 million tonnes in 2005 and 2007 to 263 million tonnes in 2050.    Much of this achievement in general food production can be attributed to the use of fertilizers and developing countries account for 70 percent of global fertilizer consumption (FAO, 2012).  Fertilizers improve and buffer soil fertility by providing essential nutrients such as nitrogen, potassium, phosphorous, and other minerals which the plant needs to sustain growth and production. Although increased fertilizer use will boost crop production, it is also crucial here to identify some negative impact of continuous fertilizer application on the soil health.

Continuous cropping with nitrogen fertilizer application for 25 years in acidic soil was found to reduce the yield of maize and wheat significantly.  The use of nitrogen fertilizer alone had greater impact on reducing soil pH from pH of 5.8 to 4.7 during that period. (Sharma & Subehia, 2003). Nitrogen fertilizers are not acidic but are acid forming due to the presence of ammonia group (NH4) the ammonia oxidizing arachea and ammonia oxidizing bacteria in the soil converts the ammonia to nitrite and then to nitrate by nitrite oxidizers (Alam et al, 2013).

Soil pH is an important aspect of agronomy since it dictates the response of metal ion solubility and availability of nutrient to the varying pH level.  When soil pH is low below the neutral point of 7, the metal ion become more soluble and there is increased tendency of uptake by plants which can lead to mineral toxicity where as some nutrients are bounded in acidic conditions depriving the plants from its nutrients demand.  The response to declining pH level varies among crop types.  For example corn grows in pH between 5.8-7.0, wheat from 6.3-7.0 and cowpea can grow between pH 5.5-7.0.
In long term cropping observation, applying of only nitrogen fertilizer had no increase effect on the soil organic carbon level (Liu et al, 2013).  Organic carbon in soil is a reliable indicator of the state of soil organic matter which the latter is important for improving the soil physical and biological properties to sustain crop production.

Practices to improve soil quality

Based on the few reviewed study on impact of fertilizer and pesticides use on soil which in turn determines the crop health and growth it is important to identify and promote good agricultural practices that is beneficial to the soil as well as the surrounding ecosystem.

1. Altering pesticides and fertilizer usage
Soil quality can be improved by changing the agricultural practices that involve use of fertilizers and pesticides. As observed, it can be seen that use of only one fertilizer affect soil quality and by combining more than one fertilizer can alleviate the negative effect of continuous fertilizer use.  Integrated nutrient management by combining manure and inorganic fertilizer has shown to improve soil organic matter in degrading agriculture land (Liu et al, 2013).  This will provide long term sustainable food production and also contribute to reducing of green house gases from nitrogen fertilizer use.

2. Organic farming
Organic farming represents a promising solution to maintain current soil quality while meeting world food demand.  Shifting from conventional to organic farming eliminates the need for fertilizer and pesticides by utilizing organic means such as manure, cover crops and biopesticides.  In that way, many negative impacts of chemical inputs can be reduced and allow for natural cycles to occur.  Although the question of whether organic farming can meet future food demand exist, a study by Badgley et al (2006) showed that organic farming could produce enough food to meet the current and even expanding world population without increasing the land area. It was also found that leguminous cover crops could produce enough nitrogen to replace the amount of synthetic nitrogen fertilizers currently in use.

Conclusion
The need to feed the world in the next 20 years will depend largely on soil and water availability and qualities.  It is important that these resources must be used in sustainable way by limiting use of chemicals.  Some pesticides are known to affect soil microorganisms that are beneficial to soil health in sustaining plant growth. Fertilizer overuse can also decrease soil quality which creates the problem for the soil to be more reliant on fertilizer and continuous use can eventually lead to unproductive soils.  By date, organic farming remains the best options for long term food production and preservation of soil.

ADAPTIVE AND MITIGATING APPROACH TO EFFECT OF CLIMATE CHANGE ON FOOD SECURITY IN PAPUA NEW GUINEA

Lazarus Dawa

University of Sriwijaya Palembang, Indonesia

Email: ldawa@live.com.au

September 2012

I. INTRODUCTION

Climate change has been discussed as one of the most important factor that will impact food security, leading to increase number of hunger people and malnutrition as a result of collapse food system. Food production will become a challenge for the world to achieve under adverse changing environmental conditions, increasing population pressure and degrading land and natural resources. Papua New Guinea will be greatly affected because more than 80 percent of the population are subsistence farmers who rely on food gardens, forest and ocean or waters for their daily food needs. In order to adapt to the effect of climate change while ensuring sufficient and quality food is available and accessible to every household at all times, appropriate approaches are needed by each government and relevant stakeholders involved in working towards securing resilient livelihood system for the people.

Factors contributing to climate change

Human activities have been one of the biggest contributing factor of climate changes by altering the composition of the atmosphere.  Continued realease of green house gases (methane, carbon dioxide, nitrous oxide and halo carbons) into the atmosphere has cause the earths temperature to increase resulting in the event of global warming.  The main activities that leads to increase in GHG into the atmosphere has been due to the burning of the fossil fuels to meet energy demands, land use for agricultural activities for the food production, and deforestation (FAO, 2008a).  The manifestation of climate change can be observed by the increase surface temperature of earth by 2-40C, increase level of  carbondioxide  in  the  atmosphere,  varying  rainfall  patterns  and  precipitation,  longer  drought periods, extreme weather conditions such as cyclone and floods and change in the ecosystem.

Climate change in the pacific

Papua New Guinea is one of the Pacific island nation facing vulnerability to climate change such as cyclone, drought, rising sea  level  and  flooding. Majority  of  the  population  depend  on subsistence farming for their livelihood by using the surrounding natural resources for their food and source of income.   In 2011, islanders in Nissan, Carterets and Mortlock experienced food shortage in which approximately 6000 people were in need of food assistance (IRIN, 2011).  This event occured after extended dry season causing drought and loss of food and water for the islanders. Climate change will have severe repercussions on the livelihood of the people in the absence of any effective govenment intervention that will aim to achieve and improve resilience to food security under climate change condition.  Planning and implementing programs that will mitigate the effect of climate change and long term adaptability strategies are essential steps contributing to efforts on reducing emission of GHG and ensuring food security.

II. EFFECT OF CLIMATE CHANGE ON FOOD SECURITY

Food Availability

Climate change will have negative effect on food crop production, livestock and fisheries sectors. Food crop production is very susceptible to climate change and it was estimated that it will reduce crop yields. There will be varying rainfall patterns resulting in heavier precipitation than usual and longer extended drought periods in the tropics.   Food crops seasonal production will be affected and reduce yield as plants become intolerant to longer drought and wet seasons.   Crop modeling studies under climate change showed that in the tropics average temperature increase of 1-2oC will have negative impact on crop production (Tubiello et al, 2008)

Animal production will be affected by climate change as temperature increase can cause heat stress to the animals which interfere with their physiological process, health and reproduction.  Indirectly when climate change reduced capacity for food production, animal nutrition will be in short supply and therefore prevent them from reaching full growth potential.

In the fisheries sector especially catch fisheries, fish production capacity will not be influence by climate change but it will affect the spatial distribution of the fish in the ocean.  Increase in water temperature will cause migration of the fish to more cool part of the ocean where it is favorable.  Fish and other marine life will be at risk of loss due to build up of carbon dioxide in the atmosphere.  The capacity of the ocean to absorb CO2 with any detrimental effect to marine life is about 30%, however increased emission of green house gases will lead to rise in level of CO2  in the ocean which are converted to carbonic acid causing death of coral reef.

Food accessibility

Food accessibility refers to the ability of the household to have means either physical or economic means to have food for their daily consumption.  Household who rely on farming as their ways to earning income and providing food will experience less income and few foods available to meet their needs as land and environment become unsuitable for their crop or animal production.  A decrease in food production will cause price of food to escalate, reducing the purchasing power of poor household and hindering them from access to enough for their consumption.

Food utilization

Food security is vital in achieving good nutrition status.  Climate change has been predicted to have negative consequences on fullfilling the required nutritional needs of people if the availability and accessiblity to food is reduced.  The number of malnourished children and woman who are vulnerable will be at stake of disease and increase chances of mortality.

Climate change will increase incidence of food borne diseases due to changing patterns of food pathogens and altering of the environment that result in the imbalance in the microbial ecosystem.

Food handling and preparation hazard assessment need to be reviewed to identify new risk that emerged as impact of increase global surface temperature.   Food industries will need to reorientate their food safety systems to prevent food borne disease outbreak that may result due to climate change effect.

Cholera outbreak is termed as one of the good scenario to understand the effect of climate change on food borne disease outbreak.The outbreak reach high levels was found to be related to increase water temperature (FAO, 2008b).  Another example of climate change on food borne disease outbreak was studied between the hospitalization of children due to rotavirus infection, following periods of high  temperature and humidity,  there  was decreased  rate  of  hospitalization in  children  observed (D’Souza et al, 2008).  The study therefore showed that rotavirus is less tolerable to high temperature but favors low temperature.

Stability of the system

The constant access and availability of sufficient and nutritious food by every household is important to achieve food security.   If food production decline and on the supply side there is insufficient quantities of food availble to meet the demand, then food system stability will be difficult task to achieve.

III. MITIGATION AND ADAPTATION

Mitigation approach refers to methods that are needed to reduce the emission of green house gases and other land use activities that contribute to climate change. Adaptation is based on the approach that are necessary to optimize safe, nutritious and sufficient food supply and accessiblity in the era of climate change.  

Mitigating approach

Land use change for agriculture activity contributes to increase in green house gases.  Clearing of new lands for agriculture activities reduce the area of forest available for sequestring of CO2.   In additon opening of wet lands for crop cultivation release methane gas to the atmosphere.  Land tillage, use of nitrogen fertilizers are contributing factors to GHG emissions as well.   Management of crop land through appropriate practices provide possible mitigation solution towards effort on reducing of GHG. Intensification of the already cultivated land to optimize agriculture output without need for more new land openings.  Farming with perenial crops provide cover for soil from erosion, capture the carbon stock and form part of the agro forestry system.

Ongoing logging activities, clearing of lands for cash crop and food crops production has led to decrease conversion of carbon dioxide in the atmosphere.   Efforts to increase of forest area from unused land as well as increasing carbon density of existing forest present better option for mitigating climate change. 

Papua New Guinea forest covers is the third in the world.  According to Green peace (2012), over 60 percent of the forest has been exploited by logging and agriculture activity already. Issues of illegal logging and lease of land for agriculture uses has been stated by World Bank and UN as a threat to the existing forest sustainability.  Since PNG has been part of the signatory to the Kyoto

protocol in reducing GHG it is the government responsibilities to regulate logging in a sustainable way and ensure transparency in leasing permit for agriculture and logging activities.

Following the Kyoto protocol in 1997, use of the ecosystem as carbon sequesterants was suggested as one of the way forward for nations to adapt and implement as global efforts towards mitigation of GHG. 

Carbon sinks in the soil and plants can be used to absorb carbon dioxide in the atmosphere through recommended soil management practice.  The benefits to soil is attain as carbon compounds in the soil is restored, which improves soil quality and optimize land for crop production.

Adaptive actions

The adaptive approach to be taken by the government or concerned groups to ensure food supply is consistent despite climate changing will be discussed here.

Identifying better technology to produce, preserve and distribute food will contribute to ensuring food security.   Development of new crop varieties tolerable to the climatic changes such as drought or rainfall are innovative prospects in the agriculture sector to keep up with the food production. Establishment of irrigation system for farmers is essential intervention when rainfall patterns become less which can cause huge loss to crops.  Upgrading of current infrastructure and storage facilities for distribution of crops from the producer to the consumers remain an issue in PNG, due to rough geographical condition of the land.  If a better market supply chain for food commodities exist food shortage in one region can be relieved through inter state or regional food exchange.   Achieving technological solution for food security adaptation in condition of climate change will require investment from both the government and private sectors.

Review of the current hazard assessment plan and identifying of new risks present in the food system are possible actions that can provide assurance that the food are safer for the population.

In  order  to  prevent the  loss  of  food  and income  due  to  climate  change,  programes  aimed  at improving food security could focus on diversification of income and food sources.  If a major means of earning income is not possible or food crops fail then people can easily transition to another options to sustain their living especially diversifying to non agricultural activity.

Government investment into safety nets program is important to assist households who experienced loss of income or less food access during the event of climate change.  Social safety nets programs need to be established and requires government reserving of funds for that purpose before the shock eventuates.

To summarize food security remains an important agenda for any government of the day. Prior planning and channeling of resources towards preparation of resilience system from effect of climate change are best decisions forwards as well as taking part in global action on reducing and sequestering of green house gases. Papua new guinea has a large rural base population whose livelihood are earned through subsistence farming, which place them in a vulnerable position to effect of climate change.