الفهرس 
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Abstract
Two field experiments were conducted in the Agricultural Research Station at Arab El-Awamer, Assiut Governorate, during the two growing seasons of 2014 and 2015 to investigate the response of grain sorghum to NPK fertilization in new reclaimed land. The randomized complete block design using split-split-plot with four replications was employed, where nitrogen fertilizer rates (100, 120 and 140 kg N/fed.) were allocated in the main plots, while phosphorus fertilizer rates (22.5 and 30 kg P2O5/fed.) were assigned in the sub-plots and potassium fertilizer rates (24 and 36 kg K2O/fed.) were fixed in the sub-sub-plots. The grains of sorghum variety Hybrid 305 was sown on 13th and 17th June in the first and second seasons, respectively. The plot area was 12 m2 including 4 ridges of 60 cm apart with 4 m length.
The results could summarized as the following:
I – Growth traits:
1- Plant height (cm):
- The plant height had a highly significantly affected by nitrogen and phosphorus fertilizer rates, while K fertilizer rates did not significant in both seasons.
- The tallest plants were recorded by 120 kg N/fed and 30 kg P2O5/fed. in both seasons, as well as by 24 or 36 kg K2O/fed. in the 1st and 2nd seasons, respectively.
- The first and second order interactions exerted a highly significantly influenced on the plant height tin both seasons, except NxK interaction did not significant in the 1st season.
- The first order and second order interactions (100 kg N x 30 kg P2O5/fed.), (120 kg N x 24 K2O/fed.), (30 kg P2O5 x 36 kg K2O/fed.) and (100 kg N x 30 kg P2O5 x 24 K2O/fed.) in the 1st season, as well as (120 kg N x 22.5 P2O5/fed.), (120 kg N x 24 K2O/fed.), (30 kg P2O5 x 24 K2O/fed.) and (120 kg N x 30 P2O5 x 24 K2O/fed.) in the 2nd season gave the tallest plants.
2 – Stem diameter (cm):
- The stem diameter exerted highly significantly influenced by nitrogen and phosphorus fertilizer rates in both seasons, while potassium fertilizer rates in both seasons did not significant effect on the stem diameter.
- The thickest stems were obtained by 140 kg N/fed., 22.5 kg P2O5/fed. and 36 kg K2O/fed. in both seasons.
- The stem diameter had significantly affected by NxP, PxK and NxPxK interaction treatments in both seasons.
- The first order and second order interactions (140 kg N x 30 kg P2O5/fed.), (22.5 P2O5 x 36 K2O/fed.) and (140 kg N x 30 P2O5 x 24 kg K2O/fed.) in the 1st season, as well as (100 kg N x 22.5 P2O5/fed.), (22.5 kg P2O5 x 36 kg K2O/fed.) and (100 kg N x 22.5 P2O5 x 36 K2O/fed.) in the 2nd season declared the highest mean values for stem diameter.
3- Leaf area index (LAI):
- The nitrogen, phosphorus and potassium fertilizer rates had significantly effect on the LAI in both seasons, except phosphorus fertilizer in the 1st season and potassium fertilizer in the 2nd season did not significant effect on LAI.
- The highest mean values for LAI were stated by 140 and 100 kg N/fed., 30 and 22.5 kg P2O5/fed. and 36 kg K2O/fed. in the 1st and 2nd seasons, respectively.
- The NxK and NxPxK interactions in both seasons and PxK interactions in the 2nd seasons had significantly effect on LAI.
- The highest mean values for LAI were achieved by the 1st and 2nd order interactions treatments (140 kg N x 36 K2O/fed.) and (140 kg N x 22.5 P2O5 x 36 kg K2O/fed.) in the 1st season, as well as (100 kg N x 36 kg K2O/fed.), (22.5 P2O5 x 24 K2O/fed.) and (100 kg N x 22.5 P2O5 x 36 K2O/fed.) in the 2nd season.
4- Number of days to 50% flowering:
- The number of day to 50% flowering exerted significantly influenced by nitrogen, phosphorus and potassium in both seasons, except potassium fertilizer did not significant effect on number of days to 50% flowering in the 2nd season.
- The best values for number of days to 50% flowering were observed by 140 kg N/fed.; 30.0 and 22.5 kg P2O5/fed. and 36 and 24 kg K2O/fed. in the 1st and 2nd seasons, respectively.
- The number of days to 50% flowering had a highly significant effect on NxP and NxK interactions in both seasons and PxK interaction in the 1st season and then NxPxK interaction in the 2nd season.
- The best values for number of days to 50% flowering were detected by the first and second order interactions treatments (140 kg N x 30.0 P2O5/fed.), (140 kg N x 36 kg K2O/fed.), (30.0 P2O5 x 24 kg K2O/fed.) and (140 kg N x 30.0 P2O5 x 36 K2O/fed.) in the 1st season, as well as (140 kg N x 30 P2O5/fed.), (120 kg N x 24 K2O/fed.) and (140 kg N x 30 P2O5 x 36 K2O/fed.) in the 2nd.
II- Yield attributes and yield traits:
1- Panicle length (cm):
- The panicle length had a highly significantly affected by nitrogen fertilizer rates in both seasons and phosphorus and potassium fertilizer rates in the 2nd season.
- The longest panicles were recorded by 100 and 120 kg N/fed. in the 1st and 2nd seasons, respectively, as well as by 30 kg P2O5/fed. and 24 kg K2O/fed. in the 2nd season.
- The all first order interactions i.e. NxP, NxK and PxK interactions exerted highly significantly influence on panicle length in both seasons, except NxK interaction did not significantly effected on this trait in the 2nd season, as well as the NxPxK interaction exerted significantly on this trait in both seasons.
- The longest panicles were mentioned by the first and second order interaction treatments i.e. (100 kg N x 22.5 kg P2O5/fed.), (100 kg N x 24 kg K2O/fed.), (22.5 kg P2O5 x 24 kg K2O/fed.) and (100 kg N x 22.5 kg P2O5 x 24 kg K2O/fed.) in the 1st season. Also (100 kg N x 30 kg P2O5/fed.), (30 kg P2O5 x 24 kg K2O/fed.) and (100 kg N x 30 kg P2O5 x 24 kg K2O/fed.) in the 2nd season.
2 – Panicle width (cm):
- The nitrogen fertilizer had a highly significantly effect on the panicle width in the 2nd season only, and the widest panicles were recorded by 100 kg N/fed. in both seasons.
- The first order interactions i.e. NxP and PxK interactions in the 1st season and NxK interaction in both season declared a highly significantly effected on the panicle width.
- The highest mean values for panicle width were recorded by the 1st order interactions treatments (100 kg N x 22.5 kg P2O5/fed.), (100 kg N x 24 K2O/fed.) and (30 kg P2O5 x 36 kg K2O/fed.) in the 1st season, and by (120 kg N x 24 kg K2O/fed.) in the 2nd season.
3- Grains weight/panicle (g):
- The grains weight/panicle exerted highly significantly influenced by nitrogen, phosphorus and potassium fertilizer rates in both seasons, while phosphorus fertilizer did not significantly effect on this trait in the 1st season.
- The highest mean values of grains weight/panicle were noted by 100 kg N/fed. in both seasons, then by 30 kg P2O5/fed. in the 2nd season and by 24 kg and 36 kg K2O/fed. in the 1st and 2nd seasons, respectively.
- The all first and second order interactions i.e. NxP, NxK, PxK and NxPxK interactions showed a highly significantly effected on the grains weight/panicle in both seasons, except NxP interaction did not significant on this trait in the 1st season.
- The highest mean values for grains weight/panicle exerted by the 1st and 2nd order interactions treatments (100 kg N x 30 kg P2O5/fed.), then (100 kg x 24 K2O/fed.), then (22.5 kg P2O5 x 24 kg K2O/fed.) and by (100 kg N x 30 kg P2O5 x 24 kg K2O/fed.) in the 1st season, as well as by (100 kg N x 30 kg P2O5/fed.), then (100 kg N x 36 kg K2O/fed.), then (30 kg P2O5 x 24 kg K2O/fed.) and by (100 kg N x 30 kg P2O5 x 36 kg K2O/fed.) in the 2nd season.
4 – Number of grains/panicle:
- The nitrogen fertilizer rates had a highly significantly effect on the number of grains/panicle and the greatest values for number of grains/panicle were obtained by 100 kg N/fed. in both seasons, while the phosphorus and potassium fertilizer rates did not significantly effect on this trait in both seasons.
- The all first and second order interactions exerted a highly significantly influenced on the number of grains/panicle in both seasons, except PxK interaction had insignificant effect on this trait in the 2nd season.
- The greatest mean values for the number of grains/panicle were recorded by the 1st and 2nd order interaction treatments: (100 kg N x 22.5 kg P2O5/fed.), then (100 kg N x 24 kg K2O/fed.) and (100 kg N x 22.5 kg P2O5 x 24 kg K2O/fed.) in both season, as well as by (22.5 kg P2O5 x 24 kg K2O/fed.) in the 1st season.
5- 1000 grain weight (g):
- The nitrogen fertilizer in both seasons, phosphorus and potassium fertilizer rates in the 2nd seasons had a highly significantly effect on the 1000 grain weight.
- The heaviest 1000 grain were detected by 100 and 120 kg N/fed. in the 1st and 2nd seasons, respectively, as well as the heaviest ones were detected by 30 kg P2O5/fed. and 36 kg K2O/fed. in the 2nd season.
- The all first and second order interactions exerted a significantly or highly significantly effected on the 1000 grain weight in both seasons.
- The highest mean values for 1000 grain weight were obtained by the first and second order interactions treatments: (100 kg N x 30 kg P2O5/fed.), then (100 kg N x 36 kg K2O/fed.) and (100 kg N x 30 kg P2O5 x 36 kg K2O/fed.) in both seasons, as well as by (30 kg P2O5 x 24 kg K2O) and (22.5 kg P2O5 x 36 kg K2O/fed.) in the 1st and 2nd seasons, respectively.
6- Grain yield/fed. (ard.):
- The nitrogen fertilizer rates in both season had a highly significantly effect, as well as phosphorus and potassium fertilizer rates in the 2nd season had a significantly effect on the grain yield/fed.
- The maximum grain yield/fed. (ard.) were recorded by 100 and 120 kg N/fed. in the 1st and 2nd seasons, respectively, as well as by 30 kg P2O5/fed. and 36 kg K2O/fed. in the 2nd season.
- The NxP interaction in the 2nd season had significantly effect on the grain yield/fed. and the other 1st and 2nd order interactions i.e. NxK, PxK and NxPxK in both seasons exerted a highly significantly influence on the grain yield/fed.
- The maximum grain yield/fed. (ard.) were recorded by the 1st and 2nd order interactions treatments (100 kg N x 30 kg P2O5/fed.), then (100 kg N x 24 K2O/fed.), then (22.5 kg P2O5 x 24 kg K2O/fed.) and (100 kg N x 30 kg P2O5 x 24 K2O/fed.) in the 1st season, as well as by (120 kg N x 30 P2O5/fed.), then (120 kg N x 24 K2O/fed.), then (30 kg P2O5 x 24 K2O/fed.) and (120 kg N x 30 P2O5 x 24 K2O/fed.) in the 2nd season.