Fertilizer Application Efficiency Research Articles

Interpreting fertilizer use efficiency in relation to soil nutrient-supplying capacity, factor productivity, and agronomic efficiency

Although efficient use of N remains a critical constraint to productivity in irrigated lowland rice, a comprehensive database does not exist for the efficiency of on-farm management of N and other nutrients. In 1994, IRRI initiated its Mega Project on Reversing Trends of Declining Productivity in Intensive Irrigated Rice Systems in selected rice production domains of five tropical Asian nations to improve on-farm fertilizer use efficiency and to monitor long-term productivity trends as related to fertilizers and other inputs. Data are reported here for the first crop cycle, the 1994–95 dry season. The indigenous soil N supply (INS) was estimated by aboveground crop N uptake and grain yield (GY) in plots without applied N established in farmers’ fields under otherwise favorable growth conditions. The fertilizer N rate each farmer applied to his/her field surrounding these plots was recorded; GY was also measured in that area. In each domain, GY in unfertilized plots varied considerably among farms, as the range between maximum and minimum values within each domain was at least 2.8 t ha-1, thus of comparable magnitude to mean GY for these plots. Fertilizer N rates varied from 36 to 246 kg ha-1 across all domains, but their lack of relationship to INS contributed to relatively low fertilizer N efficiency and high variability in efficiency among farms. Mean agronomic efficiency (ΔGY/applied N rate) for each domain was only 6–15 kg grain kg-1 N, while values for individual farmers ranged from 0 to 59 kg grain kg-1 N. Initial data on P and K fertilizer management also suggest highly variable applications at suboptimal efficiency. These results indicate the potential for greater fertilizer efficiency from improved congruence between the indigenous soil supply and applied fertilizer and emphasize the need for field-specific nutrient management. Although agronomic efficiency and partial factor productivity (GY/applied N rate) can each be used to describe the efficiency of fertilizer applications, a complete analysis of nutrient management should include both terms, grain yield, fertilizer rates, and native soil fertility.

Recent improvements in the energy efficiency of agriculture: Case studies from Ontario, Canada

Energy used (GJ) per tonne of crop produced defines energy efficiency. Low energy use/tonne of crop produced indicates higher energy efficiency. Because of improved crop breeding (more stress tolerance, genetic gain) crop yields have increased. Concurrently, energy used has decreased. Based on an analysis of energy use/crop produced for Ontario's major row crops (corn and soybean), energy efficiency of crop production increased from 1975 to 1991. In corn, energy efficiency increased 49.8% from 87.95 l of diesel fuel equivalent (LDFE)/t of crop produced to 44.16 LDFE/t from 1975 to 1991. Total corn production (t) and yield (t/ha) increased by 60.0% and 20.1%, respectively, whereas energy use/ha (LDFE/ha) and total energy use (LDFE) decreased by 39.7% and 19.7%, respectively. For soybean, energy use/ha (LDFE/ha) decreased by 46.3% but total energy use (LDFE) increased by 93.8%. The increase in total energy use was caused by a 260.8% increase in soybean acreage (ha). Because the increase in soybean production (t) of 278.2% was much greater than the increase in total energy use (LDFE), energy efficiency increased 48.7% from 75.46 LDFE/t to 38.67 LDFE/t. The proportion that fertilizer manufacturing contributes to total annual energy use in corn decreased slightly (74.2–71.0%) between 1975 and 1991; however, energy use in fertilizer manufacturing declined by 42.4% because of the increased efficiency of manufacturing nitrogen fertilizers. Increased efficiency of fertilizer application also decreased energy use, although application is a much smaller proportion of the total energy use budget. Similar decreases occurred in soybean production. Our analysis of no-till systems using various herbicides and application rates indicated that the systems using the highest herbicide application rates required the least energy, because decreased herbicide application rates may require increased cultivation. This, however, depends on the timing (pre-plant, planting, post-emergent) and type (banded, broadcast) of application and is true only for newer herbicides with low application rates.

Effects of fertilizer price on feasibility of efficiency improvement: Case study for an urea injector for lowland rice

Efficiency improving techniques, such as the introduction of a urea injector for lowland rice production, appear to lead to higher yields, lower fertilizer use and less environmental pollution at the same time. If farmers are free to decide on the amount of fertilizer they use, economic rationality leads to a choice between using the improved technique for saving fertilizer while obtaining the same yield, for increasing yield (at the same fertilizer rate) or for a mixed strategy (a slightly higher yield and a different fertilizer rate). The ‘economic optimum fertilizer rate’ was calculated with a simple yield model for a low and a high fertilizer application efficiency to predict which strategy would be best for the farmer. Calculations for a ‘standard’ data set for lowland rice show that the greatest benefit from an increase in application efficiency by urea deep placement instead of broadcast application can be expected when a marginal efficiency of about 9 kg rice per kg fertilizer N is used for determining the fertilizer rate. For a marginal efficiency of less than 6, savings on fertilizer are the main benefit of efficiency improvement; for higher marginal efficiencies yield increases become the main component of total benefit; for marginal efficiencies above 9, fertilizer use will increase when a more efficient technique is used, but increased yields compensate for their costs. In the four countries where a manually operated pneumatic urea injector was tested (Togo, Bangladesh, Indonesia and Ivory Coast) the price ratio of rice and fertilizer N ranged from 1.1 to 2.5. Even when a ‘risk-avoidance’ multiplier of 2 is used, we may conclude that fertilizer prices were too low relative to rice to make optimum use of the existing techniques for efficiency improvement. An equation is derived for estimating the price ratio at which the probability of farmer acceptance of techniques for improving fertilizer use efficiency is highest.

NPK-fertilizer efficiency — a situation analysis for the tropics

This paper examines the efficiency of applied N, P, and K fertilizers under tropical conditions. To meet their food demands, tropical countries are importing large quantities of fertilizers at an enormous cost. There is a need for improving crop yields at a reduced cost and a better understanding of the factors that contribute to the overall efficiency of applied fertilizers. It is estimated that under tropical condition, the efficiency of applied N is less than 50%, less than 10% for P and for K it is somewhere around 40%. Losses of N are mainly due to leaching, runoff and volatile losses of ammonia. Under flooding and in alternate wetting and drying conditions of rice lands and low lands, dentrification and volatile ammonia losses are considerable. The N losses from these soil could be minimized by proper management such as rate, methods and time of application. The coating of urea with S has shown some improvement in increasing efficiency. Nitrification and urea hydrolysis inhibitors can improve fertilizer efficiency in certain situations provided they are properly used. The efficiencies of these inhibitors depend on the nature of the chemical compounds, soil properties, and method of application. Low efficiency of applied P fertilizer is mainly due to retention of P by soil clay fractions and iron and aluminum hydroxides. Even though retained P is not available to the first crop, it is made available to a certain extent to the succeeding crops. The rate and methods of P applications and forms of P determine the efficiency of applied P fertilizers. The use of native rock phosphate along with P fertilizers on acid soils appears to be an attractive alternative in reducing the fertilizer cost. The loss of K in tropical soils is largely attributed to leaching and runoff. To reduce K loss by leaching, it is more advisible to apply K in split doses than a single dose. Liming has a beneficial effect in retention of K and reducing P fixation in acid soils.

Utilization of Tracer Nitrogen by Rice in Relation to Time of Application1

AbstractUptake of N16 tagged ammonium sulfate by rice plants was used to evaluate the efficiency of fertilizer applications. Two‐thirds of the basal rate at planting followed by one‐third top‐dressed at boot stage resulted in the highest recovery of fertilizer nitrogen as compared to the full rate at planting or top‐dressing at the tillering stage.