RESEARCHES ON THE INFLUENCE OF SOWING DENSITY ON SWEET LUPINE YIELD

. Lupine is cultivated on quite limited areas in Romania, the information about the culture of this legume is scarce and may be one of the reasons why lupine is not found in the crop structure. Through the experience established, during 2016-2017, at the Turda Agricultural Development Research Station (ARDS), located in the hilly area of the Transylvanian Plain, the behavior of two varieties of white lupine (sweet) and the productivity of the plants under the influence of pedoclimatic conditions of the years 2016-2017 and some technological elements, in the present case - sowing density. Of the two varieties, the Romanian variety recorded a slightly higher yield than the variety of foreign origin. Lupine reacts positively to density of 15-22 pl/sqm, recording yields of 3828 kg/ha (22 pl/sqm) and 3223 kg/ha (15 pl/sqm), respectively. At the density of 11 pl/sqm the yield drops significantly. The rainfall deficit during the period of flowering-pod formation, calendrically the first half of June - the first half of August, also contributes to the decrease in yield.

For the entire experiment, sowing was carried out at a distance between rows of 45 cm, with the mention that only the distance between grains per row was different.
Bacterization of the seeds was carried out in the morning, three to four hours before sowing, using Nitragin lupine -bacterial culture of Bradyrhizobium lupini in a dose of 3 vials/ha. The predecessor plant was maize, the sowing of lupine was carried out experimentally every year in the second decade of April, and the harvest in the first half of September.
In the experimental field, no disease and pest control treatment applied. The weed control was carried out on the vegetation by two manual weeders, thus also contributing to the reduction of environmental pollution.
The lupine yield obtained from each experimental variant was weighed, transformed to STAS humidity (13%) and reported per hectare. The results obtained were statistically processed according to the method of analyzing the variant and establishing the lowest significant differences, LSD (5%, 1% and 0.1%) (ANOVA, 2015).The climatic conditions of the 2016-2017 experimentation period are presented in table 1 and 2 (source Turda Meteorological Station).

RESULTS AND DISCUSSION
Average monthly temperatures during the vegetation period are higher than the multiannual average in the two years studied (table 1), with the exception of May of 2016, when the deviation was negative, and April of 2017, when the monthly average of was equal to the multi-year average. The deviations from the multiannual average temperature are different from one month to another and are between -0.7ºC and 2.5ºC in 2016 and between 0ºC and 3.0ºC in 2017. The amount of precipitation recorded in the months of the vegetation period was in excess in 2016, but in 2017 the precipitation varied a lot, with an important deficit of precipitation being observed in the months of May, June and August (table 2). Of the two varieties analyzed, the Romanian variety recorded a yield of 3034 kg/ha, with an insignificant difference of 54 kg/ha higher than the variety of foreign origin, which is more adapted to the pedoclimatic conditions in our country (table 3). Lupine reacts very well to density of 15-22 pl/sqm, registering yields of 3828 kg/ha (22 pl/sqm) respectively 3223 kg/ha (15 pl/sqm), with very significantly positive differences from the variant where of 44 pl/sqm density was used. A very significant decrease (of -504 kg/ha) in yield was observed in the variant where a density of only 11 pl/sqm was used (Table 4). Compared to temperature, white lupine has higher requirements, preferring moist and warm springs, thus making better use of higher temperatures than other varieties of lupins. Although the average monthly temperatures in the two years analyzed were higher than the average, however, the temperature conditions in the growing season of the lupine were optimal for development, even if in the flowering-forming pods phase, the average monthly temperature in both years were higher by 2.0ºC (2016) and by 2.8ºC (2017) respectively compared to the multiannual average.
The climatic factor responsible for the optimal development of the crop is the amount of water available to the plant in the important phases, when the plant's requirements are higher, which is why the rainfall deficit during the period of flowering-formation of the pods, in 2017, led to an average yield of 2971 kg/ha, with 73 kg/ha less than in 2016 and with 36 kg/ha less than the average of the two years (considered a witness), the difference, however, is not statistically ensured (Table 5).  From the triple interaction shown in Table 6, it can be seen that the foreign variety cultivated at the density of 44 pl/sqm in 2016 registers a lower yield than the native variety, cultivated under the same conditions, with a significant difference of -455 kg/ha, and in 2017 this difference reaches -579 kg/ha, a distinctly significant difference from the native variety. Another decrease in yield, but not statistically ensured, is observed in the case of cultivation at the density of 11 pl/sqm, both in 2016 and in 2017.
The German variety registers yield increases, compared to the Romanian one, in the variants where it was sown at density of 22 pl/sqm respectively 15 pl/sqm, but the differences between 126-235 kg/ha in the case of the density of 22 pl/sqm and 132-215 kg/ha in the case of density of 15 pl/sqm are not statistically insured.

CONCLUSIONS
Of the two varieties analyzed, the native variety responds better to the climatic conditions of the two experimental years, obtaining a higher yield, but not statistically insured compared to the foreign variety.
The most significant yield increases are obtained at a sowing density of 22 pl/sqm, the variety of foreign origin reacting very well to this density. And the lowest yields are obtained at the density of 11 pl/sqm. Climatic conditions, especially precipitation, can influence the yield achieved, but if minimum climatic conditions are met and the technology is properly applied for the development of the crop, the lupine obtains high yields at a low cost.