This study evaluates the status of the internet of things (IoT) application in irrigation practices by focusing on the research direction, leading countries and productive researchers. The data from this study was extracted from the Scopus database and analysed using a Publish or Perish and a VOSviewer software for citation analysis and bibliometric map, respectively. The present study reveals that rapid increment of the articles in the subject area began in year 2016 and continues growing until today. India become the most productive country (n = 271), followed by China (n = 88), Indonesia (n = 41) and Malaysia (n = 32) in this topic. The most three prolific authors in this subject area are Wenyan Wu (Birmingham City University, UK), Steve Attard (AgriTech Solutions, Australia), and Yvette Everingham (James Cook University, Australia). This study gives insights into an overview of current and frontier research in the application of the IoT in irrigation related approach. It provides an idea to researcher to contribute the knowledge in under explored research domain.

The yield of the crops may be subject to the distribution of water directly to the plant root zone using drippers or emitters. To date, there has not been adequate work to evaluate irrigation system performance and water productivity (WP) specifically for rock melon inside a netted rain house shelter in tropical area. Amongst the problem of this system is the non-functional irrigation components after been used for specific of time, thus reducing the irrigation efficiencies and distribution uniformity. This study evaluates irrigation performance of drip irrigation system and estimates WP of rock melon cultivation in the netted rain house shelter. The results indicate that the operating pressure of the drip irrigation system tested varied from 0.8 to 3.0 psi with a discharge rate between 0.14 and 0.25 Lmin−1. Water application uniformity between laterals varied from 66.06 to 89.72%. The WP of rock melon was around 7.93 kg/m3, which is considerably high and in similar range as demonstrated in previous literature. The field evaluation also reveals that the manipulation of valve controller at lateral based on a few selected scenarios did not provide a significant difference in pressure and discharge at the head, middle, and tail section of the drip irrigation system. Such findings would be a very useful information for a precision water management particularly for rock melon cultivation grown under rain house shelter system.

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Abundance of marginal soils is among the major constraint to achieve high yield for crop production due to unsuitable physical and chemical properties of the soils. Commonly, farmers would manage the marginal soil by adding soil amendment, compost and fertilizer which increase the cost of production. Alternatively, application of fertilizer together with plant growth regulator (PGR) during crop management can be practiced to utilize the marginal soil effectively. The aim of this experiment was to determine effects of phosphorus (P) fertilizer and PGR namely ethephon on growth performance of sweet corn grown in three marginal soils namely Rasau, Kuah and Dampar. The treatments were arranged as factorial randomized complete block design with four rates of P fertilizer and standard rate of ethephon replicated four times. The results indicated that the physical properties of the marginal soils vary which Rasau dan Kuah series have low content of silt (10.30% and 36.10%), respectively and clay (9.40% and 11.86%) while Dampar series has low sand content (21%). Consequently, Dampar series depicted highest soil moisture content (18.80%) compared to Rasau and Kuah with high content of silt and clay at 42.43% and 36.43%, respectively. At tasseling stage, where application of P fertilizer with combination of ethephon at 0 and 15 kg P 2 O 5 ha-1 there were significant difference between soil series on root length, total biomass wet and dry weight but exception for total biomass dry weight at 0 kg P 2 O 5 ha-1. Moreover, at 45 kg P 2 O 5 ha-1 there were significant difference among soil series on leaf number and total biomass dry weight whereas at highest P rate of 60 kg P 2 O 5 ha-1 only root length and root volume were affected. Most of the results were observed highest on Rasau soil series which contain highest sand particle instead of silt and clay compared to Kuah and Dampar series. However, the addition of ethephon and several P rates did not affect plant height among soil series. The results suggest that, the marginal soil can be utilized for sweet corn production by addition of combined P fertilizer at low rate and PGR.

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