Fertilization is an important management strategy of yams (Dioscoreaspp.) especially when grown in degraded soils. A field study evaluated the leaf numbers, leaf area indices, crop growth, yields, and nitrogen (N) and potassium (K) use efficiencies ofD. alataandD. rotundatain Côte d'Ivoire when grown in two contrasting soils with and without fertilizer.D. alatahad a lower number of leaves per vine, although leaf area indices were higher, and the leaves were retained for a longer period than inD. rotundata. In all situations, the yields ofD. alatawere significantly higher, and fertilizers promoted growth of shoots, roots, tubers, and, thus, final yields especially in the low fertile savanna soil. The beneficial impact of fertilizer on yields was significantly lower in the fertile forest soils. The nutrient use agronomic efficiencies indicated the impact of both N and K in promoting yields especially under nonfertilized conditions.
Soil fertility decline and high N demand during plant growth are cited as main causes of low yield in yam (Dioscorea spp.). As information regarding fertilizer N use in yam is lacking, a field experiment was undertaken in 2006 and repeated in 2007 in central Côte d'Ivoire using 15N (15NH415NO3) labeled fertilizers to monitor N uptake and fertilizer use efficiency in D. alata. The 15N‐labeled fertilizer was added in two splits (at 90 and 130 d after planting) for a target tuber yield of 40 Mg fresh tuber ha−1. The application of mineral fertilizers increased total biomass production and tuber yield as well as N uptake from native soil organic matter. The recovery of 15N‐labeled fertilizer applied at 90 and 130 d after planting was not significantly different but the year affected 15N recovery by the plant. The maximum 15N recoveries calculated from the sum of the 15N recovery measured at both application dates were 46 and 23% in 2006 and 2007, respectively. Leaf dry matter and leaf N uptake were higher in 2006 than in 2007, but tuber dry matter was not different between years at the final harvest. Up to 170 kg N ha−1 was returned to the soil through the fallen shoots, indicating an important recycling of N for soil fertility replenishment. Thus, crop succession or intercropping are encouraged in a yam cropping system. Our results also show that the application of mineral fertilizers had a strong “priming effect” on the native soil N in both years.
Ce travail a pu être réalisé grâce à l'aide financière octroyé par la Société NSIA-VIE Assurances Côte d'Ivoire. RESUME Une étude a été conduite pour mettre au point des composts riches en fertilisants à partir des déchets de ferme, par une méthode de compostage rapide. A partir des fientes de poulets de chair, de pondeuses et de déjections de boeuf, neuf types de composts regroupés respectivement en trois catégories A, B et C ont été obtenus. Ces composts, basés sur la combinaison de fumier et de fibre de coco sont composés selon les rapports 1/1 ; 1/2 et 2/1. Pendant 74 jours de compostage, les tas sont fréquemment retournés et les températures internes relevées. Les composts de déchets de volailles ont présenté des températures maximales supérieures à 69 °C, et celles des déjections de boeufs inférieures à 55 °C. Le rapport C/N des composts a varié de 10 à 12 pour les rapports 1/1 et 1/2, et a été inférieur à 10 pour le rapport 2/1. Le pH des composts finaux a varié de 7,45 à 8,13. Les minéraux N, P, K, dosés ont donné les plus fortes valeurs pour le type B2 :1, respectivement 34,7 ; 24,0 et 29,8 g/kg MS. Ces composts riches en éléments minéraux pourraient être utilisés en agriculture biologique et surtout en culture hors-sol.
In-field proximal sensing of most major crops nutrients still remains an economical and technical challenge. For this purpose, the use of effective multi-excitation fluorescence and reflectance wavelengths is explored in this work on Okra plant. Visible-near infrared (400 -1000 nm) reflectance and multi-fluorescence data were collected at leaf scale in a chemically fertilized field by using an USB spectrometer mounted with an Arduino-based LED driver clip. N, P, K and Ca content of samples leaves were measured using reference methods. Average pods yield and leaves macronutrients content were calibrated using IRIV-PLS regression after spectra pretreatments. Single informative wavelengths bands in reflectance, red and far-red fluorescences were selected for building yield and macronutrient content models. We showed that flowering stage was more suitable for yield prediction. Moderately useful macronutrient models were found in Ca content (RPD val = 1.93, r P = 0.818) and potassium content with RPD val = 1.8, r P = 0.88. P and N yielding prediction performance of RPD val = 1.61 (r P = 0.718 ) and RPD val = 1.46 (r P = 0.56) respectively were less accurate. This study demonstrates potentiality of fluorescence and reflectance spectroscopy for accurate estimation of leaf macronutrient content and crop yield. High selectivity obtained from resulted spectral bands could lead to the development of reliable, rapid and cost-effective devices for nutrient diagnosis.
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