Measuring of pulling resistance in machinery with passive working organs

A determination of the total pulling resistance of machinery is important in light of its dimensioning as well in light of energy requirements of processed operation. There are several methods to determine it. They can be divided to analytical methods (Goryachkin) and to methods of measurement in field-laboratory conditions using different kinds of force sensors. The most frequently used type is a sensor on the base of tensiometer, which was used during our work. Measured pulling resistance at three working speeds and at ranges of used depths of soil processing 82−122 mm was 9.6−17.4 kN with variation coefficient up to 10%. This measure has proved a dependence of the total pulling resistance on used depth of soil processing however dependence on speed of operation was practically insignificant. Machinery work quality was evaluated by determination of weight of plants matter on the field surface and by quantification of its percentage in total plant matter on the same area. The measured percentage range of plant matter on the field surface was 67.2−4.6% at working speed 8−14 km/h.

Agronomic performance of maize (Zea mays L.) breeding lines derived from a low nitrogen maize population

Eighteen S1 lines of maize (Zea mays L.) derived from a low nitrogen tolerant pool and two inbred lines were evaluated for agronomic performance under moderate N conditions in the southern Guinea savannah of Nigeria. Generally, the breeding lines differed in yield, growth, vertical root-pulling resistance, N-uptake and N-use efficiency. Breeding lines with high vertical root-pulling resistance took up more N and utilized it more efficiently. They also showed better agronomic performance and recorded higher yields. Principal component and cluster analyses classified the breeding lines into six groups. The results of principal components analyses (PCA) suggest that the most important variables for the classification of the S1 lines were grain yield, plant height, total dry matter during the grain-filling period and at maturity, N-accumulation, N-uptake and N-use efficiency. Other important traits were days to silking, anthesis-silking interval, ears per plant, harvest index and vertical root-pulling resistance. Two groups containing a total of 14 S1 lines that had higher agronomic performance than others are recommended for further evaluation under severe N stress to ascertain their tolerance of low N stress before recombination to form a new population for the next cycle of selection.