Abstract:

Khasi mandarin (Citrus reticu/ata Blanco), is a major fruit crop in Meghalaya. However, due to the factors like, poor fertility, soil acidity, erosion, etc. the productivity is found to be low The present study was conducted to diagnose the reason of low productivity of the orchard of khasi mandarin so that proper rejuvenation program can be proposed. The orchard of the Umsning area is a privately owned orchard having distinct difference in the productivity and health of plants along the different slopes. Since, Meghalaya receives heavy rainfall, it was also anticipated that the heavy downpour may have some role in loss of nutrients through leaching anderosion. The orchard was divided into three reaches i.e., lower, northern and southern reaches, five plants from each reach were randomly selected for collecting of soil samples at three depths i.e., 0-15, 15-30 and 30-45 cm. Soil samples were collected from three spots around the root zone (50 cm away from the base of trunk) and samples were also collected in March (premonsoon) and October (post-monsoon). Soils were analyzed for fertility indices and acidity indices.The study indicated that the soils were highly acidic in reaction with low pH (4.62), exchangeable Ca2+ and Mg2+ (4.47 meq/100g soils), exchange acidity (1.67 meq/100g soils), exchangeable Al3+ (0.90 meq/100g soils), cation exchange capacity (7.54 meq/100g soils), percent Al3+ saturation (12.04 %), percent base saturation (62.34 %), soil organic carbon (1.34 %), available nitrogen (254.50 kg/ha), available phosphorus (20.74 kg/ha), available potassium, (209.35kg/ha), available Sulphur (37.24 kg/ha). The two way ANOVA indicated that lower reach, which represented very poor yielding treesare significantly (Po.o5) different from northern reach and southern reach in all important parameters. The PCA also showed as lower reach a separate group in all the indices, in both pre-monsoon and post-monsoon seasons at 0-15 cm depth. However, at 15-45 cm depth the parameters did not form any distinct cluster during post-monsoon season. It is, nevertheless, confirmed that lower reach should be treated differently from northern reach and southern reach for rejuvenating program. The pair wise correlation indicated that the yield is positively influenced by pH, Calcium and Magnesium, organic carbon, percent base saturation and negatively influenced by Aluminium, exchange acidity. It can be concluded that yield of khasi mandarin in this orchchard was strongly influenced by low pH, high Aluminium and exchange acidity. The leaf nutrient content analysis however did not yield any significant difference slope wise in the orchard that indicated that plants in the orchard taken up at par irrespective the slope. From the present investigation, it is evident that lower reach of the orchard was more affected by soil acidity which is directly influencing the yield and the yield of Khasi mandarin orchard was highly determined by the soil acidity factors (Ca2+ and Mg2+ and AI3+). So, we can conclude that the rejuvenating programme for Khasi mandarin orchards should be slope specific considering the soil acidity and fertility indices. Further to make soil nutrient available to the plants, soil amelioration programme may be considered for reducing soil acidity which will directly translate into increase of production of the crops.