Francesco Tei

Nitrogen Concentration Estimation in Tomato Leaves by VIS-NIR Non-Destructive Spectroscopy

Nitrogen concentration in plants is normally determined by expensive and time consuming chemical analyses. As an alternative, chlorophyll meter readings and N-NO3 concentration determination in petiole sap were proposed, but these assays are not always satisfactory. Spectral reflectance values of tomato leaves obtained by visible-near infrared spectrophotometry are reported to be a powerful tool for the diagnosis of plant nutritional status. The aim of the study was to evaluate the possibility and the accuracy of the estimation of tomato leaf nitrogen concentration performed through a rapid, portable and non-destructive system, in comparison with chemical standard analyses, chlorophyll meter readings and N-NO3 concentration in petiole sap. Mean reflectance leaf values were compared to each reference chemical value by partial least squares chemometric multivariate methods. The correlation between predicted values from spectral reflectance analysis and the observed chemical values showed in the independent test highly significant correlation coefficient (r = 0.94). The utilization of the proposed system, increasing efficiency, allows better knowledge of nutritional status of tomato plants, with more detailed and sharp information and on wider areas. More detailed information both in space and time is an essential tool to increase and stabilize crop quality levels and to optimize the nutrient use efficiency.

Decreasing Nitrate Leaching in Vegetable Crops with Better N Management

The relatively low cost of fertiliser and the increasing demand and competition for cheap food have encouraged the over-fertilisation of field vegetables over the past few decades. However, more recent scientific and public concern over eutrophication of water and the accumulation of nitrates in vegetables for human consumption requires a more effective use of nitrogen fertilisers in a more sustainable manner, which minimises the potential risk of negative effects on the environment and human health. In this review, we present the current state of the art in knowledge of N dynamic in vegetable crops and the latest advances in nutrient management, which could be used to mitigate nitrate losses from vegetables fields to the wider environment. Findings are based on published data and personal communications with researchers and consultants across Europe. Areas of research where further work is required are identified and described. A conclusive chapter reports on the economic and environmental impact of technology transfer of improved nitrogen management in three south European states and in the Netherlands.

Actual N availability from winter catch crops used for green manuring in maize cultivation.

Field experiments were carried out in Central Italy on several green manure species (pure or mixed) and on succeeding grain maize to find practical relationships for predicting the N effect (N absorbed by maize that derives from the actual gain in soil available N due to green manure). Actually, little information is available for Mediterranean environments, where green manure species and strategies may be other than those of northern-temperate and tropical regions. Relationships were found for maize shooting (Neff = −3.61DW + 29.75N%; R2 = 0.67), flowering (Neff = −1.32DW + 27.47N%; R2 = 0.66) and physiological maturity (Neff = −4.84DW + 50.43N%; R2 = 0.74) (DW = incorporated biomass, N% = N concentration).

RELIABILITY OF PETIOLE SAP TEST FOR N NUTRITIONAL STATUS ASSESSING IN PROCESSING TOMATO

A field experiment was carried out in Central Italy to assess the reliability of petiole sap for determining nitrogen (N) status on processing tomato. The crop was fertilized with different N rates and fertigation-irrigation frequencies. Reduced-N and nitrate-N concentrations were determined by lab analyses at 30, 42, 57, 71, and 84 days after transplanting. At each sampling date, the assessment of N nutritional status as resulted by sap test was compared with the actual plant N status as determined by nitrogen nutrition index (NNI). Results from sap test were in agreement with NNI indications for about 2/3 of crop cycle that represents the crucial time for N fertilizer management in tomato. The correlation coefficient of the two methods was, on average 0.854 and it was statistical significant in the whole sampling period. The nitrate concentration in the petiole sap provided a good agreement with laboratory analysis across the full range on N-nitrate (NO3) concentrations examined.

Washing and/or Cutting Petioles Reduces Nitrate Nitrogen and Potassium Sap Concentrations in Vegetables

ABSTRACT Petiole sap testing using ion-specific electrodes is a simple method that can be used to guide in-season applications of nitrogen (N) and potassium (K) to vegetable crops. This method requires petiole sampling and sap extraction using a sap press. Because some vegetables are grown with foliar applications of N and/or K and because some crops have large petioles, petioles may need to be washed and/or cut before being pressed. Limited information is currently available on the effect of washing/cutting on sap-testing results. Hence, muskmelon (Cucumis melo L.), bell pepper (Capsicum annum L.) and tomato (Lycopersicon esculentum Mill) petioles were used to test whether washing/cutting reduced NO3 (nitrate)-N and K concentrations and changed the subsequent interpretation of plant nutritional status. Washing for 30, 60, or 120 sec in distilled water and cutting petioles before or after washing significantly reduced sap concentrations (p = 0.01 and p = 0.04 for NO3-N and K, respectively) in seven of 12 tests when compared with the control method (petioles cut and not washed). The average concentration reductions between the control and the lowest value among all the washing/cutting treatments were 30% for NO3-N and 19% for K. These losses due to washing/cutting are likely often to change the diagnosis of nutritional status from “sufficient” to “less than sufficient” and, therefore, may suggest the need for unnecessary fertilizer applications.

Depth and Width of the Wetted Zone in a Sandy Soil after Leaching Drip‐Irrigation Events and Implications for Nitrate‐Load Calculation

Abstract The quantitative assessment of nitrate‐nitrogen (NO3‐N) leaching below the root zone of vegetable crops grown with plasticulture (called load) may be done using 150‐cm‐deep soil samples divided into five 30‐cm‐long subsamples. The load is then calculated by multiplying the NO3‐N concentration in each subsample by the volume of soil (width×length×depth, W×L×D) wetted by the drip tape. Length (total L of mulched bed per unit surface) and D (length of the soil subsample) are well known, but W is not. To determine W at different depths, two dye tests were conducted on a 7‐m‐deep Lakeland fine sand using standard 71‐cm‐wide plasticulture beds. Dye tests consisted of irrigation lengths of up to 38 and 60 h, digging transverse sections of the raised beds at set times, and taking measurements of D and W in 30‐cm‐deep increments. Most dye patterns were elliptically elongated. Maximum average depths were similar (118 and 119 cm) for both tests despite differences in irrigation duration and physical proximity of both tests (100 m apart in the same field). Overall, D response (cm, both tests combined) to irrigation volume (V, L/100 m) was quadratic (Dcomb.avg=−2×10−7 V2+0.008 V+34), and W responses (using maximum and mean values at each 30‐cm increment depth, Wmax and Wmean, respectively) to D (cm) were linear (Wmax=−0.65D+114 and Wmean=−0.42D+79). Predicted Wmax were 104, 84, 64, 44, and 25 cm in 30‐cm depth increments. Load calculations using NO3‐N concentrations of 7.2, 5.0, 3.9, 3.0, and 2.9 µg/kg for the 15, 46, 77, 107, and 137 cm depths, respectively, were 21.2, 37.6, 28.2, and 39.1 kg/ha for W values of 40 cm, bed width (71 cm), Wmean, and Wmax, respectively. These load calculations ranged from simple to double based on the choice of W estimate used, which illustrates the importance of knowing W accurately when load is calculated from field measurements. These Wmax and Wmean values may be used for load calculations on sandy soils but are likely to overestimate load because they were determined without transpiring plants and may need to be adjusted for different soil types.

Use of two grasses for the phytoremediation of aqueous solutions polluted with terbuthylazine

ABSTRACT The capacity of two grasses, tall fescue (Festuca arundinacea) and orchardgrass (Dactylis glomerata), to remove terbuthylazine (TBA) from polluted solutions has been assessed in hydroponic cultures. Different TBA concentrations (0.06, 0.31, 0.62, and 1.24 mg/L) were chosen to test the capacity of the two grasses to resist the chemical. Aerial biomass, effective concentrations (to cause reductions of 10, 50, and 90% of plant aerial biomass) and chlorophylls contents of orchardgrass were found to be more affected. Tall fescue was found to be more capable of removing the TBA from the growth media. Furthermore, enzymes involved both in the herbicide detoxification and in the response to herbicide-induced oxidative stress were investigated. Glutathione S-transferase (GST, EC. 2.5.1.18) and ascorbate peroxidase (APX, EC. 1.11.1.11) of tall fescue were found to be unaffected by the chemical. GST and APX levels of orchardgrass were decreased by the treatment. These negative modulations exerted by the TBA on the enzyme of orchardgrass explained its lower capacity to cope with the negative effects of the TBA.

Crop Rotation as a System Approach for Soil Fertility Management in Vegetables

This paper reviews the recent literature on crop rotation as a tool to manage soil fertility specifically for vegetable production. All of the aspects dealing with soil fertility management, i.e. mineral and organic fertilisation, crop residue s management, cover cropping and green manuring, and intercrop ping, are examined in the frame of crop rotations in conventional and organic systems for both specialised and non-specialised vegetable production. A focus is given on conservation tillage practices to manage green manures and vegetable crop residues. The design and modelling of vegetable rotations are described under the viewpoint of increasing the nutrient use efficiency and the self-sufficiency of the system. Some long-term experiments including vegetables are described which evaluate cumulated effects of rotations on soil fertility and vegetable production. It is concluded that only integrating all the available techniques of soil fertility management at a whole rotation scale it is possible to contribute to the productive, economic and environmental sustainability of the system. For example, little supplementation of mineral or fast-release organic fertilisers delivered with rational fertilisation techniques (e.g. starter, split, and localised fertilisation; fertigation) may help compensate the temporal and spatial lack of matching between nitrogen release from slow-release organic sources and crop nitrogen demand. This would help modulate nutrient supply in a more flexible way and improve crop nutrient uptake, so allowing more constant yields across years and limited risks of nutrient loss to the environment.

RELIABILITY OF NDVI DERIVED BY HIGH RESOLUTION SATELLITE AND UAV COMPARED TO IN-FIELD METHODS FOR THE EVALUATION OF EARLY CROP N STATUS AND GRAIN YIELD IN WHEAT

This study was aimed at comparing in-field parameters and remote sensing NDVI (normalized difference vegetation index) by both satellite (SAT) and unmanned aerial vehicle (UAV) for the assessment of early nitrogen (N) status and prediction of yield in winter wheat (Triticum aestivum L.). Six increasing N rates, i.e., 0, 40, 80, 120, 160, 200 kg N ha−1 were applied, half at tillering and half at shooting. Thus, when the crop N status was monitored between the two N applications, consecutive N treatments differentiated from each other by just 20 kg N ha−1. The following in-field and remote sensed parameters were compared as indicators of crop vegetative and N status: plant N% (w:w) concentration; crop N uptake (Nupt); ratio between transmitted and incident photosynthetically active radiation (PARt/PARi); leaf SPAD values, an indirect index for chlorophyll content; SAT and UAV derived NDVI. As reliable indicators of wheat N availability, in-field parameters were ranked as follows: PARt/PARi ≅ Nupt > SPAD ≅ N%. The PARt/PARi, Nupt and SPAD resulted quite strongly correlated to each other. At all crop stages, the NDVI was strongly correlated with PARt/PARi and Nupt. It is of relevance that NDVI correlated quite strongly to in-field parameters and grain yield at shooting, i.e., before the second N application, when the N rate can still be adjusted. The SAT and UAV NDVIs were strongly correlated to each other, which means they can be used alternatively depending on the context.

The Role of Research for a Sustainable Fertilization Management in Vegetables: Future Trends and Goals

Global vegetable production amounts to 1.13 billion tonnes from about 58 million of hectares; in the last decade global vegetable production increased at an average annual rate of around 3% although significant variability can be found in function of the region and the country. Beyond their monetary value, vegetables are important dietary sources of micronutrients so sustainable fertilization management should be aimed to produce healthy and environmentally sustainable vegetables by taking into considerations peculiarities of the vegetable production. Vegetables represent about 9% of the world market in fertilizer consumption (i.e. about 16 Mt, of which 9.1% of N, 9.4 of P2O5 and 10.0% of K2O). In the twenty-first century the research would be aimed at producing economical yields with reduced fertilizer inputs by the development and implementation of cropping systems, nutrient management approaches and crop varieties both showing higher nutrient/fertilizer use efficiency.