Agriculture is facing challenges to produce more food in a climate scenario that works in the opposite direction. To amend this, agriculture has to invent new ways of making more with less. Interest in using by-products and finding new ways to utilize them has been increasing in recent years. The use of protein-rich sources for protein hydrolyzation and the use of these protein hydrolysates as biostimulants in plant production have been increasing. These mixtures are mainly produced by chemical and enzymatic hydrolysis from agro-industrial protein-rich by-products of animal, plant, and algal origins. The application of PHs has the potential to alleviate environmental stress; improve plant growth; and increase productivity, fruit yield, and abiotic-stress tolerance in agricultural crops. The use of these biostimulants offers a way to reduce the use of agrochemicals and agrees with the “do more with less” task in the future of agricultural production. This review gives an insight into the production of PHs, referring to sources of raw materials and methods of hydrolysis, the uptake and translocation of PHs, their effect on plant growth, the development and physiology, their role in alleviating stressful conditions, and their use in agriculture. The beneficial effects of PHs on different aspects of plant physiology, metabolism, and plant functioning under stressful conditions are evident. Inconveniently, crops, and sometimes even cultivars, are affected differently based on the way that PH is applied, the timing, and the concentration applied. Further research is needed to elucidate the mechanisms by which the components of PHs modify plant physiology and metabolism.

Apple is one of the most important economic fruit crops in the world. Despite all the strategies of integrated pest management (IPM), insecticides are still frequently used in its cultivation. In addition, pest phenology is extremely influenced by changing climatic conditions. The frequent spread of invasive species, unexpected pest outbreaks, and the development of additional generations are some of the problems posed by climate change. The adopted strategies of IPM therefore need to be changed as do the current monitoring techniques, which are increasingly unreliable and outdated. The need for more sophisticated, accurate, and efficient monitoring techniques is leading to increasing development of automated pest monitoring systems. In this paper, we summarize the automatic methods (image analysis systems, smart traps, sensors, decision support systems, etc.) used to monitor the major pest in apple production (Cydia pomonella L.) and other important apple pests (Leucoptera maifoliella Costa, Grapholita molesta Busck, Halyomorpha halys Stål, and fruit flies—Tephritidae and Drosophilidae) to improve sustainable pest management under frequently changing climatic conditions.

Fluctuating asymmetry (FA) is used in assessing the effect of environmental stress on the development stability of individuals by measuring small random deviations from perfect bilateral symmetry. Here, we checked for FA on two predatory carabid beetles, Pterostichus melas and Poecilus koyi, in order to evaluate species response to agricultural practices within Mediterranean agroecosystems, as well as FA as a method. The samples were collected in vineyards and olive groves, both under integrated pest management (IPM) and ecological pest management (EPM), and in pristine habitats in the Mediterranean region of Croatia. Geometric morphometrics (GMMs) were used to analyze the pronotum and abdomen shape variations and left–right asymmetries of each population. In respect to the FA measurements, analyzed species responded differently, with P. koyi displaying a lower intensity of FA than P. melas. On the other hand, P. melas beetles from vineyards showed a higher intensity of FA compared with populations from pristine habitats and olive groves. Accordingly, FA pointed out olive groves as potentially less adverse habitats to predatory carabids, keeping in mind the different levels of asymmetry between the two species. Our study singled out P.melas as a more suitable species for further research, in the effect that different agricultural practices can have their impact on non-target invertebrates analyzed by measuring the FA.

For the first time the effects of different sampling periods and their interaction with five major autochthonous Croatian Istrian olive cultivars and the Italian cultivar ‘Leccino’ on the quantity and composition of olive leaf phenolic compounds and mineral nutrients were investigated. For that purpose, olive leaves were sampled in two collecting periods, in October and March, coinciding with the harvesting and pruning periods, respectively. All selected cultivars had a higher oleuropein leaf content in the pruning collecting period, with the highest levels noted for the ‘Leccino’ and ‘Buža’ cultivars. Cultivar significantly affected almost all the investigated phenols, with higher concentrations of these valuable compounds in the pruning than in the harvesting period. Differences observed in leaf mineral composition were closely related to the differences in phenolic profiles and were significantly affected by genotype. Some of the studied mineral nutrients, such as P, Cu and B, were found to be significantly correlated with the most abundant olive leaf phenolic compounds, oleuropein and verbascoside.

In this review, an overview was given of the mutual interactions between nematodes and fungi of the genus Trichoderma sp. due to the potential of these fungi to protect plant roots from plant-parasitic nematodes on the one hand and the influence of nematodes (fungivores) on the efficacy of the fungus on the other. In addition, an overview of the advantages of Trichoderma sp. for agricultural production was given. The basis of sustainable agricultural production is the healthy functioning of the soil ecosystem. The diversity of organisms—bacteria, protozoa, algae, metazoans (nematodes) and fungi—improves the quality and performance of the soil by maintaining biological productivity. Root exudates in the rhizosphere support microbial communities that play a key role in regulating the dynamics of organic matter decomposition and the availability of plant nutrients. The microbial activity of organisms in the soil is interconnected and interacts to form a soil food web that reflects the condition, function and health of the soil. The energy in food webs flows through trophic chains of consumers, which are divided into energy channels. Root, bacterial and fungal channels increase soil biomass, carbon (C) and energy flow through the soil food web. The structure of the nematode community is an effective tool for the biological assessment of soil quality. This is due to a number of characteristics that nematodes have, including the following: a great diversity of species, the possibility of subdivision according to different criteria such as trophic groups and c-p groups, the duration of reproduction, the ease of sampling, the identification of genera and preservation, etc. Nematodes are involved in various ecological functions in the soil, of which the interaction between them and fungi is based on antagonism or mutualism, which is the basis for a better understanding of their impact on the ecosystem. Fungi of the genus Trichoderma sp. are successful colonizers of all habitats, secondary opportunists and fast growing.

Croatian islands are olive growing areas characterized by poor conditions for olive trees because of karst soil and a precipitation deficiency. Under these conditions, irrigation is a very important factor for constant olive oil production. This paper aims to investigate the effects of different watering regimes on quantity, sensory and chemical quality and composition of Coratina cv. olive oil obtained from trees grown on ameliorate karst soil during two harvesting years. Olive trees were subjected to rainfed conditions and three different irrigation treatments (T₁—deficit irrigation representing the usual producer’s practice, T₂—regulated deficit irrigation in respect to phenological stages, T₃—full irrigation). Irrigation treatments increased oil yield compared to rainfed conditions (T₁ + 58%, T₂ + 66% and T₃ + 74%, representing average values for both studied years). All olive oil samples were of extra quality. Irrigation led to a decrease in carotenoids, volatiles, polyunsaturated fatty acids and linolenic acid contents, with no difference found among irrigation treatments. Total phenols and secoiridoids concentration was not affected by irrigation, indicating that similar oil quality could be achieved with less demand on the water supply. Obtained results could help producers to define a suitable irrigation management in particular conditions of ameliorate karst.