Theoretical Determination of a Critical Nitrogen Dilution Curve Based on the Carrot Case Study
The objectives of the present study were to: (a) formulate a general dilution equation for a critical nitrogen percentage in a leaf (Nc); (b) monitor dilution function of carrot as a case study; (c) demonstrate applicability of digital color imaging to monitor total nitrogen (Ntot) in crops. Carrot (Daucus carota) was grown on loess soil at five Ntot application rates. Ntot weight (kg/ha) was obtained by standard laboratory analysis and by image processing. Total yield of the treatments was the sum of canopy and roots dry matter. A new logistic decay curve Nc = a/[1 + (W/W0)b] agreed with experimental data. Nc (g/kg) is the critical nitrogen level, a and b are coefficients, and W/W0 is the relative dry matter biomass. Values of Nitrogen Nutrition Index (NNI) ≥ 1.0 indicated that there was no nitrogen deficiency in treatment larger than 100% application of Ntot. The weight of nitrogen in form of multiplication of the dry leaves weight (W) and N percent is suitable for the determination of nitrogen status. The availability of image-based data for N percent is faster, timely and less expensive than that of laboratory test. Applicability of digital color camera to monitor Ntot in crops instead of laboratory test was successfully demonstrated.
Proximal Sensing of Nitrogen Needs by Spring Wheat
Canopy nitrogen (N) status relates strongly to canopy chlorophyll content and the strength of green color. Proximal photograph by RGB camera was used to select green features that has the potential to assess N content at leaf of plant as a function of its the greenness. We proposed the development of it as a tool for sensing nitrogen content in spring wheat (Triticum aestivum). Image processing algorithm was programed calibrated and validated wheat %N%N. Nitrogen uptake =%N × canopy dry matter was harvested and calculated using simulated dry matter by DSSAT model. The data replicated laboratory measurements. A linear Lab vs Camera model displayed a unit slope with r2 = 0.93. Increase of dry matter was successfully surrogated by days after emergence and used as abscissa for inverse logistic model of critical nitrogen level. It decreased gradually from about 6% to 2% as days after emergence increased from 0 to 110 days. Maximum N uptake calculated from photo and laboratory was 324 Kg ha−1 and 318 Kg ha−1 respectively suggesting insignificant difference. Physiological N-use efficiency (i.e., canopy weight/N weight) was 52 and 78 kg canopy dry weight per 1 kg N for early and late-ripening cultivars, respectively. The determination of N application based on the smartphone photograph proved to be useful by saving on time and expenses for growers who have access to smartphones and can use them for N application and management.
Impact of long and short term irrigation of a sodic soil with distillery effluent in combination with bioamendments.
The study reports the effects of irrigation of a sodic soil with post methanation effluent (PME) of a distillery. Impact of long term effluent irrigation in the field (10 years) and short term effluent irrigation using different doses of PME in the laboratory (30 days) was studied in combination with three bioamendments i.e. farmyard manure, brassica residues and rice husk. Impact on various soil properties like EC, pH, total organic carbon (TOC), total Kjeldahl nitrogen (TKN), available phosphorus, exchangeable K, Na, Ca, Cl, microbial population and soil enzyme activities were studied. Long term application of PME proved useful in significantly increasing TOC, TKN, K, P and soil enzymatic activities in the soil but tended to build up harmful concentration of Na, that could be chelated by bioamendments. In short terms studies, application of 50% PME along with bioamendments proved to be the most useful in improving the properties of sodic soil and also favoured successful germination and improved seedling growth of pearl millet.