Monitoring Sunflower and Maize Canopy Under Alternative Nitrogen Regimes with Lidar and Optical Sensors

Crop fertilization is an important part of cost and energy inputs in agriculture. The opportunity to apply the variable rate of nitrogen fertilizers according to the plant needs in each part of the field is a promising practice to increase the fertilizer use efficiency. An experiment was conducted in 2016 in the University of Thessaly farm, Central Greece in order to evaluate the use of lidar and optical sensors to monitor the crop canopy for sunflower and maize. The canopy development can serve as a good indicator for the nutrition state of the crops regarding especially the nitrogen, and it can be used as an indicator for variable rate application systems. In order to obtain plants with different canopy development, a field experiment was established with treatments receiving the normal, farmer's practice, nitrogen rates (100%N) at basic fertilization, treatments receiving 50% reduced nitrogen fertilizer (50%N) and treatments with no nitrogen application (0%N). During growing, the crop canopy was monitored with a lidar and an optical sensor. Manual measurements of plant height and weight were also made. The manual measurements revealed the effect of variable fertilizer rates to plant development. The plots with higher nitrogen rates had higher and more vigor plants. The lidar sensor depicted more clearly these differences compared to the optical sensor. Plant height was sufficiently assessed for both the sunflower and maize crop by lidar. Plant volume though was assessed only for the sunflower. A problem with the lidar sensor was the small sampling rate (almost 2Hz) but this can be compensated by its ability to scan simultaneously more than one crop rows (4 to 6) and obtain multiple sample information

Nitrogen replenishment using variable rate application technique in a small hand-harvested pear orchard

Precision agriculture is a management approach for sustainable agriculture. It can be applied even in small fields. It aims to optimize inputs, improve profits, and reduce adverse environmental impacts. In this study, a series of measurements were conducted over three growing seasons to assess variability in a 0.55 ha pear orchard located in central Greece. Soil ECa was measured using EM38 sensor, while soil samples were taken from a grid 17 × 8 m and analysed for texture, pH, P, K, Mg, CaCO3, and organic matter content. Data analysis indicated that most of the nutrients were at sufficient levels. Soil and yield maps showed considerable variability while fruit quality presented small variations across the orchard. Yield fluctuations were observed, possibly due to climatic conditions. Prescription maps were developed for nitrogen variable rate application (VRA) for two years based on the replacement of the nutrients removed by the crop. VRA application resulted in 56% and 50% reduction of N fertiliser compared to uniform application

Seed Germination and Seedling Emergence of Shepherd's needle (Scandix pecten-veneris) as Affected by Seed Weight or Burial Depth

Shepherd's needle (Scandix pecten-veneris L.) is a very common broadleaf weed of winter cereals and also an edible weed used in many regions in Greece. Knowing the behavior of the weed seeds in the soil may help in designing its management strategy and its future cultivation. Field and laboratory experiments were conducted to evaluate the effect of seed weight or burial depth on seed germination and seedling emergence in 2008 and 2010. For seed weight effect on germination and seedling emergence light and heavy seeds were tested by Petri dish assay and in the field (sowing depth 4 cm). For burial depth study six depths - 2.5, 5, 7.5, 10, 12.5 and 15 cm - were examined in field trials made in two periods of time: 25 November and 15 March for two years. Percentage of seed germination, seedling emergence and mean emergence time were measured. Results showed that light seeds germinated better (74±2.2-95±2.2%) and earlier (20.5±0.64-31.0±0.45 days) than heavy seeds (34±3.2-58±5.1% and 25.4±0.57-33.8±0.46 days, respectively). The burial depth influenced seedling emergence and mean emergence time (MET) in most cases. Low emergence percentage (1.7±1.1-33.8±7.2%) was found at the depth of 15 cm and high at depth of 2.5, 5, 7.5 cm. Seeds sowed 15.0 cm deep had higher MET (27.0±0.9-55.1±1.1 days) than those sowed at 2.5 cm (20.9±0.9-41.6±0.5 days)

Development of an Energy Efficient and Fully Autonomous Low-Cost IoT System for Irrigation Scheduling in Water-Scarce Areas Using Different Water Sources

Politicians and the general public are concerned about climate change, water scarcity, and the constant reduction in agricultural land. Water reserves are scarce in many regions in the world, negatively affecting agricultural productivity, which makes it a necessity to introduce sustainable water resource management. Nowadays, there is a number of commercial IoT systems for irrigation scheduling, helping farmers to manage and save water. However, these systems focus on using the available fresh water sources, without being able to manage alternative water sources. In this study, an Arduino-based low-cost IoT system for automated irrigation scheduling is developed and implemented, which can provide measurements of water parameters with high precision using low-cost sensors. The system used weather station data combined with the FAO56 model for computing the water requirements for various crops, and it was capable of handling and monitoring different water streams by supervising their quality and quantity. The developed IoT system was tested in several field trials, to evaluate its capabilities and functionalities, including the sensors’ accuracy, its autonomous controlling and operation, and its power consumption. The results of this study show that the system worked efficiently on the management and monitoring of different types of water sources (rainwater, groundwater, seawater, and wastewater) and on automating the irrigation scheduling. In addition, it was proved that the system is can be used for long periods of time without any power source, making it ideal for using it on annual crops

Life Cycle Assessment of Variable Rate Fertilizer Application in a Pear Orchard

Precision Agriculture (PA) is a crop site-specific management system that aims for sustainability, adopting agricultural practices more friendly to the environment, like the variable rate application (VRA) technique. Many studies have dealt with the effectiveness of VRA to reduce nitrogen (N) fertilizer, while achieving increased profit and productivity. However, only limited attention was given to VRA’s environmental impact. In this study an International Organization for Standardization (ISO) based Life Cycle Assessment (LCA) performed to identify the environmental effects of N VRA on a small pear orchard, compared to the conventional uniform application. A Cradle to Gate system with a functional unit (FU) of 1 kg of pears was analyzed including high quality primary data of two productive years, including also the non-productive years, as well as all the emissions during pear growing and the supply chains of all inputs, projecting them to the lifespan of the orchard. A methodology was adopted, modelling individual years and averaging over the orchard’s lifetime. Results showed that Climate change, Water scarcity, Fossil fuels and Particulate formation were the most contributing impact categories to the overall environmental impact of the pear orchard lifespan, where climate change and particulates were largely determined by CO2, N2O, and NH3 emissions to the air from fertilizer production and application, and as CO2 from tractor use. Concerning fertilization practice, when VRA was combined with a high yield year, this resulted in significantly reduced environmental impact. LCA evaluating an alternative fertilizer management system in a Greek pear orchard revealed the environmental impact reduction potential of that system

Effects of Row Spacing on Growth, Yield and Quality Parameters of Sweet Sorghum

A two-year field experiment was conducted in Thessaly, Central Greece, in order to evaluate the effect of row spacing on several growth and yield parameters of sweet sorghum. In particular, two row spacings were tested: wide row spacing (WRS) at 0.75m and narrow row spacing (NRS) at 0.375m. During the growing period, crop growth in terms of plants' emergence, plants' height, panicle appearance, while stalk sugar content, dry biomass and total sugar yield were also evaluated. In addition, plant material was analysed to assess the potential effects of the treatments on stalk quality. The results showed that with the appropriate cultural practices, sweet sorghum can yield over 40 Mg ha-1 of dry matter and over 18 Mg ha-1 of total sugar yield under Greek conditions. Narrow row spacing resulted to higher plant population and productivity in terms of dry matter and total sugar yield (61% and 37% increase, respectively) in the first year, but without any statistical significant difference compared to the wide spacing in the second year. The compositional analysis of the crop samples revealed significant effects of row spacing on water soluble matter, cellulose and hemi-cellulose content revealing a beneficial effect of narrow row spacing on the quality and consequently ethanol production

Nitrogen replenishment using variable rate application technique in a small hand-harvested pear orchard

Precision agriculture is a management approach for sustainable agriculture. It can be applied even in small fields. It aims to optimize inputs, improve profits, and reduce adverse environmental impacts. In this study, a series of measurements were conducted over three growing seasons to assess variability in a 0.55 ha pear orchard located in central Greece. Soil ECa was measured using EM38 sensor, while soil samples were taken from a grid 17 x 8 m and analysed for texture, pH, P, K, Mg, CaCO3, and organic matter content. Data analysis indicated that most of the nutrients were at sufficient levels. Soil and yield maps showed considerable variability while fruit quality presented small variations across the orchard. Yield fluctuations were observed, possibly due to climatic conditions. Prescription maps were developed for nitrogen variable rate application (VRA) for two years based on the replacement of the nutrients removed by the crop. VRA application resulted in 56% and 50% reduction of N fertiliser compared to uniform application

Nitrogen replenishment using variable rate application technique in a small hand-harvested pear orchard

Precision agriculture is a management approach for sustainable agriculture. It can be applied even in small fields. It aims to optimize inputs, improve profits, and reduce adverse environmental impacts. In this study, a series of measurements were conducted over three growing seasons to assess variability in a 0.55 ha pear orchard located in central Greece. Soil ECa was measured using EM38 sensor, while soil samples were taken from a grid 17 × 8 m and analysed for texture, pH, P, K, Mg, CaCO3, and organic matter content. Data analysis indicated that most of the nutrients were at sufficient levels. Soil and yield maps showed considerable variability while fruit quality presented small variations across the orchard. Yield fluctuations were observed, possibly due to climatic conditions. Prescription maps were developed for nitrogen variable rate application (VRA) for two years based on the replacement of the nutrients removed by the crop. VRA application resulted in 56% and 50% reduction of N fertiliser compared to uniform application