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ThesisItem Open Access Investigation on allelopathic influence and control of purple nuts edge(Department of Agronomy, College of Agriculture, Vellayani, 1999) Ameena, M; KAU; Sansamma, GeorgeLab and field experiments were conducted at the Instructional farm, College of Agriculture, Vellayani to study the allelopathic influence of Purple nutsedge (Cyperus rotund us L) on important field crops; to investigate the effectiveness of systemic herbicides for control of nutsedge and also to assess the effect of chemical weed control on growth and yield of subsequent field crops. In Ex. no. I, allelopathic influence of purple nutsedge on important field crops like rice, ragi, cowpea, green gram, bitter gourd and bhindi were studied. The treatments comprised of aqueous extracts and blended extracts of fresh and dry plant parts of nutsedge. The results revealed that aqueous extracts of nutsedge inhibited germination of rice, ragi, bitter gourd and bhindi while it had some stimulatory effect on germination of cowpea and green gram. The early growth characters of the field crops were found suppressed by the aqueous extract treatment while the blended extract showed no effect. In general, the dry plant parts showed greater effect than the fresh material. Under Ex.no.Il, field studies were made to investigate the effectiveness of systemic herbicides viz. Glyphosate and 2,4-D for control of nutsedge. The treatments included different doses of the herbicides with and without adjuvants and Glyphosate combined with sublethal dose of 2,4-D. The results revealed that lowest dose of the herbicides were sufficient for complete kill of the purple nutsedge plants in the experimental area and there was no regrowth upto 6 weeks. There was significant reduction in viability of tubers collected one month after herbicide application, but the tubers tested 45 days after spraying showed an increase in germinability over the record on 30th day. Tubers from treatments involving Glyphosate with sublethal dose of 2,4-D recorded the lowest sprouting percentage indicating the possibility for weed control for a longer period. In Ex. no. In, the persistence of the herbicides in soil were monitored and it was observed that early growth of cucumber sown on the same day of herbicide application was affected while that sown on soils collected 10 days after spraying recorded growth characters comparable to that of control. From Ex.no.IV, it could be inferred that chemical weed control did not show any deleterious effect on growth and yield characteristics of ragi and cucumber sown 15 days after the treatments. Application of 2,4-D for nutsedge control was found superior to other treatments in terms of net income and B:C ratio and the lower unit cost of the chemical was precisely the reason for its superiority.ThesisItem Open Access Standradisation of organic and inorganic fertiliser comnbinations for maximising productivity in bitter gourd (Momordica Charantia L.)(Department of Agronomy, College of Agriculture, Vellayani, 1999) Rajasree, G; KAU; Raghavan Pillai, GAn investigation was carried out during 1995-96 and 1996-97 at the Instructional Farm attached to College of Agriculture, Vellayani to study the efficacy of different levels of N applications (200, 250 and 300 kg N ha") in different ratios of organic - chemical N substitutions (l : 1, 1:2 or 2: 1) at different frequencies (F I - full quantity of organic source as basal, F2 - organic source at basal and at 40th and 70th DAS, F3 - organic source as basal + fortnightly equal splits and chemical N source as basal + fortnightly intervals in equal splits in all the frequencies) of application. Two different organic sources ie. farm yard manure and poultry manure were used in two simultaneous experiments viz. Experiment I and 11. The experiments were separately and simultaneously laid out as confounded 33 design in 9 plot blocks with 2 replications, confounding LR2F in RI and LRF2 in R 11. Higher levels ofN nutrition was found to reduce days taken to flower in farm yard manure applied trial while sex ratio was narrowed at 90 DAS in poultry manure applied experiment. Higher jassid population was noticed at 60 DAS when higher levels ofN was supplied predominantly through organic source as farm yard manure. Fungal leaf spot infestation was higher with the application of200 kg N at 90 DAS and was also more with split applications of both farm yard manure and chemical N source at early stages of growth. Full basal application of poultry manure was found to promote the per hectare yield of fruits, fruit yield planr I and number of fruits planr I compared to its split applications. When highest level ofN (300 kg) was supplied through 2: 1 ratio of organic - chemical N substitution using poultry manure as organic source, it effectively increased the fruit yield and number of fruits plant". 2 Shelf life of fruits at room temperature was more when nutrient N was supplied through 2: 1 ratio of organic - chemical N substitution using farm yard manure or poultry manure as an organic source. When N level was increased beyond 200 kg, shelf life of fruits at room temperature slightly decreased even when it was predominantly supplied through organic source of farm yard manure or poultry manure. Similar trend was noticed at refiigeratory condition too. Nitrogen nutrition showed depressing effect on ascorbic acid or vitamin-C content of fruits in Experiment I. Iron content in fruits was more with the application of 200 or 300 kg N level in Experiment ll. When 300 kg N was applied through a major source of poultry manure (2: 1 ratio) it produced higher iron content in fruits. Higher nitrogen levels or nitrogen nutrition through 2: 1 ratio of substitution promoted the soil bacterial population in both Experiment I and II. Full basal application of farm yard manure or poultry manure favourably influenced the soil bacterial population. Nitrogen nutrition showed depressing effect on fungal population of soil in Experiment I while it stimulated the fungal growth in Experiment 11. Soil actinomycetes population was higher with 2: 1 substitution ratio using farm yard manure as organic source ofN. When farm yard manure or poultry manure as organic source was used in equal or higher proportion with chemical N source, it showed moderating effect on the soil acidity. Full basal application of farm yard manure also enhanced the soil pH from the acidic range and the organic carbon content. Application of higher levels ofN increased the net loss ofN, P and K of soil in both the Experiment I and H. Net loss ofN was higher with 1:2 ratio ofN substitution or few or more split applications of organic source (farm yard manure) in Experiment 1. Net loss of nutrients was moderated during the second year of field experimentation. Nitrogen 3 nutrition in 1:2 ratio of substitution enhanced the net loss ofN in Experiment H. Nitrogen nutrition through 2: 1 ratio ofN substitution or basal + 2 split doses of farm yard manure increased the net loss of P in soil. The net loss of K in soil was more when farm yard manure and chemical N sources were applied in 2: 1 or 1: 1 ratio of substitution. Net gain of K was observed in Experiment H, when chemical N source was substituted in higher proportion compared to poultry manure or when full dose of poultry manure was applied as basal dressing. Higher levels ofN application have resulted in negative net energy returns or energy loss in both the experiments. The 1: 1 or 1 :2 ratio ofN substitution caused higher net energy losses in Experiment I while split applications of poultry manure resulted in more energy loss in Experiment H. Total energy output was higher with full basal application of poultry manure in Experiment I. Energy ratios registered a negative value and was higher with low level ofN application in Experiment I and II. Higher gross returns were obtained when full quantity of poultry manure was applied as basal dose in Experiment 11. Application of300 kg N through 2: 1 ratio of organic- chemical N substitution registered higher gross returns in Experiment II. Net returns was higher when 200 kg N ha! was applied. Increasing N level beyond 200 kg was not economic in Experiment I using farm yard manure as organic source. When full quantity of poultry manure was applied completely as basal dose, higher net returns was obtained in Experiment H. Benefit-cost ratio decreased when N level was enhanced beyond 200 kg ha' in Experiment I. Higher benefit - cost ratio was recorded when poultry manure was applied in full dose as basal dressing. Study revealed the favourable influence of organic sources; farm yard manure and poultry manure on fruit quality, shelf life and soil properties. The suitability of poultry manure as organic source for vegetable cultivation was also established by this study.ThesisItem Open Access Nutrient management for yield improvement of transplanted rice in the southern region of Kerala(Department of Agronomy, College of Agriculture, Vellayani, 1999) Sudha, B; KAU; Chandini SAn experiment entitled "Nutrient management for yield improvement of transplanted rice (Oryza sativa L.) in the southern region of Kerala" was conducted at Cropping Systems Research Centre (CSRC) Karamana, during the kharif season of 1998 to study the efficacy of organic manures in conjunction with varying levels of NPK nutrients and sulphur in enhancing rice yield using the variety Kanchana. The experiment was laid out in 33 partially confounded factorial RBD with two replications. Combinations of three levels each of organic manures (M), inorganic NPK fertilizers (F) and sulphur (S) constituted the treatments. FYM @ 5 and lOt ha-l as well as vermicompost @ 5 t ha-l included the different manure levels. The normal NPK rates of 70 : 35 : 35 kg ha-l and enhanced rates of 87.5 : 43.75 : 43.75 and 105 : 52.5 : 52.5 kg ha-l were the three fertilizer levels. The different S levels were no sulphur, S @ 12.5 and 25 kg ha-1 Higher order interactions of MFS and M2FS were confounded in Rep I and Rep 11 respectively. Results of the field experiment revealed that the main effects of organic manures, chemical fertilizers and sulphur as well as their combinations exerted significant positive influence on most of the growth and yield attributing characters of rice. The higher NPK levels upto 105 : 52.5 : 52.5 kg ha-l and S levels of 25 kg ha-l were found significantly superior to lower levels. Organic manuring with FYM @ 10 t ha-1 and vermicompost @ 5 t ha-1 were found to be equally good in influencing growth and yield of rice. The available NPK status of soil after the experiment was maintained well above the initial status. The available sulphur status of soil was found to be considerably reduced in treatments which didn't receive sulphur addition. FYM levels recorded better benefit : cost ratio over verrnicompost addition. Increase in NPK levels upto 105 : 52.5 52.5 kg ha-l and sulphur addition @ 12.5 kg ha-l was found profitable. The combination of 5 t ha-l FYM along with the highest NPK level of 105 : 52.5 : 52.5 kg ha-I and S @ 25 kg ha-I recorded the highest B : C ratio, but this was comparable to that obtained with the combined effect of 5 t ha-l FYM, NPK @ 87.5 : 43.75 : 43.75 and S @ 12.5 kg ha-I.ThesisItem Open Access Phosphorus use efficiency and productivity as influenced by microbial inoculants in vegetable Cowpea(Department of Agronomy, College of Agriculture, Vellayani, 1999) Meena Mary, Mathew; KAU; Shahul Hameed, S MAn experiment was conducted at the Instructional Farm attached to the College of Agriculture, Vellayani during December 1998 - April 1999 with the objectives of finding out the role of bioinoculants viz. arbuscular mycorrhizal fungi (AMF) and phosphate solubilising microorganisms (PSM) in improving the phosphorus use efficiency and productivity in vegetable cowpea var. Sharika. The experiment was laid out in 3 x 4 + 2 factorial randomised block design with three replications. The treatments included three levels of microbial inoculants and four levels of phosphorus along with two control treatments. The study revealed that crop failed to show a significant response to the use of bioinoculants and phosphorus levels in a soil with low available nitrogen and medium phosphorus status. Biometric characters except length of vine at vegetative stage was influenced by phosphate solubilising microorganisms as well as dual application of PSM and AMF. Phosphorus application as well as interaction effect did not show a positive response on growth parameters except LAI at harvest stage where in interaction effect was significant. Bioinoculants and phosphorus application exerted a profound influence on root length and volume. Dual inoculation of AMF and PSM significantly improved root length and volume. Phosphorus application at all levels improved root mass where as maximum root length and volume were reco;ded at P2 level. Interaction effects were significant only with respect to root volume and root mass. Mycorrhizal colonisation percent was highest with M3P2 (AMP + PSM + 15 kg P20S ha-I) and showed a decreasing trend with higher doses of phosphorus. Microbial inoculants showed only limited role in improving yield and yield attributes. In general, crop responded positively to phosphorus application only up to 30 kg P20S ha-I but it was on par with 15 kg P20S ha-I. Among the interaction effects, dual application of AMP + PSM along with 30 kg P20S ha-1 gave the highest yield. The effect of microbial inoculants in promoting growth and yield of crop was found to decline in the presence of higher doses of applied phosphorus. Quality characters of pod viz. protein and fibre content were significantly improved by bioinoculants and graded doses of phosphorus. Dual inoculation of AMP and PSM significantly increased protein content as well as reduced fibre- content of pod . . Available nitrogen content in soil after harvest did not show any significant variation among treatments but bioinoculants significantly improved residual K20 content in soil. Available P20S content at vegetative, flowering and harvest stages recorded higher values compared to initial status. Treatments M3 and P2 recorded the maximum available P20S content at vegetative and flowering stages. But at harvest stage, lowest residual P20S content was recorded at P3 level indicating higher uptake by the crop at later stages. Interaction effects were significant with respect to P20S content only at vegetative stage. The results of economic analysis revealed that the net income and benefit-cost ratio was maximum by dual inoculation of arbuscular mycorrhizal fungi and phosphate solubilising microorganisms along with a phosphorus level of30 kg P20S ha-I.ThesisItem Open Access Emergence and competition of polla in semi-dry rice(Department of Agronomy, College of Horticulture, Vellanikkara, 1999) Renu, S; KAU; George Thomas, CSacciolepis interrupta (Willd.) Stapf. is a serious weed opthe semi dry rice in Kerala. An investigation focussing on the emergence pattern and growth characteristics of Sacciolepis and its management were undertaken at the Agricultural Research Station, Mannuthy during the early Kharif of 1999. Sacciolepis interrupta was found to emerge during the first few weeks after the initial ploughing followed by pre-monsoon showers. Majority of the weed seedlings (87%) emerged during the first two weeks. The emergence pattern supports the possibility of practicing a stale seed bed. in the management of the weed. Seeds collected during July 1998 remained dormant for initial six to seven months. The seed germination commenced by the month of March and attained a peak during June and July. The study on the competitiveness of Sacciolepis interrupta modified by stale seed bed technique was conducted during the first crop season using split plot arrangement in randomised block design (early Kharif) of 1999. The study revealed that competition from Sacciolepis alone could reduce the rice grain yield by 50.1 per cent. The Sacciolepis compete with the crop and reduced the height, LAI, tiller production and biomass production of the crop. Adoption of stale seed bed method reduced the competition from all weeds including Sacciolepis. Stale seed bed with paraquat application was found to be better than stale seed with hoeing. Application of oxyfluorfen @ 0.15 kg ai ha-1 as preemergence spray though reduced the problem of Sacciolepis in the semi-dry rice, could not prevent germination of other weeds beyond 15 DAS. However, as preemergence application of oxyflourfen prevented germination of all type of weeds in the beginning, it could save one hand weeding. From the study, it could be concluded that the practice of stale seed bed technique is an efficient tool for the management of Sacciolepis interrupta in semi-diy rice. The practice was found to be economically viable also.ThesisItem Open Access Intensive fodder production under irrigated condition in partial shade(Department of Agronomy, College of Agriculture, Vellayani, 1999) Romy, Jacob; KAU; Lakshmi, SA field experiment was conducted in the upland coconut gardens of Instructional Farm, College of Agriculture, Vellayani, Thiruvananthapuram, Kerala, to study the potential of intensive fodder cultivation under shaded condition. The influence of irrigation, FYM and fertilizers on the yield and quality of fodder and the effect of grass cultivation on the physico-chemical properties of soil were studied. 'The economics of irrigated fodder production was also worked out. The investigation was conducted for a period of one year from July 1998 to June 1999. The results revealed that irrigation at 30 and 45 mm CPE improved the growth parameters like plant height, tiller number uu', Leaf: Stem ratio and Leaf Area Index of congosignal and gave higher green fodder as well as dry fodder yields. Application of 7.5 t ha" of FYM increased the plant height,tiller number hiWl and Leaf Area Index. The uptake of plant nutrients viz., N, P, K, Ca and Mg by congosignal was favoured by irrigation. Application of FYM was not found to enhance the nutrient uptake, but, chemical fertilizers improved the uptake of nutrients by congo signal. Soil physical properties like bulk density, water holding capacity and porosity were improved by grass cultivation. Irrigation and application of FYM and fertilizers improved the soil physical properties. Irrigation and FYM application increased the soil organic carbon content. Available P and K status of the soil was improved by irrigation, while available N status remained almost unchanged. FYM or fertilizer application did not change the available N, P and K content of soil upto 7.5 t ha-I ofFYM and 150 : 50 : 50 kg NPK ha-I. Irrigation improved the fodder quality in terms of crude protein content. There was no improvement in the quality of fodder by FYM or fertilizer application at the recommended doses. Irrigated congosignal crop depleted more moisture from the top 0 - 30 cm layer of soil. The rainfed crop extracted more water from deeper layers than the irrigated crop. Root growth of congosignal was favoured by irrigation. While considering the economics of fodder cultivation, 45 mm CPE irrigation treatment was found to be the best, when compared to treatments involving 30 and 60 mm CPE irrigation and the rainfed control. Highest benefit : cost ratio was recorded for the treatment combination : irrigation at 45 mm CPE and recommended doses of manures and fertilizers (FYM @ 5.0 t ha-I and NPK @ 150 : 50 50 kg ha-I) when congo signal was grown as an intercrop in coconut garden.ThesisItem Open Access Response of vegitable cowpea to nitrogen and potassium under varying levels of irrigation(Department of Agronomy, College of Agriculture, Vellayani, 1999) Geetha, V; KAU; Kuruvila VarugheseAn experiment was conducted at the Instructional Farm attached to the College of Agriculture, Vellayani in the summer season during 1999 to study the response of vegetable cowpea cv.Malika to nitrogen and potassium under varying levels of irrigation. The experiment was laid out in a 33 confounded factorial design confounding INK in replication I and INK2 in replication H. The treatments included three levels each of irrigation,nitrogen and potassium. The study revealed that the crop responded to irrigation,nitrogen and potassium levels. The growth characters like plant height,number ofleaves per plant and LAI were not significantly influenced by the different treatments. But the earliness in flowering and the main yield attributing character viz., the number of rods per plant were favourably influenced when irrigation was given at a CPl ~ value of zuuun with a depth of 1 Omm water through micro sprinkler method. The earliness in flowering and number of pods per plant were also influenced when nitrogen and potassium were applied at the rate of20 kg ha-1 as compared to the other levels. The maximum yield of green pods was obtained when the crop was irrigated through micro sprinklers at 20mm CPE with a depth of 10mm water. The nitrogen and potassium levels at 20 kg ha-1 also enhanced pod yield. The haulm yield was not influenced by any of the treatments or its combinations. I The uptake of nutrient was influenced by the treatments. The nitrogen uptake was influenced only by variation in N levels. Potassium uptake was affected by the influence of both Nand K. Irrigation treatments influenced the uptake ofP205 alone at a single growth stage. Water use efficiency was highest whenirrigation was given through micro sprinkler. Nitrogen and potassium levels each at 20 kg ha-1 resulted in highest WUE compared to the other two levels. Moisture depletion was higher from the top 0-15 cm layer of the soil when the crop was irrigated at 10mm CPE with a depth of 20mm water through micro sprinkler. At 15-30cm and 30-45 cm depth surface method recorded the highest moisture depletion. Higher levels of potassium was found to influence the moisture depletion pattern. The available soil nutrient status after the experiment was influenced by nitrogen alone. The application of 40kg N ha! resulted in the highest available soil nitrogen content after the experiment. Irrigation and potassium excel red a remarkable influence on the proline content of the leaves. The maximum proline con (I: nt was recorded will 11 the crop was irrigated through micro sprinklers and potassium was applied at the rate 0 f 'Il' kg ha-I. The results of economic analysis revealed that the net returns was maximum by irrigating the crop through micro sprinkler. However, the BCR was highest when irrigation was given by surface method and at a nitrogen and potassium level of20 kg ha-1 each.ThesisItem Unknown Forage and seed production of signal grass (Brachiaria decumbens Stapf.) under different management practices(Department of Agronomy, College of Agriculture, Vellayani, 1999) Sonia, V K; KAU; Raghavan Pillai, GA field experiment was conducted in the Instructional Farm, College of Agriculture, Vellayani to assess the forage and seed production potential of signal grass under open conditions. The effect of varying levels of nitrogen, potassium and cutting management on the yield and quality of fodder and on the seed production potential of the grass were studied. The investigation was carried out for a period of one year from July 1998 to July 1999. The results revealed that nitrogen applied at the rate of 200 kg ha! improved the growth parameters like plant height, tiller number per hill and leaf number per hill. Potassium showed no significant response on growth parameters. The green fodder and dry fodder yields were favourably enhanced by nitrogen application. Nitrogen had a favourable effect on the number of days to attain 50 per cent flowering. Other yield attributes like number of seeds per panicle, seed yield and thousand seed weight were favourably . influenced by all the main treatment effects viz., nitrogen, potassium and cutting management. 2 Nitrogen exerted significant influence on leaf area index in the later harvests. Maximum leaf area index was noticed in the second harvest stage. The treatment with highest level of nitrogen alone influenced seed germination significantly. Application of nitrogen as well as potassium reduced the nitrogen content of the fodder. Potassium application resulted in a significant increase in potassium content of forage. Incremental levels of nitrogen reduced the crude fibre content. Potassium application resulted in a decreasing trend in crude protein content. The calcium and magnesium contents increased by potassium application alone. Incremental levels of applied potassium exerted a reducing effect on calcium and magnesium content of fodder. The K : (Ca+Mg) ratio of the fodder increased with increase in levels of applied potassium. The available nitrogen status of the soil was improved by nitrogen application. The available potassium status of the soil declined with increase in applied nitrogen while higher potassium levels substantially enhanced the available K status of soil. Considering the economics of fodder cultivation, highest B:C ratio was realised for the treatment which received the highest dose of nitrogen and potassium .ThesisItem Unknown Nutritional balance analysis for productivity improvement of rice in iron rich lateritic alluvium(Department of Agronomy, College of Horticulture, Vellenikkara, 1999) Bridgit, T K; KAU; Potty, N NInvestigation entitled “Nutritional balance analysis for productivity improvement of rice in iron rich lateritic alluvium” consisting of seven experiments was conducted during 1995-1997 in the farm attached to the Agricultural Research Station, Mannuthy. Objective of the study was to identify the factors that limit the productivity of rice in the lateritic alluvium, estimate the nature and extent of their influences, formulate and test the methodology to overcome them and to evolve high – tech management programme to get 6 t or more yield of grain per hectare. The study included evaluation of the influences of all the cultural and nutritional inputs on the content and balances of N,P,K,Ca,Mg,S,Fe,Mn,Zn, Cu and SiO2 in the root, culm and leaf at MT and PI and boot leaf in addition to uptake in grain and straw. Results revealed the following Field evaluation of the crop performance in 36 locations of Thrissur and Palakkad districts of Kerala spread in km2 and three soil types revealed that yield ranged from 2800 to 9000 kg ha-1. Low productivity was not due to real deficiency of any of the 11 elements in the foliage. Foliar concentrations of individual elements were more than what has required to produce yield levels above 7000kg ha-1 in some locations expect for silica. Low realized yields were found to be due to the excess plant contents of non-applied elements especially Fe, Mn,Zn and Cu as well as their interactions in plants. As such, soil test or tissue test values of elements were found inadequate, a “content balance combined approach” was found to be better tool in nutritional management. Iron content of the root of the order of 50,000 ppm under submerged conditions was found to inhibit morphological and physiological development leading to low yield. Physiologically, lower development of chlorophyll ‘a’ and its poor stability as well as a higher sap PH lead to low dry matter accumulation. Morphologically the effect was expressed through very few long roots at MT,low root weight, root damage and failure of further initiation of roots, protracted production of fewer tillers as well as their decline and low dry matter accumulation in the shoots between MT and flowering periods. Yield variation due to the early suppression alone was of the order of 1800 kg ha-1. Harmful effects of Fe in the plant was less subsequently as Fe decreased progressively with growth of the plant. Manganese and Zn and to some extent Cu found to take over from Fe in the post panicle initiation phase. Leaf concentrations of these elements at PI and flowering stages rise far higher the critical levels. Manganese was found to reduce photosynthetic efficiency at this stage and Zn was identified with affecting translocation to the grain from vegetative parts in the maturity phase, thereby affecting translocation to the grain from vegetative parts in the maturity phase, thereby affecting grain – straw ratio. Lower productivity of second crop (September – October compared to first crop (April – May seeded rice) was found to be due to the higher foliar concentrations of Mn and Zn in the PI stage onwards. Cultivation under continuous submergence aggravated these inhibiting influences. Thus low yield of rice in laterite soils was found to be due to a multi – element multiphase effect. Nutritionally these effects could be recognised through narrow N/Fe, N/Mn, K/Fe, K/Zn ratios. Application of Ca @ 150 kg lime ha-1 could reduce the Fe content of the plant and S at 100 kg ha-1 could reduce Mn and Zn content in the plant at PI. Substituting urea with Ammonium sulphate for top dressing appeared to be better to contain Mn and Zn at PI stage. Application of SiO2 at 250 kg ha-1 and increasing the levels of K from the present level of 45 kg to 120 kg ha-1 and resorting to dry seeding in April-May crop and wet seeding in October-crop and irrigation once in three days after disappearance of ponded water were found to be effective means of containing the low yield malady and raise the yield beyond 6 t ha-1. This production programme has the advantage that it does not involve much additional input, offers the scope of reducing P application by 50 per cent and scientifically sustainable as it keeps nutrient removal within the levels of application of N, P and K. This programme also offers a way to progressional yield improvement above 6 t ha-1 as the levels of Fe, Mn and Zn in the leaves are still far higher than suggested critical levels.
