N release curve of CRF was divided into the sigmoid pattern, parabolic pattern, and double parabolic pattern (Yu et al., 2006). A CRF whose CNR (from a CRF) curve has a parabolic shape is called a PCRF, but if the curve is sigmoidal or “S” shaped, the CRF is called a SCRF. These two CRFs have different release mechanisms and coating processes used during manufacturing. Formerly, PCRFs were used almost exclusively throughout the world. Accurate evaluations of the characteristics of N release from PCRFs are important for selecting a suitable release pattern of PCRF that is matched to the needs of the developing vegetable crop for optimal and efficient N uptake, greater yields, and reduced losses of N to the environment (Carson and Ozores-Hampton, 2012). Over the past 50 years, several PCRF coating technologies have been developed and marketed, and several methods to predict CNR release from these CRF technologies have been developed for regulatory purposes including 1) laboratory or growth chamber, 2) greenhouse, and 3) field (Carson and Ozores-Hampton, 2012); however, one method of CNR prediction has yet been selected for regulatory purposes in China and some other countries (Carson et al., 2014b; Fujinuma et al., 2009; Sartain et al., 2004a, 2004b).
Laboratory methods include a standard method (Dai et al., 2008; Du et al., 2006; European Committee for Standardization, 2002), and the accelerated temperature-controlled incubation methods (ATCIMs) (Dai et al., 2008). The earlier mentioned standard method is involved in the incubation of PCRFs, which requires the use of selected time periods, temperatures, and/or sampling methods. Compared with the standard method, ATCIMs are used with shorter incubation periods, which reduce time and labor costs. However, these two methods may be used to predict release rates in the laboratory but—by themselves—they are not able to accurately predict release rates in the field (Carson and Ozores-Hampton, 2012).
Growth chamber and greenhouse methods—which include incubation in columns and plastic bags—may be used to test PCRF products under conditions that are fairly similar to those in a particular crop production system (Abraham and Rajasekharan Pillai, 1996; Broschat, 1996; Broschat and Moore, 2007; Sato and Morgan, 2008). The column method predicts CNR from PCRFs more accurately than the plastic bag method because ammonia volatilization and lower N recovery rates are associated with the bag method (Carson and Ozores-Hampton, 2012). During PVC-column laboratory incubation, release of PCRFs at a constant temperature and moisture content are determined by leaching the released N with minimal variability of incubation conditions compared with PCRFs placed in the very variable conditions of open fields (Carson et al., 2014b). Indeed, field studies are subject to diurnal temperature oscillations, variable weather patterns, and water table fluctuations (Medina, 2011). Incubation temperatures in growth chambers or greenhouses—especially greenhouses that lack precise temperature controls—tend to be more similar to soil temperatures in open fields than the testing temperatures specified by manufacturers (Carson and Ozores-Hampton, 2012).
Pot-in-pot and pouch methods are two viable field methods for evaluating PCRFs in vegetable crop production research. The pouch method—whereby water-porous pouches with PCRF prills are placed within or under vegetable beds and later recovered at predetermined times throughout the growing season—measures CNR by calculating the N remaining in the PCRF prills. In contrast, the pot-in-pot method—whereby the covered upper pot with a screened bottom and filled with soil from the field and mixed with PCRF prills is nested in the water-tight lower pot from which leachate is collected periodically after application of water to the upper pot—measures the instantaneous amount of N release leached directly from the PCRF. In any case, it is important to consider that environmental conditions in greenhouse plots and open fields are very variable, and that release rates of PCRFs depend strongly on soil temperatures. PCRF prills must meet the needs of the crop as it is influenced by fluctuating soil temperatures throughout all growing seasons and over multiple years (Fraisse et al., 2010).
Therefore, it is necessary to integrate the use of laboratory, growth chamber, and field methods into a single protocol for characterizing the performance of PCRFs under a wide range of conditions encountered in commercial vegetable production. A correlation between an ATCIM and the pouch method was developed using a two-step process in tomato, Solanum lycopersicum L. (Solanales: Solanaceae), production in Florida (Carson et al., 2014a). Japanese researchers established a model to predict CNR using field temperatures in an experiment in a rice field (Zhang et al., 2008).
Characterizing the performance of PCRFs involves a range of factors under field conditions, such as release time, temperature, moisture, placement, microbial action, and cultural practices. However, soil temperature may be considered the most influential factor influencing N release from PCRFs in greenhouse plots with irrigated vegetables (Carson et al., 2013; Fujita, 1989; Fujita et al., 1983).
The objective of this study was to develop and validate a model to accurately predict the N release characteristics of various PCRFs under the conditions of commercial vegetable crop production in nontemperature-regulated greenhouse plots. The approach to achieving this objective was to evaluate correlations between N release rates and soil temperatures as determined by use of a temperature-controlled incubation method and a field pouch method, to develop a predictive model based on a first-order N release equation that was valid under a relevant range of constant temperatures, and then to modify this equation to extend its usefulness to N release from PCRFs under fluctuating temperatures. We postulated that the latter step could be achieved by using the activation energy of the N release reaction to elucidate the relationship between the N release rate and the natural field temperature. The overall purpose of this effort was provide a useful predictive tool to assist growers and manufacturers to easily select PCRFs with the correct N release rates that match the needs of vegetable crops throughout the production process to assure efficient use of fertilizers, minimal off-site impacts, and lower economic costs.
AbrahamJ.Rajasekharan PillaiV.N.1996Membrane-encapsulated controlled-release urea fertilizers based on acrylamide copolymersJ. Appl. Polym. Sci.6023472351
AgeharaS.WarnckeD.D.2005Soil moisture and temperature effects on nitrogen release from organic nitrogen sourcesSoil Sci. Soc. Amer. J.6918441855
Beijing Municipal Bureau of Statistics2015Beijing statistical yearbook. China statistics press Beijing China. 20–50 (In Chinese)
BroschatT.K.MooreK.K.2007Release rates of ammonium-nitrogen, nitrate-nitrogen, phosphorus, potassium, magnesium, iron, and manganese from seven controlled-release fertilizersCommun. Soil Sci. Plant Anal.38843850
CarsonL.C.Ozores-HamptonM.2012Methods for determining nitrogen release from controlled-release fertilizers used for vegetable productionHortTechnology222024
CarsonL.C.Ozores-HamptonM.MorganK.T.2013Nitrogen release from controlled- release fertilizers in seepage-irrigated tomato production in south FloridaProc. Annu. Meet. Fla. State Hort. Soc.126131135
CarsonL.C.Ozores-HamptonM.MorganK.T.SartainJ.B.2014aNitrogen release properties of controlled-release fertilizers during tomato productionHortScience4915681574
CarsonL.C.Ozores-HamptonM.MorganK.T.SartainJ.B.2014bPrediction of controlled- release fertilizer nitrogen release using the pouch field and accelerated temperature-controlled incubation methods in sand soilsHortScience4915751581
CarsonL.C.Ozores-HamptonM.SartainJ.B.2012bControlled-release fertilizer drying methods effect on nitrogen recovery analysisHortScience47S320
DaiJ.J.FanX.L.YuJ.G.LiuF.ZhangQ.2008Study on a rapid method to predict longevity of controlled release fertilizer coated by water soluble resinAgr. Sci. China711271132(In Chinese)
DeansJ.MolinaJ.ClappC.1986Models for predicting potentially mineralizable nitrogen and decomposition rate constantsSoil Sci. Soc. Amer. J.50323326
DuC.W.ZouJ.M.ShavivA.2006Release characteristics of nutrients from polymer-coated compound controlled release fertilizersJ. Polymers Environ.14223230
European Committee for Standardization2002Slow-release fertilizers: Determination of the nutrients-method for coated fertilizers. EN 13266:2001. European Committee for Standardization Brussels Belgium
FraisseC.W.HuZ.SimonneE.H.2010Effect of El Nino-southern oscillation on the number of leaching rain events in Florida and implications on nutrient management for tomatoHortTechnology20120132
FujinumaR.BalsterN.J.NormanJ.M.2009An improved model of nitrogen release for surface applied controlled-release fertilizerSoil Sci. Soc. Amer. J.73620432050
FujitaT.1989Invention and development of polyolefin-coated urea. Ph.D.dissertation. Tohoku Univ. Sendai Japan
FujitaT.TakahashiC.YoshidaS.HimizuH.1983Coated granular fertilizer capable of controlling the effects of temperature on dissolution out rate. U.S. Patent 4369055. 18 Jan. 1983
MedinaC.2011Method development to characterize nutrient release patterns of enhanced efficiency fertilizers. Univ. Florida Gainesville FL PhD Diss
SartainJ.B.HallW.L.LittellR.C.HopwoodE.W.2004aDevelopment of methodologies for characterization of slow-release fertilizersProc. Soil Crop Sci. Soc. Fla.637275
SartainJ.B.HallW.L.LittellR.C.HopwoodE.W.2004bNew tools for the analysis and characterization of slow-release fertilizers p. 180–195. In: W.L. Hall and W.P. Robarge (eds.). Environmental impact of fertilizer on soil and water. American Chemical Society Washington DC
SAS Institute2011SAS/STAT 9.3 User’s Guide. SAS Inst. Cary NC
SatoS.MorganK.T.2008Nitrogen recovery and transformation from a surface or sub-surface application of controlled-release fertilizer on a sandy soilJ. Plant Nutr.3122142231
YangJ.G.NiX.H.CaoB.XiaoQ.ZouG.Y.LiuB.C.2014Effect of special controlled-release fertilizer application on nitrogen and potassium uptakes of tomato and their residue in soil with drip-irrigation in the green-houseJ. Plant Nutr. Fert.20512941302(In Chinese)
YuJ.G.FanX.L.LiN.LiuF.2006Application of the richards equation to describe nitrogen release characteristics from controlled release fertilizer (CRF)Zhongguo Nong Ye Ke Xue39918531858(In Chinese)
ZhangY.L.ZhangY.L.DangX.L.YinW.S.ZhuL.P.2008Prediction on the dissolving rate of nitrogen from coated urea by days of temperature switchChin. J. Soil Sci.393582585(In Chinese)
ZouL. Q.2010Principle of least square method and its simple application. Science & Technology Information 23:282–283. (In Chinese)