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Open Access
Effect of different inputs on productivity and quality relations in njavara (Oryza sativa)
(Department of Agronomy, College of Horticulture, Vellanikkara, 1996) Meera Menon, V; Kau; Potty, N N
Productivity characteristics of Njavara (Oryza sativa), a medicinal rice variety were investigated based on the results of four separate experiments conducted at the Regional Agricultural Research Station, Pilicode, during 1994-96. The experiments were to study (i) growth and development characteristics (ii) crop weather relations (iii) response to nitrogen, phosphorus and potassic fertilizers and (iv) the effect of integrated nutrient management. Two biotypes of Njavara, the black glumed and golden yellow glumed, were tested in the first two experiments. The black glumed biotype alone was studed in the third and fourth experiments. The first experiment, consisting of the two biotypes as treatments, was conducted in wetland, open upland, heavily shaded upland and partially shaded upland, and pooled analyses of the data were conducted. Treatments of the second experiment which studied the effect of date of sowing on productivity of Njavara included 10 dates of sowing at fortnightly intervals starting from the 15th of May. Combinations of three levels of nitrogen, phosphorus and potassium, each at levels of 15, 30 and 45 kg ha-1 along with a standard and absolute control constituted the treatments of Experiment III. The last trial consisted of two treatments, one exclusively with farmyard manure and another with fertilizer alone, both at 30 kg nitrogen equivalent, two treatments with organic and inorganic manure in different ratios and three combinations of Azospirillum with 25, 50 and 75 per cent of the full farmyard manure dose. The second experiment was conducted in open upland and the third and fourth experiment in heavily shaded coconut gardens. Biometric, nutritional and quality criteria estimated through accepted methodology were used for the evaluation of treatments. An abstract of the results obtained has been presented in the following paragraphs. The results showed that three phases could be distinguished in the growth and development of Njavara. They are a primary phase of absorption and accumulation of nutrients, a grand growth phase of rapid accumulation of dry matter and a diversion phase when the seed and quality develop. Continued growth till harvest gave high yield and dry matter decline in the final phase led to superior quality characteristics. Golden yellow glumed biotype exhibited continuous growth and higher yield of grain. Black glumed biotype manifested dry matter decline in the final phase, leading to lower yield of grain and higher free amino acid content in the grain. Profound influence of cropping situation on yield and quality of grain was observed. Lowest yield of 684 kg ha-1 and highest amino acid content of 0.492 mg g-1 were observed in the uplands and highest yield of 2401 kg ha-1 and lowest amino acid content of 0.203 mg g-1 were observed when Njavara was sown in the wetlands. Viewed on the basis of variation in nutrition in the different situations, the results showed that yield limiting influences were not the deficiency of any element but the excess contents of Mg and Mn at maximum tillering and of P, K, S, Zn and Cu at panicle initiation stages in the plant. This appeared to be a highly significant result in the context of stagnant productivity of crops like rice. Content of free amino acids in the grain appeared to be unique characteristic of Njavara rice. Among the amino acids, sulphur containing amino acids, methionine and cysteine were also present. Possibly, these amino acids are related to the medicinal value of Njavara in the treatment of rheumatic complaints, the symptoms of which resemble thiamin deficiency. Inherently high yield potential of Njavara was expressed in the date of sowing trial. Both the biotypes recorded grain yields of 6000 kg ha-1 when sown on most favourable dates. Weather influence contributed to be highest yield through two ways, firstly, by increasing the total dry matter yield and secondly, by improving the grain-straw ratio. The golden yellow glumed biotype produced higher grain yield than the black glumed biotype. Application of N, P and K fertilizers increased the uptake of all the elements studied. Positive interaction of fertilizer elements on content and uptake of elements was also evident. However, application of fertilizers could influence only the straw yield significantly. One possible reason for the absence of significant improvement of grain yield by fertilizer application appeared to be due to the high levels of application. Even 15 kg ha-1 of N, P and K were found to be excess in shaded situations. Results of the integrated nutrient management studies showed that level of application was more important than the source in affecting the ultimate yield. Farmyard manaure application led to a more balanced development of the components of yield whereas fertilizer source improved only the floret number per panicle. Nutritional management at levels below 15 kg ha-1 N equivalent significantly reduced the yield. Azospirillum did not have any effect in increasing the yield of Njavara. The results of the different experiment brought out the role of soil and atmosphere environment as well as the biotype influence on the yield and contributed to the development of the concept of soil-plant-atmospheric continuum on the technical side. On the pracical side they showed that Njavara is an ideal crop for growing in the first crop season in the uplands in North Malabar when no other crop can be grown and that growing in heavily shaded uplands will give high quality grain. Advantageously, the crop will not require intense management.
Open Access
Ecophysiology and management of Isachne in rice fields of Onattukara
(Department of Agronomy, College of Horticulture, Vellanikkara, 1996) Abraham, Varughese; KAU; Tajuddin, E
Isachne miliacea Roth is the most dominant weed in the 28,000 ha of low land rice fields of the coastal sandy Onattukara region, situated in Kollam and Alapuzha districts of Kerala. A serious of investigations were undertaken at Rice Research Station, Kayamkulam, during 1991 to 1994 with the objective to identify the major weeds in the rice ecosystem and to bring out the ecophysiology of 1. Miliacea and to find out a suitable weed management strategy for the rice based cropping system of Onattukara. Isachne miliacea was found to be the dominant weed in rice during Kharif and Rabi seasons. The weed seeds germinate in April – May, attains its peak vegetative growth in July and flowers in October. The seeds mature in November and the plants dry off in January with the onset of summer. The weed is propagated by seeds and stem cuttings. Germination of seeds can be prevented by submerging the seeds in the area in water even to a depth of one centimetre. The forcing of the stem cuttings of 1. Miliacea to a depth of five centimetre below the soil surface or maintaining a submergence for more than five centimetre can effectively check the vegetative multiplication of the weed. Seeds attained physiological maturity in November and remained dormant upto March. Seeds of the season that remain on the surface germinate fully in April – May with the pre – monsoon showers while the buried seeds remain dormant. Burying the seeds to more than five centimetre depth and water stagnation in July to November induced secondary dormancy. Viability of the seeds was lost faster at shallow depth of burial. Crop weed competition studies were conducted in Kharif and Rabi for two years with different densities of 1. Miliacea. Weed competition was severe in dry dibbled Kharif compared to wet transplanted Rabi. Even a small density of five 1. Miliacea plants per square metre produced appreciable biomass and reduced the DMP of rice substantially. Integrated weed management study was conducted in Kharif and Rabi for two years in a split – plot design in three randomised blocks. Kharif season treatments formed the main plots for Rabi trial. In Kharif five pre – emergence herbicides were compared with local practice. Local practice of hoeing on 15 DAS and HW twice on 25 and 40 DAS gave maximum grain yield. Application of oxyfluorfen 0.1 kg ha-1 followed by HW on 30 DAS was on par with local practice and ranked second. The performance of other herbicides anilofos 0.40 kg, butachlor 1.25 kg and thiobencarb 1.25 kg per hectare were also satisfactory when followed by one HW on 30 DAS. Pretilachlor 0.50 kg ha-1 was phytotoxic to rice. The tested herbicides effectively controlled 1. miliacea upto harvest of rice compared to local practice. During Rabi the effect of pre-plant spray of glyphosate and hand weedings were compared. Among the treatments a pre – plant spray of glyphosate after harvest of Kharif controlled 1. miliacea best and gave maximum rice yield in Rabi season. Kharif treatments did not show any significant influence on yield of rice during Rabi. From the study it could be concluded that pre – emergence spray of oxyfluorfen 0.1 kg ha-1 followed by one HW on DAS in Kharif and pre – plant application of glyphosate 0.75 kg ha-1 on residual weeds immediately after the harvest of the Kharif crop gave efficient weed control and economic yield of rice in the rice based cropping system involving rice – rice – fallow of Onattukara region.
Open Access
Inter-relationship of applied nutrients on growth, productivity and latex flow characteristics of havea brasiliensis muell. arg.
(Department of Agronomy, College of Agriculture, Vellayani, 1993) Punnoose, K I; KAU; Sreedharan, C
Three field experiments were conducted in three locations representing the major rubber growing regions in South India to study the response to nutrient applications on growth characters, yield and latex flow characteristics and to study the inter-relationship between soil and plant nutrients on yield. It was also envisaged to assess the relative response in the different locations and to make economic analysis of the benefit of manuring. Three levels of 0, 40 and 80 N ha-1, 0, 30 and 60 kg P2O5 ha-1 and 0, 40 and 80 kg k2O ha-1 and two levels of 0 and 10 kg MgO ha-1 were used. A 33 x 2 partially confounded factorial split plot experiment in randomised block design with two replications was followed. The 80 kg level of N and 30 and 40 kg levels respectively of P and K were optimum for girth increment in all the locations. Application of Mg was also beneficial. For virgin bark thickness the 40, 30 and 40 kg levels of N, P and K respectively were sufficient in all the locations and application of Mg was not beneficial. For bark renewal 80 kg N was optimum at Thodupuzha whereas the 40 kg level was sufficient in the other locations. The 60 kg level of P was useful at Kulasekharam and Thodupuzha while 30 kg was sufficient at Balussery. The 40 kg level of K was optimum in all the locations and application of Mg was not beneficial. The 80 kg level of N gave the maximum weight of leaf litter in all places while for P and K the 30 and 40 kg levels respectively were sufficient. Magnesium was beneficial only at Balussery in one year. The 40, 30 and 40 kg levels respectively of N, P and K gave the highest total volume of latex in all the locations except at Balussery where 80 kg K was superior to 40 kg. Application of Mg was beneficial at Balussery while it had a reducing effect at Kulasekharam and no effect at Thodupuzha. Application of N and K reduced the plugging index and that of P and Mg increased it in all the locations. For dry rubber content, the 80 kg level of N was optimum at Kulasekharam while the 40 kg level was sufficient in the other locations. With regard to P and K the 30 and 40 kg levels respectively were sufficient. Application of Mg was beneficial only at Thodupuzha. In the case of yield of rubber 40 kg N and 30 kg P2O5 were found to be optimum in all locations. The 40 kg level of K2O was sufficient at Kulasekharam and Thodupuzha while the 80 kg gave the highest yield at Balussery. At Thodupuzha and Balussery application of Mg was beneficial while at kulasekharam it reduced the yield. Application of N increased the organic carbon content of soil. The available P, K and Mg contents of soil were increased by the application of the respective nutrients. The N, P, K and Mg contents of leaf and latex were increased by application of the respective nutrients. Application of P as rock phosphorus also increased the available Ca content of soil and Ca contents of leaf and latex. The yield of rubber was positively correlated with girth increment, rate of bark renewal, initial flow rate, total volume and dry rubber content of latex and negatively with plugging index. Yield was also positively correlated with the available N, P, K and Ca contents of soil N, K and Ca contents of leaf and P and K contents of latex and negatively correlated with Mg contents of soil and leaf. The strongest correlations with yield were given by soil N, latex P and K and leaf Ca. Total volume of latex was positively correlated with the available N, P, K and Ca contents of soil, N, K and Ca contents of leaf and P and K contents of latex. The dry rubber content of latex was positively correlated with the available N, P and Ca contents of soil, N, K and Ca contents of leaf and N, P, K and Ca contents of latex. The plugging index was positively correlated with the P and Ca contents and negatively with the N and K contents of soil, leaf and latex. Positive correlations, were obtained between soil and leaf nutrients, soil and latex nutrients and leaf and latex nutrients in the case of N, P, K and Ca. In the case of yield of rubber 40 kg N and 30 kg P were found to be optimum in all the locations. The 40 kg level of K was sufficient at Kulasekharam and Thodupuzha while the 80 kg level gave the highest yield at Balussery. Application of Mg was beneficial at Thodupuzha and Balussery while at Kulasekharam it reduced the yield. An overall evaluation of the economic analysis indicated that 40 kg N, 30 kg P2O5 and 40 kg K2O were the optimum doses in all the three locations. Application of Mg was profitable only at Thodupuzha.
Open Access
Rice based cropping system analysis in kerala
(Department of Agronomy, College of Agriculture, Vellayani, 1993) Chidananda Pillai, M R; KAU; Sreedharan, C
With the objectives of identifying the most economic crop combination for the double crop wet rice fields of Kerala and to assess soil fertility changes due to rice based cropping systems and also to find out the residual effects of the summer crops on the succeeding rice crops an investigation was conducted at the R.A.R.S. Pattambi in a split – split plot design, for a period of two years. The salient findings of the investigation are as follows. In the Cassava-rice-rice system 25 per cent saving was recorded for P and K for maximum grain yield of kharif rice than the recommended doses. A saving of 50 per cent each of P and K was recorded for the maximum straw yield than the recommended doses. In cowpea–rice-rice system for maximum grain yield of kharif rice there was a saving of 25 per cent of P and K than recommended doses. The same trend followed for the maximum yield of strew also. In groundnut –rice-rice system, for maximum grain yield of kharif rice there was a saving of 25 per cent of P and K than recommended doses. For the production of maximum straw yield full dose of recommended nutrients were required. In bhindi– rice-rice system for maximum grain yield of kharif rice there was a saving of 50 per cent of P and K than recommended doses. For the production of maximum straw yield full dose of recommended nutrients were essential. In rice-rice-rice system for maximum grain yield a saving of 25 per cent of P and K was recorded than recommended doses. For the production of maximum straw yield full dose of recommended nutrients were required. In fallow-rice-rice system for maximum grain yield full dose of recommended nutrients were essential, whereas for the production of maximum straw yield a saving of 25 per cent of P and K than the full dose was recorded. In cassava, rice and fallow systems for the manifestation of residual effect to the rabi rice, balanced nutrients at high doses are to be applied to the preceding kharif crop where as in the cowpea, groundnut and bhindi systems, residual effects of nutrients are seen manifested to the rabi rice crop even when the kharif rice crop is applied with medium doses of nutrients. There was a trend of slight decrease in the organic carbon content of the soil under all the cropping systems. The status of available nitrogen and potash after one and two year crop sequences also followed the above trend. Regarding the status of phosphorus in the soil, there was a slight increase after one and two year crop sequences. Cassava system produced maximum yield in terms of energy value followed by groundnut. From the economic point of view bhindi system gave the maximum net return. Maximum dry matter production (biomass production potential) was recorded in the cassava system followed by groundnut system. A vegetable crop like bhindi or a tuber crop like cassava seem to be more profitable than growing rice in summer season in the double crop wet rice fields of Kerala, rice being least economic. Among the cropping systems rice-rice-rice system generates maximum employment opportunities for the farm labourers with maximum job opportunities for women labourers as well.
Open Access
Effect of cover crops on nutrient dynamics in the rubber plantations
(Department of Agronomy, College of Agriculture, Vellayani, 1995) Prathapan, K; KAU; Sreedharan, C
Three field experiments were conducted at Bethany Estate, Mukkampala, Kanyakumari District from February 1991 to October 1993 to study the effect of cover crops on the nutrient dynamics in immature, mature rubber plantation and an open area. In Experiment I there were two cover crops viz. Pueraria phaseoloides and Mucuna braceata and five levels of NPK viz. 0:0:0, 0:30:30, 10:30:30, 0:60:60 with one year old RRII-105, replicated thrice and statistically laid in RBD. In Experiment II there was one cover crop Mucuna sp alone with five levels of NPK as above with 8 years old RRII-105 replicated 4 times and statistically laid in RBD. In Expt. III there were 10 microplots, with both cover crops. N, P, K, Ca, Mg content of both Hevea and cover crops were increasing as the crops growth progressed. Fertilizer application to cover crops improved the Hevea leaf nutrient content than the absolute control. Among the levels 10:30:30 was found optimum. Mucuna was found better than Pueraria in increasing the Hevea leaf nutrient content. Girth increment was better with 10:30:30. This was found to be optimum under both experiments. More height increment was observed in this level, as well as in cover cropped treatments when compared to absolute control. Biomass production of cover crops were maximum at 10:60:60 followed by 10:30:30 under both experiments. Biomass production, root weight and length were higher in Mucuna and it was found increasing as the crop growth progressed. Nodule count was higher in Pueraria and the fresh weight of nodule per plant was higher in Mucuna as the size of its nodule was found bigger. Soil Moisture retention capacity was found higher under cover cropped plots at both shallow (0-30cm) and deeper (30-60cm) soil depths at-0.033 and -1.5 Mpa pressures than control. Pore space and aggregation percentage were improved whereas bulk density decreased. Among the levels of NPK 10:30:30 was found optimum in improving the soil physical properties. The percentage of improvement was found greater at shallow depth of soil than deeper. Soil moisture content during summer months were improved in the cover cropped area. The soil moisture in than the top soil (0-30cm) was lesser than the bottom soil (30-60cm) in Pueraria grown plots. This trend was reverse in the case of Mucuna. Growing of cover crops improved the microbial population of bacteria, fungi and phosphate solubilising organisms. The level 10:30:30 was found optimum for the better microbial activity. 10:30:30 was found optimum for better yield and Latex Flow Characteristics. Covercropping has increased the latex yield by 15-20%. 10:30:30 was optimum for better leaf litter production of Hevea. In cover cropped plots the leaf litter production was higher and wintering was delayed by 26-30 days over the control. This has enhanced 10 additional tapping days. Girth is positively correlated with cover crop biomass, nutrient uptake, soil available nutrients, soil moisture contents and Hevea leaf nutrient contents. Strongest correlation for girth was found with Hevea leaf N content, and uptake of N by cover crops, suggesting the importance of foliar diagnosis. Yield was negatively correlated with Mg content of soil.
Open Access
Nutrient- moisture interaction under phasic stress irrigation of sweet potato in summer rice fallows
(Department of Agronomy, College of Agriculture,Vellayani, 1994) Muraleedharan, Nair; G, KAU; Muraleedharan, Nair; v
A field experiment on sweet potato was laid out in the rice field fallowed during summer season at the Instructional Farm, College of Agriculture, Vellayani. The study was intended to work out of the irrigation schedule and fertilizer practice for sweet potato grown as a catch crop during the summer season of 1990 and 1991. The experiment was designed to economise the use of irrigation water as well as fertilizers by inducing phasic stress at certain phases of plant growth which are considered critical for sweet potato. The field experiment was laid out in a strip plot design replicated thrice with irrigation in horizontal strips and fertility levels in vertical strips. Irrigation water at full CPE was given during tuber initiation phase (10-30 DAP), full CPE at tuber maturity phase (80-100 DAP) and full CPE at tuber initiation and tuber maturity phases. The crop received irrigation at ½ CPE during the rest of the period of plant growth. Nitrogen and potassium were applied @ 25, 50 and 75 kg ha-1 and a uniform dose of P2 O5 @ 50 kg ha-1 and lime @ 500 kg ha-1 were applied. A control plot that received NPK @ 75:50:75 kg ha-1 and FYM @ 10 t ha-1 was maintained for treatment comparison. Growth characters were recorded at an interval of 21 days from planting and it was observed that providing irrigation at full CPE during tuber initiation phase resulted in significant increase in vine length and number of leaves plant-1. Enhanced rate of application of Nitrogen promoted the growth of vines, number of branches plant-1 and number of leaves produced plant-1. Potassium did not exert any influence on these growth characters. Growth analysis studies showed that the LAI was maximum in plots that received irrigation at full CPE during tuber initiation phase. Nitrogen substantially influenced the LAI, higher levels being significantly superior to the lower levels. Higher levels of potassium also influenced the LAI. The NAR and specific leaf weight were the highest in plots that received irrigation at ½ CPE during tuber initiation phase. Both NAR and CGR were high in the early stage of plant growth and decreased towards harvest. Increased rates of nitrogen supply decreased the NAR and specific leaf weight whereas no definite trend could be observed on CGR> Higher levels of potassium had a favourable influence on NAR and CGR. The dry matter of leaves, shoots, fibrous roots and tubers were significantly enhances by providing full CPE during tuber initiation phase. Increasing the level of nitrogen, influenced the dry matter in the aerial parts. The influence of K on dry matter production was not consistent. Tuber bulking rate showed a positive trend under irrigation at full CPE during tuber initiation phase. Nitrogen levels at 50 and 75 kg ha-1 had an overlapping influence on tuber bulking rate and both remained superior to 25 kg ha-1. Scheduling of irrigation did not exert any influence on the length and girth of tuber. However, an increase in the length and a corresponding decrease in the girth were noticed at enhanced rates of nitrogen supply. The number of tubers plant-1 showed a significant improvement by providing irrigation at full CPE during tuber initiation phase. The total number of tubers plant-1 was increased by high rates of N, but did not influence the number of marketable tubers. Application of K at 50 kg ha-1 promoted the production of more tubers. Tuber yield was significantly influenced by irrigation wherein providing full CPE during tuber initiation phase resulted in superior yield of both total and marketable tubers. Tuber yield was maximum at 50 kg ha-1 each of nitrogen and potash. Vine yield was significantly enhanced by higher rates of applied nitrogen. The harvest index and utilization index were enhanced by the application of irrigation water at full CPE during tuber initiation phase. Application of N at 25 kg ha-1 resulted in the production of high starch content whereas the sugar content was increased upto the highest level of 75 kg ha-1. The uptake of nitrogen by vines and tubers showed a progressive increase by applying full CPE during tuber initiation phase. Application of higher levels of nitrogen invariably promoted the uptake of N, P and K by the plant. Application of potash at 50 or 75 kg ha-1 also resulted in higher uptake of potassium. The fertility status of the soil did not show a positive trend by scheduling of irrigation. The plots that received the lowest dose of nitrogen, invariably recorded the highest level of available phosphorus. Available potassium content was also high in plots that received higher rates of potash. Irrigation at full CPE during tuber initiation and/or tuber maturity phase recorded significantly higher water use efficiency and net returns as compared to including stress during tuber initiation phase. Nitrogen and potash both at 50 kg ha-1 recorded the maximum water use efficiency and net returns from sweet potato cultivation.
Open Access
Weed management in sole and intercropped coconut gardens
(Department of Agronomy, College of Horticulture, Vellanikkara, 1990) Savithri, K E; KAU; Sreedharan, C
Field experiments were conducted during the period from 1986 to 1989 at the Agricultural Research Station, Mannuthy, Thrissur to develop weed management practices for sole and intercropped coconut gardens. There were three fields trials. In trial - I the treatments comprised of three manual methods (digging once, digging twice and sickle weeding), six chemical methods (paraquat three sprays, glyphosate 0.4 kg ha-1, glyphosate 0.8 kg ha-1 dalapan followed by paraquat, paraquat + diuron and paraquat followed by glyphosate), two combinations of manual and chemical methods (2,4-D + diuron immediately after sickle weeding and glyphosate followed by digging) were compared with weed free and unweeded control in underplanted coconut garden. In trial - II, the treatments comprised of two manual methods (spade weeding and sickle weeding ), one cultural method (growing cowpea as an intercrop) two cultural + chemical methods (cowpea followed by paraquat or glyphosate), three pre-emergence herbicides + post-emergence herbicide (diuron followed by paraquat, oxyfluorfen followed by paraquat and atrazine followed by paraquat ) were compared with weed free and unweeded control in coconut+ banana cropping system. Unweeded control in coconut banana cropping system was compared with that in sole crop of coconut . In trial III, the treatments tried in coconut+banana cropping system were eveluated in sole crop of banana and there were thirteen treatments . All these three trials were laid out in Randomised Block Design and replicated thrice.
Open Access
Effect of nutrition as Influenced by irrigation on growth and yield of oil palm (Elaeis guineensis Jacq)
(Department of Agronomy, College of Agriculture, Vellayani, 1994) Thomas, Varghese P; KAU; Sreedharan, C
A field experiment was conducted in the oil palm plantations of the Central Plantation Crops Research Institute (CPCRI) Research Centre, Palode, Kerala to study the response of mature oil palm to fertilizer and irrigation applications with respect to growth, yield and uptake of nutrients. There were four levels of fertilizers viz: F0- 0:0:0, F1-600: 300: 600, F2- 1200: 600: 1200 and F3-1800: 900: 1800 g N : p20 : k20 palm-1 year-1. The three levels of irrigation were: I0-no irrigation, I1-45 1 palm-1 day-1 and I2-90 1 palm-1 day-1. The 4x3 factorial experiment was laid out in randomised block design with three replications. The study was also envisaged to establish the importance of leaf nutrient ratios of yield group of palms and its application in identifying nutrient limitations through the Diagnosis and Recommendation Integrated System (DRIS) approach in oil palm. The influence of various climatic parameters on yield of oil palm was studied by relating the monthly yield of oil palm in the field experiment with the monthly weather variables as far behind as 42 months before harvest. Fertilizer application of 1200 g N+600 g P2O5+ 1200 g K2O palm-1 year-1 was found to improve the growth characters such as annual leaf production, number of leaves on the crown, dry matter production of leaf, trunk and bunches, total dry matter production and the crop growth rate. Increase in yield attributes such as number of female inflorescences, sex ratio, average single fruit weight and the number of bunches at F2 level contributed to the significantly high FFB yield at F2 level of fertilizer application. Both palm oil and palm kernel oil production were also maximum at F2 level. For the uptake of nutrients N,P and K by palm parts as well as by the palm as a whole, the F2 level of fertilizer application was found to be the optimum. It was observed that 79% of the total uptake of N, 77% of P and 82% of K are removed annually through leaves and bunches from the system. A K-Mg antagonism was also detected in nutrient uptake. The yield of palm was found positively correlated with leaf production, leaf area, net assimilation rate, number of bunches produced, vegetative dry matter, P and K in soil and the total uptake of N, P and K by the palm. Both net income and benefit cost ratio were also found favorable at F2 level of fertilizer application. Irrigation at I2 level has resulted in increased leaf production, leaflets per leaf, leaf area, leaf dry matter, mesocarp dry matter and the bunch dry matter. Physiological parameters like relative water content, leaf water potential, stomatal resistance, leaf temperature and net photosynthesis were all favourable at I2 level of irrigation. Female flower production, sex ratio, single fruit weight and number of bunches produced were also more in I2 treatment. This has resulted in increasing FFB production at I2 level. Palm oil production was also more at I2 level. Total uptake of N, P, K and Ca were also found to be maximum at I2 level of irrigation. The net profit and benefit cost ratio were also maximum at I2 level. Leaf nutrient ratios of palms in different yield groups: were used to evolve parameters and norms for Diagnosis and Recommendation Integrated System (DRIS) in oil palm. The range of nutrient ratios within the zones of balance, moderate imbalance and imbalance were determined which were also illustrated through DRIS charts for three nutrient combinations. The DRIS approach was used to evaluate the nutrient balancing of the different treatments of the field. The order of relative importance of the five nutrients was determined using nutrient imbalance index (NII) values as indicated below: K> P> N> Mg> Ca The F2 level of fertilizer application in the experiment was found to be the most balanced among the tested fertilizer levels. The possibility of magnesium becoming a potential limiting nutrient at higher levels of fertilizer application has been brought out from the study. The superiority of balanced nutrition in increasing total dry matter production and bunch yield became evident from the study. The studies on climatic relationship with yield revealed that the pattern of variation in monthly yield remained the same inspite of irrigation throughout the summer months. The relationship of monthly yield of oil palm with monthly climatic parameters was evaluated up to a period 42 months before harvest. When eight climatic parameters were considered together, the influence of these weather parameters at seven specific lag periods viz. 1-4, 9-10, 13-16, 20-23, 25-28, 32-33 and 37-40 were found important for oil palm. Of these the lag 25-28 was found to be the most important as the relationship of climatic parameters with yield at this period was more. Relative humidity, maximum temperature and rainfall were identified as the most important variables influencing palm yield. Using results obtained from regression studies yield prediction models were constituted. It is concluded that yield prediction using the three or more variables is possible for oil palm 26-28 months in advance of harvest. The salient findings from the study is that a fertilizer dose of 1200g N+ 600 g P2O5+ 1200 g K2O palm-1 year-1 and irrigation level of 90 l palm-1 day-1 applied through drip system during the summer months are required to obtain maximum FFB yield from mature oil palm. The order of importance of nutrients for oil palm is determined as K> P> N> Mg> Ca. With the above level of fertilizer application the palms were found to have a more balanced nutrition. However continued application of fertilizers might possibly lead to magnesium deficiency unless corrective measures are adopted. Relative humidity, maximum temperature and rainfall are found to be the most important climatic parameters influencing oil palm yields. The influence of climatic parameters at seven lag periods 1-4, 9-10, 13-16, 20-23, 25-28, 32-33 and 37-40 were found to be more pronounced on palm yield. From these studies it became possible to predict oil palm yields 26-28 months in advance using models based on these weather parameters.
Open Access
Agronomic evaluation of biofarming techniques for forage production in coconut gardens
(Department of Agronomy, College of Agriculture, Vellayani, 1996) Sansamma, George; KAU; Raghavan Pillai, G
Two field experiments were conducted at the Instructional Farm, College of Agriculture, Vellayani, Thiruvananthapuram, Kerala State to study the potential of biofarming techniques for forage production in coconut gardens. The study was carried out for a period of two years from September 1993 to August 1995. The influence of the different nutrient management techniques on uptake of nutrients, quality of produce and physico-chemical properties of soil was also investigated. In experiment no.1. the influence of two nitrogen fixing organisms., viz. Azospirillum and Azotobacter and the role of Vesicular Arbuscular Mycorrhiza (VAM) in improving the growth and production of guinea grass and congosignal was studied under inoculation alone and also in combination with chemical fertilizers. The nitrogen fixers were tested under varying levels of fertilizer nitrogen and for VAM the level of phosphorus varied between treatments. The prospects for vermicompost use for guinea grass production was examined under experiment no. 2. It was also envisaged to compare the impact of integrated use of manures and fertilizers with the continuous use of chemical fertilizers alone. Results of experiment no.1 revealed that Azospirillum inoculation alone and in combination with fertilizers had significant positive influence on guinea grass production. Azotobacter inoculation showed only limited effects on growth and yield of the forage grass during the first year but the effect was significant during the second year. The results indicated that 25 per cent of the recommended nitrogen could be saved through the use of either of the biofertilizers. VAM inoculation when combined with full dose of recommended fertilizer nitrogen and potassium, showed significant superiority over the POP treatment at 0, 25 and 50 per cent phosphorus doses while the 75 percent P dose gave comparable yields. The quality parameters of the forage recorded values on par or superior to that of the recommended fertilizer treatment. The use of biofertilizers improved the net income and benefit : cost ratio from guinea grass cultivation. The inoculation treatments were found to have a favourable influence on the physical and chemical properties of the soil. Integrated use of the nitrogen fixing organisms with chemical fertilizers was found effective for Congosignal cultivation. Pooled analysis studies indicated that when inoculated with either Azospirillum or Azotobacter, 50 per cent of the recommended fertilizer nitrogen was adequate for yields. VAM inoculation alone elicited significant yield increase over the absolute control. Combind doses of VAM with chemical fertilizers at all levels of applied phosphorus responded more or less similar to the recommended fertilizer treatment. This indicated the possibility of completely substituting the need for fertilizer phosphorus in VAM inoculated congosignal. The VAM effect in promoting growth and yield of the forage was found to decline in the presence of applied phosphorus. The data on economics also favoured the use of biofertilizers. Experiment no. 2 revealed that guinea grass responded well to integrated use of manures and fertilizers. As per pooled analysis vermicompost @ 5 t ha-1 or Farm yard manure @ 10 t ha-1 when combind with 75 per cent of the recommended NPK were comparable with the 100 per cent NPK treatment. Application of the organic manures improved the quality of the produce. The physic-chemical properties of the soil was also favourably influenced by the integrated use of manures and fertilizers. The economic analysis of the data emphasised the need for reducing the reliance on purchased inputs. Coconut yield was found favourably influenced by intercropping of the fodder grasses.

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