Mombaça grass yield as a function of nitrogen fertilization based on the use of the chlorophyll meter

The objective of this study was to evaluate the yield and agronomic efficiency of mombaça grass achieved with the management of nitrogen fertilization, based on the nitrogen sufficiency index (NSI) calculated using measurements obtained with a chlorophyll meter. The experiment was conducted in the field, in São Luís de Montes Belos - GO, Brazil, from November 2016 to May 2018, as a randomized-block design with six treatments and five replicates. Treatments consisted of six N fertilization management strategies (M), namely, M1 - reference, with 150 kg ha-1 N per application; M2 - recommended, with 50 kg ha-1 N per application; M3 - 50 kg ha-1 N when NSI < 98%; M4 - 50 kg ha-1 N when NSI < 94%; M5 - 50 kg ha-1 N when NSI < 90%; and M6 - control treatment, without N application. The NSI was monitored based on the relative chlorophyll content obtained with the chlorophyll meter. Forage canopy height, tiller density, and yield were evaluated. At the end of the 2nd cycle, the recommended, reference, NSI98%, NSI94%, and NSI90% treatments had received 1,050, 350, 300, 250, and 0 kg N ha-1. Control treatment obtained the lowest dry biomass yield, whereas the recommended, NSI98%, and NSI94% treatments showed the highest. Thus, N doses between 1,950 and 300 kg ha-1, in the second cycle, provided statistically equivalent yields in mombaça grass. Considering the DM of both evaluation cycles, the highest yield was achieved with the NSI98% and NSI94% treatments. The application of N doses of 250 to 1050 kg ha-1 provided similar yields. Therefore, the adoption of a nitrogen sufficiency index below 98% and 94% as a parameter allows a reduction and rational use of nitrogen fertilizer.

Effect of Different N Management on Improving N Efficiency in Rice- tarom Variety

The chlorophyll meter (SPAD) and leaf colour chart (LCC) are simple, portable diagnostic tools that can measure the crop N status in situ in rice fields to determine the timing of N top dressingAn experiment was carried out in Rice Research Institute in Mazandaran, in 2019. A test material has been evaluated in a Randomized Complete Block Design with three replications. Tarom variety were grown under eight treatments at plant density of 25*25 cm. Eight treatments included a zero-N control, o splits, chlorophyll meter 35, 37, 40, LCC 4 and 5. Result showed that Both LCC and SPAD can be used to improve N management for rice. The optimal SPAD threshold for determining the timing of N-application was 35. LCC treatments indicated that N-management based on LCC shade 4 helped avoid over application of N. Critical value of LCC 4 was more beneficial in enhancing the growth and agronomic, physiologic and internal efficiency. It is suggested that when N-management technology such as real time N-management (SPAD and LCC) were used, would avoid to over application of N fertilizer by rice farmers. The objective of this study is to determine critical threshold SPAD and LCC value of Tarom variety of rice(Oyiza Sativa L).

Wheat Grain Protein Content under Mediterranean Conditions Measured with Chlorophyll Meter

Adequate N fertilisation is crucial to increase the grain protein content (GPC) values in wheat. The recommended level of GPC needed to achieve high-quality bread-making flour should be higher than 12.5%. However, it is difficult to ensure the GPC values that the crop will achieve because N in grain is derived from two different sources: N remobilized into the grain from N accumulated in the pre-anthesis period, and N absorbed from the soil in the post-anthesis period. This study aimed to (i) evaluate the effect of the application of N on the rate of stem elongation (GS30) when farmyard manures are applied as initial fertilisers on GPC and on the chlorophyll meter (CM) values at mid-anthesis (GS65), (ii) establish a relationship between the CM values at GS65 and GPC, and (iii) determine a minimum CM value at GS65 to obtain GPC values above 12.5%. Three field trials were performed in three consecutive growing seasons, and different N fertilisation doses were applied. Readings using the CM Yara N-TesterTM were taken at GS65. The type of initial fertiliser did not affect the GPC and CM values. Generally, the greater the N application at GS30 is, the higher the GPC and CM values are. CM values can help to estimate GPC values only when yields are below 8000 kg ha−1. Additionally, CM values at GS65 should be higher than 700 to achieve high-quality bread-making flour (12.5%) at such yield levels. These results will allow farmers and cooperatives to make better decisions regarding late-nitrogen fertilisation and wheat sales.

Fertilization factor associated with nitrogen sufficiency index for nitrogen topdressing fertilization in common bean

ABSTRACT The current recommendations for nitrogen (N) doses may not contemplate the complex dynamics of N in the soil, what may imply in insufficiency to the crop demand. This study aimed to evaluate the use of two portable chlorophyll meters (Minolta SPAD 502 and ClorofiLOG model CFL 1030), after defining the nitrogen sufficiency index (NSI), to estimate the nitrogen fertilization factor in modern bean genotypes. A block design was used, with four replications. Each experiment consisted of four treatments, with doses of 0, 5, 10 and 20 kg ha-1 of N for each 1 % considered below the NSI defined as adequate for each cultivar. At the end of the cycle, the production components and yield were evaluated. It was not possible to obtain precise adjustments in the methodology for the TAA Gol cultivar. The fertilization factor of 12.5 kg ha-1 of N for each 1 % below the NSI of 90 % proved to be efficient for the Pérola cultivar, when the SPAD-502 chlorophyll meter was used. In genotypes with size and cycle characteristics similar to those of the BRSMG Uai cultivar and the VR 20 strain, using a fertilization factor between 14 and 16 kg ha-1 of N, the NSI of 95 % must be reduced, in order to increase the efficiency of the nitrogen fertilization.

Use of nitrogen sufficiency index to estimate topdressing doses for common bean

ABSTRACT Portable chlorophyll meters can be used to improve the prediction of nitrogen (N) doses for common bean. This study aimed to evaluate two chlorophyll meters (Minolta SPAD-502 and ClorofiLOG CFL 1030) to predict topdressing N doses for the Pérola, TAA Gol and BRSMG Uai cultivars and for the VR 20 line. Eight field experiments (four genotypes and two devices) were carried out in a randomized blocks design, with four replicates, being the treatments topdressing N applications corresponding to four nitrogen sufficiency indices. There were discrepancies between the indices obtained by the different devices for the same genotype, as well as among those obtained with the same device for the different genotypes studied. Thus, when the index is used to define the N doses, the genotype and the chlorophyll meter used must be considered. In addition, the recommended index of 95 % should not be generalized to all the cultivars and should be reduced.