Greenhouses simulate the "desired" environment for successful growth and development of plants. They, by design, achieve this desired environment by supplying the necessary climatic inputs needed by the plants to strive and at the same time exclude factors impeding the growth of plants, hence it is called a controlled environment. One of the common and most desired attribute of the greenhouse is its ability to provide effective cooling to the plants. This paper reviewed, extensively, the concept of evaporative cooling as applied in greenhouses. Factors like Vapor Pressure deficit (VPD), Relative Humidity, Ambient Temperature were also discussed with regards to its effects on the efficiency of the evaporative cooling system. The efficiencies of the Fan and Pad System and the Fog systems were reviewed and compared with their consequent dependence on factors like nozzle spacing, nozzle length, saturation efficiency of pad material etc. The Natural Ventilation method was also reviewed as a "stand alone " greenhouse cooling method and as an augmentation to other cooling systems. Factors like rate of air exchange, total area of vents, wind speed, vent opening angles etc. were also discussed in line with their effects on the effectiveness of the Natural ventilation method. The Nigerian Perspective on Greenhouses and its Cooling methods was also discussed with reference to local development of evaporative coolers as well as its importation, its affordability, management, availability and appliance to the Nigerian farming culture.

No abstract

No abstract

No abstract

Cone penetrometers standardized by American Standards for Agricultural Engineering (ASAE) have been major instruments for investigating and quantifying soil compaction. However, the continuous use of penetrometers often introduces errors to the Cone Index (CI) readings obtained from the instruments over time. An ASAE calibrated digital cone penetrometer and a manual penetrometer were tested on a sandy clay loamy soil at the National Centre for Agricultural Mechanization (NCAM), Ilorin, Nigeria; using the ASAE small cone. The CI readings obtained for the two penetrometers were subjected to a statistical t-test. The results showed that the sensitivity of the manual cone penetrometer is comparable to that of the digital penetrologger at depths greater than 12cm as the mean difference showed no significant difference at this depth. However, at depths 0-11cm, there was significant difference in their mean difference; this shows the relative insensitivity of the manual cone penetrometer. The calibration results also showed that the continuous use of the manual cone penetrometer will require a multiplying facto r of 1.165 to get a CI reading close to ideal. Improvement on the manual cone penetrometer will also assist in obtaining CI readings after tillage operations.