Técnicas de diagnóstico para la recomendación de fertilización nitrogenada en el cultivo de maíz en el valle medio del río Yaracuy del Estado Yaracuy
More of the Venezuelan soils shown problems associated to soil degradation and low N availability. In the medium valley of the Yaracuy river, just like all aroud the country, N dose are required for maize, and normally it is estimated from crop response to N application in experiment carried out som...
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2014
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| Accesso online: | http://hdl.handle.net/10872/7531 |
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| Riassunto: | More of the Venezuelan soils shown problems associated to soil degradation and low N availability. In the medium valley of the Yaracuy river, just like all aroud the country, N dose are required for maize, and normally it is estimated from crop response to N application in experiment carried out some years ago for different some conditions and hybrid and variety of the crop. To estimate N dose for maize none of the soil parameters associated to N availability are taken in account. In this study we evaluated some methods to diagnostic soil N availabity and N dose required: 1) Soil N availability extracted by KCl (2M) at the sowing time and a the V5-V6 stage (25-30 days after sowing time), 2) use of a clorofilometer (SPAD reading) measured a the V5-V6, V10-V11, and R1 crop stage, 3) the NuMASS program which is an expert system support for N, P, and lime dose recommendation, and 4) a simulation model named INIA which is based in some of the principal soil, crop, wether and management characteristics for N dose recommendations for maize grown in the media valley of the Yaracuy river, Yaracuy state. To evaluated these methods, some experiments were carried out in the Experimental Station of Yaritagua (INIA), located in the Rodeo area, in Yaracuy state of Venezuela, firstly (1er year of the study) a N availability gradient was created by application of 0, 150, 300 and 450 kg N ha-1 like Urea, in a completed randomize block desing with 4 replications, and the crop response to 0, 45, 90, 120, 160, and 240 kg N ha-1 in the 2nd year of the estudy, in a split plot desing with 3 replications. The regresión, ANOVA, mean comparations, were carried out by SAS. The critical concentration of mineral N at the sowing time was 45.8, 31.3 and 28.0 mg kg-1 for the 0-10, 0-20 and 0-40 cm soil layers, while these were from 69.3 to 60.8 mg kg-1 for the layers 0-10 y 0-20 cm at the V5-V6 crop stage. The significan relationship found between soil mineral N and maximum yield let us to propose ranks of N availability to estimate N dosis for N availability measured at differents soil layers. About the use of the clorophilometer to evaluate the status of N in the crop, and to estimate N dose, we found that the SPAD lectures and the N concentration in leaf are sensitive to the dose of N applied in different crop stages. In addition, the SPAD lectures and N concentration are correlated with the yield of the crop in the different crop stages. The results shown that the clorophilometer could be used to detect N deficits at the field scale at the V5-V6 and V10-V11 crop stages. Moreover, it was possible to determine SPAD critical lectures and ranks them associated to crop response to N application, so we propose a procedure to determine N dose in accordance to the crop stage. In addition to this, we propose an index to estimate N dose for sidedressing using the mineral N concentration and the SPAD lecture at the V5-V6 stage. The NuMaSS program is an easy to handly system, and it was able to estimate N dose close to the observed ones, which decresed while the soil N availability increased due to the N dose applied in the first year. The estimation of soil N availability by using the N extracted by the crop without fertilizer was the best option to estimate the N dose, while the estimation of the soil N availability based in the mineralization of the soil organic matter overestimated the N dose. Moreover, the N dose estimated by NuMaSS show to be sensitive to to the amount of dry matter and N concentration in dry mater and grain, and to the efficiency of utilization of the N applied like fertilizer. About the INIA model, it was posible to calibrate the model to the Yaritagua area, by fitting of the Imax and Km parameters which are associated to the absortion of N from the soil, the Clim parameter which is the mimimum mineral N concentration below which the N are not absorbed by the crop from the soil, and the gAgua/gMS parameter which is a conversion parameter associated to the amount of water required to produce a unit of dry matter. The N dose estimate by the model INIA are in the same magnitude and in some cases statistically similar than the observed ones. Moreover, the N dose simulated by the INIA model decreases like the mineral N increse, that is similar that was observed in the field where the optimal N dose decrease when the mineral N increase. |
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