Pemupukan Fosfat dan Boron dalam Budidaya Jagung Manis di Tanah Masam: Respon Produksi dan Ketahanan terhadap Penyakit Bulai

Abstract

Tanaman membutuhkan asupan hara makro dan mikro esensial yang cukup dan berimbang untuk pertumbuhan normal dan produksi optimal. Pasokan hara yang kurang atau berlebih menyebabkan defisiensi atau keracunan yang mengakibatkan penurunan hasil dan kualitas tanaman. Selain itu, tanaman juga harus diproteksi dari serangan hama dan penyakit. Serangan jamur Peronosclerospora spp. penyebab penyakit bulai sering terjadi dalam budidaya jagung manis. Serangannya terjadi pada fase vegetatif dengan gejala lokal maupun sistemik, yaitu daun kerdil dan tampak kering serta tulang daun dan daun berwarna pucat hingga tanaman tidak dapat melangsungkan proses tumbuh normal. Selain berperan dalam proses transfer energi, fosfor (P) dalam bentuk senyawa fosfat memiliki fungsi fisiologis penting pada tingkat sel tanaman. Boron (B) merupakan hara mikro esensial bagi tumbuhan berpembuluh. Fungsi utama B pada tingkat molekuler adalah dalam proses ikatan silang pektin di dinding sel tanaman. Pengendalian penyakit tanaman yang disebabkan oleh jamur dengan cara kimia menggunakan fungisida berpotensi mencemari tanah dan dapat menimbulkan masalah lingkungan dan keamanan pangan. Oleh karena itu, pengendalian penyakit bulai melalui pemupukan P dan B dalam budidaya jagung manis diharapkan dapat menjadi alternatif solusi yang ramah lingkungan, selain untuk peningkatan produktivitas tanaman karena keduanya merupakan hara esensial. Fosfat alam sebagai pupuk P lebih mudah larut dan melepaskan P sebagai hara tersedia bagi tanaman di tanah masam. Tujuan penelitian ini adalah mengevaluasi pengaruh aplikasi fosfat alam dan boraks terhadap kadar P dan B tanah, serapan P dan B, produksi dan serangan bulai pada budidaya jagung manis pada tanah masam. Penelitian ini dilaksanakan pada Juni sampai Oktober 2022. Budidaya jagung manis dilakukan di Kebun Pendidikan Cikabayan, Departemen Ilmu Tanah dan Sumberdaya Lahan, Fakultas Pertanian, IPB. Analisis tanah dan tanaman dilakukan di Laboratorium Kimia dan Kesuburan Tanah, Fakultas Pertanian IPB menggunakan metode rutin. Percobaan menggunakan Rancangan Acak Kelompok dengan 6 taraf perlakuan aplikasi fosfat alam (FA) sebagai sumber P pada 4 kelompok dengan kadar B berbeda melalui aplikasi 4 taraf boraks (BR). Perlakuan FA (kg ha-1) terdiri atas Kontrol (tanpa FA), STD (213,04 fosfat alam impor dari Mesir sebagai rujukan), ½ FA (102,16), 1 FA (272,48), 1½ FA (442,76), dan 2 FA (613,04). Perlakuan boraks (kg ha-1) terdiri atas BR0 (tanpa boraks), BR1 (8), BR2 (16), dan BR3 (24). Pupuk dasar yang diaplikasikan meliputi 657 kg ha-1 ZA, 40 kg ha-1 SP-36, dan 180 kg ha-1 ZK. Peubah yang diamati meliputi produksi tanaman pada 10 MST, tinggi tanaman pada 2, 4, 6, dan 8 MST, persentase tanaman terserang bulai pada 4, 6, dan 8 MST, serapan P dan B daun, kadar klorofil daun, serta kadar P dan B tanah. Selain ANOVA dan DMRT, analisis data juga dilakukan untuk mengevaluasi hubungan dan pertautan antar peubah. Aplikasi FA berpengaruh nyata terhadap tinggi tanaman pada 8 MST. Tanaman tertinggi diperoleh pada perlakuan 1 FA dan berbeda nyata dengan kontrol, meskipun tidak berbeda nyata dengan perlakuan FA lainnya. Bobot tongkol segar sebagai peubah produksi berbeda nyata akibat perlakuan FA dan antar kelompok B. Produksi tertinggi diperoleh pada perlakuan 1½ FA, meskipun tidak berbeda nyata dengan taraf perlakuan STD, 1 FA, dan 2 FA. Dengan populasi 60 tanaman per petak, serangan bulai sudah teramati dengan jelas secara visual dan menyebar pada 4 MST. Peningkatan persentase tanaman terserang bulai pada 6 MST dan 8 MST berkisar 0 sampai 10%. Serapan P tanaman berbeda nyata akibat perlakuan FA, tetapi tidak berbeda nyata antar kelompok perlakuan BR. Kadar P daun atas dan bawah berbeda nyata akibat perlakuan FA. Kadar P tertinggi diperoleh pada perlakuan 1 FA di daun atas dan bawah. Berdasarkan posisi serta kadar B dan P daun, pada penelitian ini translokasi B tidak jelas teramati seperti halnya pada P. Serangan bulai mengakibatkan klorosis yang berkaitan dengan kadar klorofil daun. Berdasarkan kadar klorofil daun dan 6 kriteria yang ditetapkan, tingkat serangan bulai berbeda nyata antar perlakuan P maupun B. Berdasarkan analisis hubungan dan pertautan antar peubah, dalam penelitian ini terbentuk 23 persamaan dengan 9 persamaan berkoefisien korelasi atau determinasi nyata yang menjelaskan fungsi antara produksi dengan persentase serangan bulai, 4 fungsi terkait P, dan 4 fungsi terkait B. Dosis FA meningkatkan secara nyata dan linier P tanah. P tanah kemudian meningkatkan secara sangat nyata dan linier serapan P. Selanjutnya, serapan P menurunkan secara sangat nyata dan linier persentase serangan bulai dan serangan bulai menurunkan secara nyata produksi. Hal serupa diperoleh dari fungsi-fungsi terkait B.

In the cultivation of commercial crops, a sufficient and balanced input of essential macro- and micro-nutrients are required to obtain normal growth and optimum yield. Besides, the cultivated crop should be protected from pest and disease attack. An excessive or less nutrient supply causes toxicity or deficiency that results in crop yield and quality reduction. Infestation of Peronosclerospora spp. fungi is frequently reported in the cultivation of sweet corn. It occurs in the vegetative phase with local and systemic symptoms, namely stunted and dry-looking leaves with pale leaf veins and leaves that inhibit the crop to continue its growth processes normally. In addition to play a role in energy transfer processes, P has critical physiological functions at the cell state. Boron (B) is an essential micronutrient for vascular plants. The primary function of B at the molecular state is in the cross-linking process of pectin in the plant cell walls. Chemical control of plant diseases caused by fungi using fungicides has the potential to pollute soil and causes environmental and food safety problems. Therefore, controlling downy mildew desease by means of B and P fertilization in sweet corn cultivation is expected to be an alternative solution that is environmentally friendly, in addition to increasing plant productivity since both are essential nutrients. In acid soils, rock phosphate is more soluble and easily releases P as a bioavailable nutrient. This study aimed to evaluate the effects of rock phosphate and borax fertilization in suppressing downy mildew infestation and on P and B uptake and yield of sweet corn cultivated on an acid soil. This study was carried out from June to October 2022. The field experiment was done at the Cikabayan Experimental Station, Department of Soil Science and Land Resources, Faculty of Agriculture, IPB. Soil and plant analyses were conducted at the Soil Chemistry and Fertility Laboratory, Faculty of Agriculture, IPB. The experiment applied a randomized block design with six levels of applying rock phosphate (FA) application to six blocks differred in soil B status by applying four borax levels (BR). FA treatment (kg ha-1) consisted of Control (without FA), STD (213.04 imported FA from Egyp as reference), ½ FA (102.16), 1 FA (272.48), 1½ FA (442.76), and 2 FA (613.04), while borax treatment (kg ha-1) consisted of BR0 (without borax), BR1 (8), BR2 (16), and BR3 (24). Basal fertilization applied consisted of 657 kg ha-1 ZA, 40 kg ha-1 SP-36, and 180 kg ha-1 K2SO4. Vaiables observed were crop yield at 10 WAP, crop heigt at 2, 4, 6, and 8 WAP, persentage of the crop attacked by downy mildew at 4, 6, and 8 WAP, leaf uptake of P and B, leaf chlorophyle concentration, and soil P and B level. Data analyses were done on ANOVA, DMRT, and the relationship and correlation among the variables observed. Application of FA significantly affected plant height at 8 WAP. The highest plants were obtained in 1 FA treatment and significantly different from the control, although it was not significantly different from the other treatments. The cob fresh weigh as yield production variable was significantly different due to FA and BR treatments, the highest one was obtained in the 1½ FA treatment, although it was not significantly different from the STD, 1 FA, and 2 FA treatments. With a population of 60 plants per plot, downy mildew attack was already observed and spreaded at 4 WAP. The increase in percentage of plants attacked by downy mildew at 6 WAP and 8 WAP ranged from 0-10%. Leaf P uptake was significantly different due to FA treatments but not among BR treatments, in which P concentrations in the upper and lower leaves was significantly different. The highest one was obtained in 1 FA treatment in both the upper and lower leaves. Regarding the leaf position and B and P auptake, in this study translocation and accumulation of B was not clearly observed like those occuring on P. The downy mildew attack resulted in chlorosis that related to the leaf chlorophyle content. Based on the chlorophyle content and six selected criteria, the percentage of downy mildew attack was significantly different among the FA as well as BR treatments. Based on the relationships and correlation among the variable observed, it was obtained in this study 23 equations with 9 equations showing significant correlation or determination coefficient that explained the function between crop yield and percentage of downy mildew attack, 4 functions related to to P, and 4 functions related to B. The increasing dose of FA increased significantly and linearly soil P. Then, soil P increased very significantly and linearly P uptake. Furthermore, P uptake decreased significantly and linearly percentage of downy mildew attack and the later was decreased significantly the crop yield. The same results were obtained as related to B.