Cassava Nitrogen Requirements in Thailand and Crop Simulation Model Predictions

Abstract

While cassava is an important crop in diverse regions of Thailand, little information is available to compare sites, select planting dates, and determine nitrogen (N) requirements. In recent years, the Decision Support System for Agrotechnology Transfer (DSSAT) has been used to develop this information. In order to use DSSAT, the cassava model, namely, CSM-CSCRP-Cassava, needs to be calibrated and validated. A cassava response to nitrogen study was conducted in Thailand during the 2011-2012 growing season. The data were also utilized to calibrate the DSSAT cassava model on cultivar Kasetsart 50. The model could be calibrated to predict the first branching date at 116 days, when it actually occurred at 117 days after planting. The overall average top dry weight and dry root yield were 7.39 and 15.69 t • ha −1 , which were predicted with a root mean square error of 0.496 and 0.702, respectively. Maximum leaf area index, leaf N (%), and harvested root N (%) were also adequately simulated. Validation experiments were conducted at the diverse Lopburi, Supanburi, and Chonburi sites. Top dry weight and dry root yield were predicted with indexes of agreement of 0.86 and 0.95 in Lopburi, 0.82 and 0.95 in Supanburi, and 0.83 and 0.55 in Chonburi. Nitrogen requirements for maximum yield were overpredicted by the model, indicating additional work is needed to account for negative effects of excessive N. Effects of regional weather conditions and soil types appeared to be adequately predicted by the calibrated model. Improved planting dates were suggested with the calibrated model.

Physiological determinants of storage root yield in three cassava genotypes under different nitrogen supply

“…Higher N fertilizer rates resulted in higher values for most crop traits in both the 2014/15 and 2015/16 growing seasons, indicating a positive effect of N fertilizer application on crop growth with both linear and quadratic functions. This result is similar to the report from Kaweewong et al (2013 a , b ), who indicated that N fertilizer influences cassava growth in certain production areas in Thailand and that increasing N fertilizer up to 250 kg/ha can increase above-ground biomass and storage root dry weights. Cruz et al (2003) reported that cassava grown under higher N-treatments (12 mM NO 3 – ) had higher photosynthetic capacities and SLA values than cassava grown under lower N-treatments (3 mM NO 3 – ).…”

“…However, storage root yield of cassava can be improved by using appropriate production technologies, such as planting with high-yielding cultivars, selecting suitable planting dates and applying adequate fertilizer rates. At present, many improved cassava cultivars are recommended for the production system in Thailand, and each cultivar responds and adapts differently to various management practices (Kaweewong et al 2013 a , b ). Nitrogen (N) fertilizer application is one of the most important management processes for increasing cassava storage root yield.…”

“…Previous studies have evaluated the responses of cassava to different application rates of N fertilizer and found that high rates can increase plant height, canopy width (Cenpukdee & Fukai 1991), number of leaves, number of storage roots, weight per storage root, final yield (Olasantan 1999), leaf N concentration (Nguyen et al 2002), chlorophyll concentration, chlorophyll a/b ratio, stomatal conductance, photorespiration rate, net carbon assimilation rate, specific leaf area (SLA) (Cruz et al 2003) and above-ground dry weight (Kaweewong et al 2013 a , b ). However, studies on the other physiological characteristics, such as crop growth rate (CGR), stem growth rate (SGR), leaf growth rate (LGR), storage root growth rate (SRGR), leaf area index (LAI), SLA and harvest index (HI) together with final storage root yields of different cassava branching types under different rates of N fertilizer applications are rare.…”

Chlorophyll fluorescence and biomass of four cassava genotypes grown under rain‐fed upper paddy field conditions in the tropics

“…During the dry season, some of the rain‐fed upper paddy fields are normally left fallow without planting for a period of 6–8 months due to a shortage of water resources. The cassava is amenable for growing under upland conditions throughout the year in Thailand (Kaweewong et al., ). It is resistant to drought conditions and can also be harvested from 6 until 24 months after planting, depending on growing conditions (El‐Sharkawy, ; Howeler, ; Howeler et al., ).…”

A Web application to estimate the climate change effects on agriculture in Thailand

“…Parameters for several of the rice cultivars grown in Thailand are provided in DSSAT because rice is an important crop all over the world. Parameters for the cassava cultivars grown in Thailand have been provided in research theses (Matthews and Hunt 1994;Sarawat et al 2000;Kaweewong et al 2013) because cassava is a major crop in Thailand. As we do not currently have parameters for vegetables, the default configuration (i.e., cultivar, dates and amounts of fertilizer and irrigation, and soil type) was used to execute the simulation, because local cultivating data were not available.…”