Response of Cabbage ( Brassica oleracea var capitata ) to Organic and Inorganic Fertilizers on Growth and Yield Parameters and Incidence of Insect Pest

— Two field experiments were conducted for two cropping seasons at the Multipurpose Crop Nursery of the Akenten Appiah-Menka University of Skills Training and Entrepreneurial Development Mampong-Ashanti, from August to November, 2015and June to September, 2016 to determine the response of cabbage (Brassica oleracea var capitata) to organic and inorganic fertilizers on growth, yield and incidence of insect pest. The experimental design used for the field experiment was a randomized complete block design (RCBD) with three replications. The treatments were: poultry manure (20 t ha -1 ) + Cypermetrine (30 l ha -1 ), cow dung (20 t ha -1 ) + Cypermetrine (30 l ha -1 ), N.P.K (15:15:15) (300 kg) + Cypermetrine (30 lha -1 ), foliar + Cypermetrine (30 l ha 1 ), poultry manure (20 t ha -1 ) + neem leaf extract, cow dung (20 t ha -1 ) + neem leaf extract, N.P.K (15:15:15)(300 kg) + neem leaf extract, foliar + neem leaf extract and the control (no fertilizer and no insecticide). The result revealed that the application of organic manure (poultry manure and cow dung) and inorganic fertilization is a better option for soil fertility enhancement in cabbage production.High percentage crop establishment (>95%) was achieved across treatments with NPK + Cypermetrine, poultry manure + neem, N.P.K (15:15:15) + Neem or Foliar fertilizer + neem achieving 100% crop establishment. The application of Cow dung+ NLE produced the highest number of open leaves in both seasons. Application of poultry manure and N.P.K combined with Cypermetrine significantly improved head weight and cabbage yield.Application of poultry manure combined with Cypermetrine or neem leaf extract produced earliest head initiation and widest head diameter.In conclusion cabbage growers are encouraged to use poultry manure at 20 t ha -1 and N.P.K (15:15:15) (300 kg) combined with Cypermetrine at 30 l ha -1 and neem leaf extract for the improvement of cabbage growth, yield and incidence of insect pest.


INTRODUCTION
Cabbage demand is high on the Ghanaian domestic market, serving as a source of vitamin and mineral requirements as well as a major source of income to the youth and women in urban and peri-urban areas (Timbilla and Nyarko, 2004). The crop is high in water content, fibre, protein, calcium, iron, and vitamins A and C (Adeniji et al., 2010;Meena et al., 2010). The rise in the consumption of cabbage has necessitated the increase production of the crop in Ghana. However, the productivity of cabbage per unit area is rather low compared to other developed countries of the world. This is as a result of numerous production challenges faced by farmers. Notable among them are soil nutrient and pest management which are required for better growth and yield of cabbage. Nutrient supply is an important input for realizing higher cabbage yield and its nutrient content  (Snr et al., 2018). This makes it difficult for the local farmer to boost production and to increase yield, thereby reducing yield and their income levels. The habit of applying synthetic insecticides to control cabbage pest has been the traditional practice among most farmers in Ghana. The heightening consciousness of the danger associated with the use of synthetic insecticides as well as their high costs of control has necessitated for a less dangerous form of pest control. Organic pesticides have long been an alternative to synthetic chemical insecticides for pest control and management. This is because they pose little threat to the environment and to human health (Appiahet al., 2014).
Cabbage has high requirements for all nutrients, especially nitrogen and it demands for achieving high yields range from 130-310 kg/ha (Milas and Vincent, 2017). Nitrogen over-use in modern agriculture is of importance with respect to both environmental concerns and the quality of plant products. Cow dung is a potential source of nutrients and also a potential benefit to soil amelioration, especially for communal farmers who cannot afford fertilizers. However, getting maximum value out of the manure requires applying it at proper rates and frequency in conjunction to a particular soil (Pahlaret al., 2013).
The suitability and usefulness of cow dung has been attributed to high availability of N.P.K content and increased availability of organic matter content to degraded soil which may lead to the increasing activity of beneficial microorganisms and improves the physical properties of the soil (Snr et al., 2020). The plant has good responsiveness on animal manure application in quantity of 40 t/ha. Organic manuring enhances soil biological activity, improves nutrient mobilization, soil structure and increases soil water retention (Roy and Kashem, 2014). Crop production with integrated use of mineral and organic manure has proved to be highly beneficial by increasing yield as well as keep the environment sound. In the past, agricultural production was focused on maximizing the quantity of vegetables produced for commercial markets (Pavla and Pokluda, 2008); while in the last few decades the organic management of crops has gained popularity because of increased consumer's awareness of the health problems that come from food grown under conventional farming. Differences between organic manure and inorganic fertilizers, especially in soil fertility management may affect the nutritive composition of plants (Hassan and Solaiman, 2012). Shapla (2013) reported that manure applied in correct proportion, does not just improve soil porosity but it also contributes to good plant growth, development and yield, chlorophyll and N.P.K content.
In view of the benefits to the diet and the livelihood of the Ghanaian populace and to determine the effectiveness of fertilizers for soil improvement and maintenance on cabbage, it is of much importance to find out the response of cabbage (Brassica oleracea var capitata) to organic and inorganic fertilizers on growth and yield parameters and incidence of insect pest. The field was laid in a randomized complete block design (RCBD). There were nine (9) treatments with three replications. The nine treatments were made up of eight organic manure and fertilizer rates and the control (without amendment) and chemical insecticide (Cypermetrine) and neem leaf extract were assigned to each block. The treatments were: poultry manure (20 t ha -1 ) + Cypermetrine (30 l ha -1 ), cow dung (20 t ha -1 ) + Cypermetrine (30 lha -1 ), N.P.K (15:15:15) (300 kg) + Cypermetrine (30 l ha -1 ), foliar + Cypermetrine (30 lha -1 ), poultry manure (20 tha -1 ) + neem leaf extract, cow dung (20 t ha -1 ) + neem leaf extract, N.P.K (300 kg) + neem leaf extract, foliar + neem leaf extract and the control (no fertilizer and no insecticide).

Soil and manure application
Land clearing was by slashing and removing of stumps and this was immediately followed by lining and pegging. The experimental area was demarcated into plots and before transplanting, soil, poultry manure and cow dung were mixed thoroughly. Samples of nomanure soil (control) and organic manure (poultry manure and cow dung) was randomly taken prior to inorganic fertilizer application at a uniform depth of 0 -20 cm for chemical analysis. Soil and organic manure samples analysis were carried out at the Soil Research Institute of CSIR laboratory in Kumasi, Ghana. The characteristics analyzed for included pH in (1:1 soil: distilled water ratio) and measured by the potentiometric method on a pH meter manufactured by VebPracitron in Dresden, Germany. Organic matter was determined by the Walkey and Black methodand total nitrogen was determined by the micro Kjeldahl method. Exchangeable cations were determined by flame emission photometry. Extraction was carried out by filtration or centrifugation. Ca and Mg were determined using an atomic absorption or spectrometry (AAS) after the removal of ammonium acetate and organic matter at pH 7.0. The result on nutrient level of organic manure and soil chemical properties are shown in Tables 1 and 2.

Soil and manure chemical analysis
Samples of soil, organic manure and a mixture of soil and manure from the various replicates and treatments with the exception of DI'GROW (Foliar fertilizer) plot were taken for analysis at the Soil Research Institute, Kwadaso in Kumasi. The characteristics analyzed for included; soil pH, organic matter, organic carbon, total nitrogen, exchangeable calcium, magnesium, potassium and sodium, effective cation exchange capacity, total exchangeable bases and available phosphorus and potassium.

Land preparation, fertilization and planting
The land was cleared by slashing and removal of stumps, ploughed and harrowed and then lined and pegged for planting. Cow dung and the poultry manure were applied depending upon the treatment at the rate of 20 t ha -1 and worked into the soil two weeks before transplanting of cabbage seedlings. The inorganic fertilizer (N.P.K15:15:15) at the rate of 300 kg ha -1 was applied to the designated plots on the various replicates two weeks after transplanting. The cabbage variety used for the study was Oxylus. The seedlings were transplanted four weeks after nursing at a spacing of 50 cm x 30 cm and at a depth of 1.0 cm. Transplanting of seedlings for each season was done early in the morning. Each experimental plot contained four (4) rows and ten (10)

Data collection and analysis
The vegetative data collected were percentage plant establishment and number of open leaves. The percentage plant establishment was measured at 21 days after planting (DAT).This was achieved by counting the number of plants in the two middle rows per plot and the percentage crop establishment estimated. The number of open leaves was counted from the two middle rows per plot at two weeks interval from 21 DAT to 63 DAT. Days to head initiation, head weight per plant and head diameter were estimated from the two central rows. Days to head initiation was counted from transplanting date to first harvest day when heads were firm. Head diameter was measured from the middle portion of the head using the vernier caliper. Cabbage head from the two middle rows per plant at harvest were weighed for the determination of head weight (kg) per plant using electronic weighing scale. Harvest index was estimated by dividing the fresh weight of head by the above ground fresh biomass of the plant. The data collected were analyzed using Analysis of Variance (ANOVA).The data obtained were analyzed using GenStat Release 11 statistical package and the Least Significant Difference (LSD) was used to separate the means at 5 % level of probability.

Nutrient levels of organic amendments
Generally, the nutrient levels of the poultry manure applied in the 2015 cropping season was comparatively higher than the cow dung (

Soil Chemical properties before and after treatment application for 2015 and 2016 cropping seasons
In 2015, soil analysis before application of treatments indicated that the soil was slightly acidic with a pH of 6.13, whereas that of 2016 was moderately acidic with a pH of 5.70 (  Tables 2).Soil amendments improved percentage total N from the initial low levels to moderately high levels after the 2016 cropping season. While cow dung or poultry manure slightly improved organic matter, though still in the low category after the 2015 season, they significantly improved organic matter to the moderate or high levels after the 2016 cropping season. The application of cow dung left more organic matter in the soil in both years than the other amendments. Low levels of exchangeable cations, total exchangeable bases and effective cation exchange capacity were recorded for all treatments after both seasons, though slightly higher than the untreated (control). All the fertilized plots recorded moderate to high levels of available P or available K after both cropping seasons (Tables 2).
The differences in pH and nutrient levels of the organic manure in 2015 and 2016 could be due to differences in organic matter. It has been suggested that the growth of plants is optimal when soil pH is between 5.8 and 6.5 and sometimes to a maximum of 7.5 depending on the plant species (Ontario Ministry of Agriculture, 2009). The application of the poultry manure and cow dung allowed the soil pH fall within a range needed for maximum plant growth except for cow dung in 2016. The pH of the soil became acidic after the season because pH of the cow dung was acidic. This could be that the parent material for soil formation has a role to play in the overall pH of the soil formed. It has been established that soils respond differently to changes in pH depending on the soil's buffering ability (CEC) (Page-Dumroese et al. 2006). The initial CEC of the soil in 2016 before the application of the cow dung was low and this does not allow the holding of cations to the soil surfaces to aid in neutralization. Such soils are unable to control nutrient losses through leaching too.
The application of organic manure provides benefits of improved fertility, water holding capacity, structure, increased organic matter and organic carbon (Adebayo et al. 2011). Much organic matter and carbon was left on the cow dung treated plots principally because cow dung needs much time to decompose than poultry manure and therefore has a longer residual effect than poultry manure. Cow dung may have a longer stay to decomposition than poultry, hence the result. According to Zaman (2017), cow dung has been documented long as perhaps the best desired animal manures due to its high nutrient and organic matter content. The application of cow dung raises the organic carbon of degraded soils which may result in improving activity of beneficial soil microorganisms and the fertility of the soil by increasing availability of nutrients for plants from soil. According to the report of John et al., (2004), poultry manure contained essential nutrient elements associated with photosynthetic activities and thus promote roots and vegetative growth. Roy and Kashem (2014) also reported that cow dung resulted in significant increase in soil nitrogen and other soil properties necessary for crop yield and productivity. According to the report of Roy and Kashem (2014), adequate amounts of nitrogen may be obtained from reasonable amounts of organic matter applied to the soil and is directly responsible for vegetative growth of plants. Nitrogen functions in plants by being part of chlorophyll which is important in photosynthesis, and improves the quality of leaf (Roy and Kashem, 2014). According to the report of Patrick et al. (2012), yield of cabbage increased with increasing levels of nitrogen up to 390 kg/ha. Casely et al. (2006) observed that increasing rate of nitrogen (150-250 kg/ha) with basal P and K application increased yield of cabbage. The increase in water holding capacity in poultry manure and cow dung treatments also provided additional advantage for growth and yield to cabbage grown on such plots (Frempong et al.2006;Agyarko et al.2006;Ewulo, 2005).

Effect of soil amendment on yield components
The days to head initiation was significantly influenced by fertilizer and insecticide treatments in the 2015 experiment (Table 4). Head initiation for all treatments started 2 -3 weeks earlier than the control with poultry manure combined with neem or Cypermetrine producing the least days to head initiation. In 2016, days to cabbage head initiation ranged between 78 -97 days (Table 4). However, the production of cabbage without any form of fertilizer and insecticide application increased the number of days to head initiation by 10 to 19 days. The use of Poultry manure combined with neem or Cypermetrine required significantly less days (6-8days) to head initiation compared with NPK combined with Neem or Cypermetrine, cow dung combined with neem or foliar fertilizer combined with neem (Table 4).
Head diameter was also significantly influenced by the fertilizer and insecticide treatments (Tables 4). Poultry manure or cow dung regardless of the insecticide applied produced bigger cabbage heads which were 7 -7.4 cm bigger than the control.
Weight of head per plant produced was significantly affected by fertilizer and insecticide application with poultry manure combined with Cypermetrine significantly producing heavier head per plant than the control, or foliar combined with neem or Cypermetrine ( Table 4). The head per plant produced from the poultry manure combined with Cypermetrine were 0.80kg heavier than the control, foliar combined with Cypermetrine or neem (  Table 4). The use of Poultry manure combined with neem or Cypermetrine produced cabbage heads per plant that were 350 -450 % heavier than the cabbage heads of the control (0.20 kg). N.P.K combined with neem or Cypermetrine also produced heads that were 150 -315 % heavier than the control (Table 4).
Cabbage yield (tonnes per hectare) was significantly influenced by fertilizer and insecticide treatment in 2015 ( Table 4). The application of poultry manure and Cypermetrine or neem significantly produced 32.50 -37.23 tonnes (468 -537 %) more cabbage than the control. Foliar fertilizer regardless of the insecticide combined produced yields similar to the control (Table 4). In 2016, significantly higher yields of 278, 266, 289 and 131 % over the control (9 tonnes/ha) were recorded for poultry manure combined with neem, N.P.K (15:15:15) combined with neem, poultry manure combined with Cypermetrine, or cow dung combined with neem respectively over the control ( Table 4). The control or foliar combined with Cypermetrine recorded least yields of 10 and 9 tonnes/ha respectively (  The head weight and yield of cabbage treated to poultry manure, cow dung or NPK combined with Cypermetrine or neem are indicative of the fact that nutrient supply was better on with those treatments than the foliar application. It also raises the question whether nutrient absorption for plant use may be effectively done by the roots than the leaves. Fageria et al., (2009) confirmed that while soil uptake is more common and most effective, especially when nutrients are required in higher amounts and that in such situations foliar supply alone may not be enough to supply the needed amount. The control or foliar combined with Cypermetrine recording least yields of 10 and 9 tonnes/ha respectively could be that the foliar application of fertilizer had no effect on the yield of cabbage.